Discovery of Enhanced Magnetoelectric Coupling through Electric

Aug 16, 2017 - Particularly, a large electric field modulation of magnetic anisotropy (464 Oe) and FMR line width (401 Oe) is achieved at 173 K. The e...
10 downloads 10 Views 4MB Size
Download PDF
Discovery of Enhanced Magnetoelectric Coupling through Electric Field Control of Two-Magnon Scattering within Distorted Nanostructures Xu Xue,† Ziyao Zhou,*,† Guohua Dong,† Mengmeng Feng,† Yijun Zhang,† Shishun Zhao,† Zhongqiang Hu,† Wei Ren,† Zuo-Guang Ye,†,‡ Yaohua Liu,§ and Ming Liu*,† †

Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education & International Center for Dielectric Research, Xi’an Jiaotong University, Xi’an 710049, China ‡ Department of Chemistry and 4D LABORATORIES, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada § Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States S Supporting Information *

ABSTRACT: Electric field control of dynamic spin interactions is promising to break through the limitation of the magnetostatic interaction based magnetoelectric (ME) effect. In this work, electric field control of the two-magnon scattering (TMS) effect excited by in-plane lattice rotation has been demonstrated in a La0.7Sr0.3MnO3 (LSMO)/ Pb(Mn2/3Nb1/3)-PbTiO3 (PMN-PT) (011) multiferroic heterostructure. Compared with the conventional strain-mediated ME effect, a giant enhancement of ME effect up to 950% at the TMS critical angle is precisely determined by angular resolution of the ferromagnetic resonance (FMR) measurement. Particularly, a large electric field modulation of magnetic anisotropy (464 Oe) and FMR line width (401 Oe) is achieved at 173 K. The electric-field-controllable TMS effect and its correlated ME effect have been explained by electric field modulation of the planar spin interactions triggered by spin− lattice coupling. The enhancement of the ME effect at various temperatures and spin dynamics control are promising paradigms for next-generation voltage-tunable spintronic devices. KEYWORDS: magnetoelectric coupling, two-magnon scattering, spin waves, spin−lattice coupling, ferromagnetic resonance such as exchange bias and the charge screening effect,3−10 it has a longer effective thickness range for real ME applications. However, challenges remain in the strain-mediated ME effect, for example, further enhancing the ME coupling coefficient beyond fundamental limitations and solving the drawback of low-temperature failure problems of ferroelectrics.

M

ultiferroic composites or heterostructures with both ferromagnetic (FM) and ferroelectric (FE) phases, allowing electric field (E-field) control of magnetism or magnetic field (H-field) control of ferroelectricity through magnetoelectric (ME) coupling, are of great importance in the next-generation fast, compact, and energy-efficient microelectronic/spintronic industry.1−18 Particularly, the strain/ stress-mediated ME coupling effect,11−18 tuning magnetism through FM magnetostriction that couples to the E-field driving lattice deformation from the FE phase, is the most effective ME effect in multiferroic systems. Compared with other ME effects © 2017 American Chemical Society

Received: July 4, 2017 Accepted: August 16, 2017 Published: August 16, 2017 9286

DOI: 10.1021/acsnano.7b04653 ACS Nano 2017, 11, 9286−9293

Article

www.acsnano.org

Article

ACS Nano

Figure 1. (a) Topographic AFM image and (b) HRXRD pattern of the LSMO/PMN-PT (011) heterostructure. (c) Reciprocal space mapping (RSM) adjacent to the PMN-PT (222) reflection. (d) Cross section TEM image of LSMO/PMN-PT. (e) Cross-sectional STEM-HAADF image of the framed area in (d) viewed along the [100] zone axis of PMN-PT. The inset is a typical selected area electron diffraction pattern. (f) Magnification of the STEM-HAADF image of the framed area in (e) showing the in-plane rotation of the LSMO lattices. The bottom gives schematics of the LSMO structure and body spin-wave excitations between two boundaries with different wavelengths.

Pb(Mg2/3Nb1/3)-PbTiO3 (PMN-PT) (011) multiferroic heterostructures. The LSMO thin films with a structure of surface grain fluctuation and body lattice rotation have been explored to investigate the TMS effect due to the simultaneous excitations of surface spin waves (SSWs) and body spin waves (BSWs). We chose LSMO as a prototype material due to the strong interplay between spin, charge, orbital, and lattice degrees of freedom.36 The interfacial lattice distortions in LSMO disturb the long-range spin ordering, generate spin-wave scattering, and then change the FMR properties accordingly. Compared with the conventional strain-mediated ME effect, a giant enhancement of the ME effect up to 950% at the TMS critical angle (where the TMS intensity reaches a maximum) is obtained. By tuning the intrinsic spin interactions through planar lattice deformations, this electric field control of the TMS effect shows flexible spin-wave damping tuning in a ferromagnet. The outstanding FMR tunability and spin dynamics control are promising paradigms for next-generation voltage-tunable magnonic devices, where the spin wave serves as perfect information media with compactness and energy efficiency. From a nanotechnology perspective, the interfacial nanostructure establishment is a very effective method to generate spin-wave patterns as demanded. Additionally, electric field control of spin−lattice coupling may also contribute to other spintronic hotspots, where controlling the inner spin interactions is crucial, such as Skyrmions and Ruderman− Kittel−Kasuya−Yosida interactions.37,38

To break the bottleneck of the state-of-the-art multiferroics, manipulation of spin interactions is essential to generate electric-tunable spin dynamic behavior and enhance the ME coupling strength correspondingly with a wide workingtemperature window. The two-magnon scattering (TMS) is an important spin wave19−21 (quantized as magnons due to the dynamic eigenexcitations of ordered spins) dominated magnetic relaxtion mechanism for the limit of gigahertz excitations.22−33 The excitation sources could be the dynamic dipole fields associated with imperfect microstructures in crystals or effective field fluctuations associated with the magnetic anisotropy of randomly oriented grains. In other words, the zero-wave-vector (k = 0) magnons excited by ferromagnetic resonance (FMR) has been degenerated into spin-wave modes having k ≠ 0, providing a pathway for transferring energy from the uniform spin motions to the shortwavelength spin waves and resulting in a significant FMR field shift and FMR line width change. Previous research shows that the TMS phenomenon is almost universal in magnetic systems, including thin/thick-film ferromagnets,22−27 ultrathin ferromagnetic films,28−31 and superlattices.32,33 However, electric field modulation of the TMS effect has not been experimentally revealed. It had been demonstrated that the TMS effect and spin-wave resonances are both associated with spin exchange interactions.28,34 First-principles calculations indicate that a spin exchange interaction is nonlinearly correlative to interatomic distance, depending on the overlap of the atomic orbitals.35 Therefore, electric field control of the TMS effect is promising via manipulating spin−lattice coupling in a multiferroic system. An additional FMR field shift as well as line width change besides the conventional strain-mediated ME effect is expected. In the present work, electric field control of the TMS effect has been systemically studied in La0.7Sr0.3MnO3 (LSMO)/

RESULTS AND DISCUSSION The LSMO thin films were grown onto PMN-PT (011) substrates by the pulse laser deposition (PLD) method. The topography of the LSMO/PMN-PT (011) heterostructure was examined by atomic force microscopy (AFM) as displayed in 9287

DOI: 10.1021/acsnano.7b04653 ACS Nano 2017, 11, 9286−9293

Article

ACS Nano

Figure 2. Contour plots of the FMR absorption spectra when the magnetic field is parallel with the (100) plane of LSMO/PMN-PT (011) at (a) 300 K and (b) 173 K, respectively. Circles and arrows respectively label the two magnon scattering (TMS) positions and typical surfacespin-wave (SSW) and body-spin-wave (BSW) resonances. Angular dependence of electric field induced FMR field shifts measured at different temperatures when the magnetic field is 360° rotating within (c, e) the (100) plane and (d, f) the (0−11) plane of LSMO/PMN-PT (011). The inset shows schematically the sample under an electric field for angular dependence of FMR measurements, while the magnetic field is applied within the (100) plane (mode 1) or (0−11) plane (mode 2), and the microwave field is applied parallel to the [100] direction (mode 1) or [0−11] direction (mode 2).

Figure 1a, indicating granular thin film growth with a mean particle diameter of 40 nm and surface roughness of 2.9 nm. The high-resolution X-ray diffraction (HRXRD) pattern of LSMO/PMN-PT (011) confirms the LSMO film is single phase and exclusively (0ll) oriented (Figure 1b). The epitaxial structure was further examined by the reciprocal space map (RSM) around the (222) PMN-PT reflection, as shown in Figure 1c. The (222) spot of LSMO exhibits some extent of broadening along the in-plane direction, implying some variation in lattice constant a. From the spot center of the RSM, we can derive the LSMO lattice constant a of ∼0.388 nm and PMN-PT lattice constant a of ∼0.402 nm. The LSMO lattice is consistent with the bulk valve,36 indicating the LSMO thin film is fully relaxed on the PMN-PT substrate. Further insights into the LSMO/PMN-PT (011) microstructure were obtained by scanning transmission electron microscopy (STEM). The cross-sectional TEM image exhibits columnar growth of 50 nm LSMO with alternative light and dark contrast (Figure 1d). From the dark contrast, the portion of in-plane lattice rotation in LSMO could be estimated as less than 50%. As shown in Figure 1e, the cross-sectional high-angle annular dark-field (HAADF) image viewed along the [100] direction of PMN-PT reveals that the film is composed by an

alternative distribution of normal epitaxial and slight in-plane rotation of the lattices. The epitaxial strain in the LSMO/PMNPT (011) heterostructure is accommodated by slight in-plane rotating of the LSMO lattice (Figure S1 of the Supporting Information). A typical selected-area electron-diffraction (SAED) pattern (inset in Figure 1e) recorded at the overall LSMO/PMN-PT interface indicates a nice coherent stack of the LSMO and PMN-PT crystallographic planes. Figure 1f shows a magnified STEM-HAADF image of the framed area in Figure 1e and illustrates schematically the in-plane rotation of a pseudocubic perovskite cell of LSMO viewed along the [100] projection. Correspondingly, the bottom gives schematics of body spin-wave excitations between two boundaries with different wavelengths, where every spin will deviate from its initial equilibrium orientation to accommodate spin flip over the spin chain. From the volume perspective, we argue that the in-plane rotating lattices of LSMO could serve as the main scattering source in the TMS process. The surface grain fluctuation can minorly contribute to the TMS process due to the surface spin-wave excitations, which play an important role in ultrathin ferromagnetic films.28−31 A schematic of the FMR measurements is displayed in the inset of Figure 2, while the magnetic field direction is rotating 9288

DOI: 10.1021/acsnano.7b04653 ACS Nano 2017, 11, 9286−9293

Article

ACS Nano

Figure 3. Angular dependence of electric field induced FMR field shifts from both the strain effect and the two-magnon scattering effect at (a, b) 300 K and (c, d) 173 K, while the magnetic field is parallel with the (100) plane and (0−11) plane of LSMO/PMN-PT (011), respectively. The FMR field shift from each effect has been quantitively determined as labeled by arrows.

Figure 2a,b, the ΔH reaches its maximum at θH = 40° (300 K) and θH = 20° (173 K). This result indicates the TMS is both an angle- and temperature-related process, where degenerate spin waves are coupled with the FMR mode. It is clear that the FMR fields (Hr) at θH = 40° (300 K) and θH = 20° (173 K) are shifted close to the in-plane configurations (θH = 90°). This result is consistent with the orientation-dependent M−H loops, where the magnetization vector at the most intense TMS angle has been dragged to an in-plane configuration (Figure S2 of the Supporting Information). Angular dependence of electric field modulation of FMR spectra of LSMO/PMN-PT (011) is measured under two modes at 300 and 173 K, respectively (Figure S3 of the Supporting Information). We calculated the angular dependence of FMR field shifts (defined as δHr = Hr(E=20kv/cm) − Hr(E=0)) under polarized and unpolarized states (see Figure S4 of the Supporting Information). Figure 2c−f show the angular dependence of δHr when the magnetic field is 360° rotating within the (100) plane or (0−11) plane of the LSMO/PMNPT (011) heterostructure at 300 and 173 K, respectively. In previous works,14−18 the electric field modulation of FMR fields was ascribed to the electric field induced effective magnetic field (Heff) due to the strain-mediated ME coupling, and the maximum tunabilities are generally obtained at the in-plane configurations. However, Figure 2c−f indicate that the δHr shows 4-/2-fold-like anisotropy, which is very different from the traditional strain-mediated ME coupling.40 Poling of PMN-PT results in expansion of the (100) plane and constriction of the (0−11) plane of LSMO, which also leads to a two-way modulation of the FMR fields. Interestingly, the largest tunabilities are achieved at the TMS critical angles of 40°,

within the (100) plane (mode 1, φH = 90°) or (0−11) plane (mode 2, φ H = 0°) of the LSMO/PMN-PT (011) heterostructure. The microwave field direction is applied parallel to the [100] (mode 1) and [0−11] direction of PMN-PT, respectively. The in situ poling of PMN-PT (011) was achieved by applying an electric field along the [011] direction, using the LSMO film as the top electrode and a sputtered gold film as the bottom electrode. An electric field along the [011] direction of PMN-PT (0.3 mm) could generate an in-plane compressive strain along the [100] (d31 = −1800 pC N−1) direction and a tensile strain along the [0−11] (d32 = 900 pC N−1) direction, respectively. The strain propagating into the top LSMO layer results in an expanded (100) plane and a constricted (0−11) plane of LSMO, respectively. By changing the spatial symmetry of the scattering centers in LSMO, we could expect an anisotropic TMS response in these two modes. Figure 2a,b present contour plots of the FMR absorption spectra when the magnetic field is parallel with the (100) plane of LSMO/PMN-PT (011) at 300 and 173 K, respectively. Clear angular-resolving FMR absorption information, including FMR intensity, field, and line width, is observed. As shown in Figure 2a, the spin-wave resonances with both BSW and SSW modes are excited when the magnetic field approaches the outof-plane (θH = 0°),39 consistent with the microstructure of our LSMO thin films. At 173 K, the signals of BSWs and SSWs become extremely weak compared with the FMR modes, but the TMS effect at θH = 20° is significantly enhanced with an FMR line width (ΔH) of 1637 Oe (Figure 2b). According to previous works,26−30 the TMS effect can contribute to the ΔH broadening with strong anisotropic behavior. As shown in 9289

DOI: 10.1021/acsnano.7b04653 ACS Nano 2017, 11, 9286−9293

Article

ACS Nano

Figure 4. Angular dependence of electric field modulation of FMR line widths of LSMO/PMN-PT (011) at (a, b) 300 K and (c, d) 173 K, while the magnetic field is 360° rotating within the (100) plane and (0−11) plane of LSMO/PMN-PT (011), respectively. The largest FMR line width changes are observed at two-magnon scattering configurations. The inset shows schematically the sample under electric field for angular dependence of FMR measurements.

950%, 218%, and 573% as large as that of the conventional strain-mediated ME coupling (Figure 3a−d), indicating the great potential of TMS effect mediated ME coupling with a very wide working temperature range. According to Rodrigo Arias and D. L. Mills,28 the TMS effect contributes to the FMR field and line width changes are inversely proportional to the spin exchange stiffness D, which characterizes the magnon dispersion and is positively proportional to the exchange

140°, 220°, and 320° at 300 K and 20°, 160°, 200°, and 340° at 173 K except for Figure 2d, indicating that two kinds of ME effects compete in the system. The tunability at 173 K is about 1 order higher than that at 300 K due to much stronger spin interations in LSMO at low temperature.34 To quantitatively distinguish the TMS effect and strain effect mediated ME coupling in LSMO/PMN-PT (011), we consider that the electric field induced FMR field shifts consist of two main components when the magnetic field is applied in an intermediate angle between the in-plane and out-of-plane configurations. In that case, the expression of δHr is given by δHr = δHr(S) + δHr(T)

2JSa 2

integral J and lattice constant a, namely, D = h ,34 where S is the spin and h is the Planck constant. We argue that the electric field induced anisotropic planar lattice deformations of LSMO lead to increased or decreased spin interaction in different planes: J(E)(100) < J(0) < J(E)(0−11) Therefore, we have D(E)mode1 < D(0) < D(E)mode2, which explains the opposite trends of electric field control of the TMS effect in the (100) and (0−11) planes of the LSMO/PMN-PT (011) heterostructure. If the proposed mechanisms are effective, there shoud be consistency between the measured line width variations and the resonance field shifts. Figure 4 shows the angular dependence of FMR line widths of LSMO/PMN-PT (011) under both polarized and unpolarized states. It is well known that the TMS effect is reflected in the FMR line width. In this work, three contributions to the FMR line width are considered, which can be expressed as

(1)

The first term δH(S) corresponds to the conventional strain r effect mediated ME coupling contribution,14−18 and the second term δH(T) represents the TMS contribution. Therefore, the r δH(T) could be determined by deducting the strain component r from the total FMR field shift (see part 5 of the Supporting Information). Due to the strain transfer between in-plane and out-of-plane configurations, δH(S) r can be expressed as (S) (S) δHr(S)(θH ) = δHr,in (1 − cos θH ) + δHr,out cos θH

(2)

Figure 3a−d demonstrate the angular dependence of δHr that comes from the two effects at 300 and 173 K, showing a strong anisotropy for both effects in the two modes. The average δH(T) values at the TMS angles are calculated to be r −62, 57, −238, and 562 Oe, as shown in Figure 3a−d, respectively. Quantitatively, the TMS contribution is 163%,

ΔH = ΔH (G) + ΔH (I) + ΔH (T) 9290

(3) DOI: 10.1021/acsnano.7b04653 ACS Nano 2017, 11, 9286−9293

Article

ACS Nano

Figure 5. (a) Temperature dependence of the FMR fields of LSMO/PMN-PT (011) under both polarized and unpolarized states when the magnetic field is parallel with the (100) plane at 0°, 20°, and 90°, respectively. The largest splitting of the FMR field is observed at θH = 20° when the temperature is below 250 K. The inset shows the corresponding electric field induced FMR field shifts at three magnetic field directions. (b) FMR field and line width responses under bipolar sweeping of the electric field at θH = 20° and 173 K.

The first term represents the intrinsic Gilbert damping, which is proportional to the microwave frequency.23 Therefore, the Gilbert damping is electric field uncorrelated at the given microwave excitation frequency. The second term is the inhomogeneous line width broadening resulting from the inhomogeneity of the films. For inhomogeneous films one expects a larger inhomogeneous broadening at the out-of-plane configuration compared to the in-plane configuration, which shows that ΔH(θH = 0°) > ΔH(θH = 90°).30 For our films it shows that ΔH(θH = 0°) ≪ ΔH(θH = 90°), which indicates that the inhomogeneous line width broadening can be eliminated. The last term is the contribution due to the TMS effect. Obviously, the TMS effects contributing to ΔH in the two modes are opposite. As shown in Figure 4a,c, an enhanced TMS effect is excited by the electric field, as evidenced by the increase of ΔH. At the critical TMS angles (40°, 140°, 220°, and 320° at 300 K; 20°, 160°, 200°, and 340° at 173 K), the mean increase of ΔH is 43 and 162 Oe (Figure 4a,c), respectively. Correspondingly, in mode 2 the electric field results in a decrease of ΔH by 47 and 384 Oe at 300 and 173 K (Figure 4b,d), repectively. The tunability of the FMR line width in the two modes is calculated to be 11.1% and −10.4% at 300 K and 11.2% and −23.6% at 173 K, respectively (Figure S5 of the Supporting Information). The changes in ΔH indicate the TMS effect becomes tunable through changing the intrinsic spin interaction by spin−lattice coupling. In other words, the density of degenerate spin-wave states can be controlled via altering the planar lattice deformations of a ferromagnet. Figure 5a represents the temperature-dependent Hr of LSMO/PMN-PT (011) under both polarized and unpolarized states when the magnetic field is parallel with the (100) plane at 0°, 20°, and 90°, respectively. The magnetic anisotropy disappears upon increasing the temperature to 360 K, indicating a ferromagnetic to paramagnetic phase transition (T C ) of LSMO. The inset of Figure 5a shows the corresponding electric field induced FMR field shifts. It is clear that the tunibility is near zero around TC. When the temperature drops to below 250 K, the δHr is dramatically increased at θH = 20° with respect to the other two configurations, indicating tremendous potential of the twomagnon scattering effect mediated ME coupling at low temperatures. This strong ME coupling at low temperatures could be explained by the enhanced spin interactions of LSMO

at low temperatures.34 At θH = 20°, as shown in Figure 5b, the FMR field and line width response to bipolar sweeping of the electric field displays butterfly-like curves with two big jumps near the coercive field of ±6.7 kV/cm. Therefore, the electric field control of the TMS effect is directly relevant to nonlinear lattice deformations arising from the ferroelastic domain switching of the PMN-PT (011) substrate.15,16 These findings point to the fact that the TMS-mediated ME effect in a ferromagnet can be flexibly controlled via strain engineering below TC. In addition, the TMS-mediated ME effect works even at a very low electric field with very good reliability (Figure S6 of the Supporting Information). The outstanding ME effect promises functional device paradigms such as voltage-tunable microwave devices. This concept can be extended to various ferromagnetic systems that intrinsically possess the TMS effect to explore optimized ME performance.

CONCLUSIONS In summary, the electric field control of the TMS effect has been demonstrated in the LSMO/PMN-PT (011) heterostructure with in-plane lattice rotation as scattering source. The TMS effect shows strong anisotropic and temperature-dependent behaviors via angular dependence of ferromagnetic resonance measurements. A large electric field modulation of magnetic anisotropy and ferromagnetic resonance line width at the critical TMS angles was achieved at different temperatures. The tunabilities of TMS intensity are quantitatively determined to be −10.4−11.1% at 300 K and −23.6−11.2% at 173 K, respectively. The TMS effect has been quantitatively decoupled from the strain effect, indicating a dramatic enhancement of ME effect with a very wide working-temperature range. The electric-field-controllable TMS effect and its correlated ME effect are associated with electric field modulation of the planar spin interactions triggered by spin−lattice coupling. The further development of the voltage control of the TMS effect is promising for manipulating spin dynamics in spintronic devices. METHODS Sample Fabrication. The LSMO (La0.7Sr0.3MnO3) thin films were deposited on (011)-oriented single-crystalline PMN-PT substrates [5 mm (L) × 4 mm (W) × 0.3 mm (T)] by pulsed laser deposition, with an O2 partial pressure of 30 Pa and a substrate temperature of 700 °C. The energy density and pulse frequency were 1.5−2.5 J/cm2 and 3 Hz, 9291

DOI: 10.1021/acsnano.7b04653 ACS Nano 2017, 11, 9286−9293

Article

ACS Nano respectively. After the deposition, the as-grown thin films were in situ annealed for 30 min, then cooled to room temperature under the same O2 partial pressure with a cooling rate of 20 °C/min. Microstructural Characterization. A high-resolution X-ray diffractogram with θ−2θ scanning and reciprocal space mapping (PANalytical, X’Pert MRD) and an atomic force microscope (Bruker Dimension Inc.) were used to characterize the crystallinity, epitaxial nature, and surface morphology of the LSMO/PMN-PT (011) heterostructure. The microstructure of the film was characterized by STEM (JEOL JEM-ARM 200F) with a probe spherical aberration corrector. The robe size and semiconvergence angle were 0.1 nm and α = 32 mrad, and the collection angle interval was between 80 and 170 mrad during the experiments. Magnetic Property Measurement. The M−H hysteresis loops of the sample were measured by a vibrating sample magnetometer (Lake Shore 7404). An X-band (9.3 GHz) electron paramagnetic resonance system was used for ferromagnetic resonance measurements. The sample was placed in a rectangular cavity working at the TE102 mode with a 360° rotating base. Temperature can be automatically controlled by the software, and angular-dependent FMR measurements were conducted manually. E-field-tuning FMR was explored by in situ poling the LSMO/PMN-PT (011) heterostructure along the thickness direction with Au as eletrodes.

REFERENCES (1) Ojha, S.; Nunes, W. C.; Aimon, N. M.; Ross, C. A. Magnetostatic Interactions in Self-Assembled CoxNi1‑xFe2O4/BiFeO3 Multiferroic Nanocomposites. ACS Nano 2016, 10, 7657−7664. (2) Tian, G.; Zhang, F.; Yao, J.; Fan, H.; Li, P.; Li, Z.; Song, X.; Zhang, X.; Qin, M.; Zeng, M.; Zhang, Z.; Yao, J.; Gao, X.; Liu, J. Magnetoelectric Coupling in Well-Ordered Epitaxial BiFeO3/ CoFe2O4/SrRuO3 Heterostructured Nanodot Array. ACS Nano 2016, 10, 1025−1032. (3) Chu, Y. H.; Martin, L. W.; Holcomb, M. B.; Gajek, M.; Han, S. J.; He, Q.; Balke, N.; Yang, C. H.; Lee, D.; Hu, W.; et al. Electric-Field Control of Local Ferromagnetism using a Magnetoelectric Multiferroic. Nat. Mater. 2008, 7, 478. (4) Béa, H.; Bibes, M.; Ott, F.; Dupé, B.; Zhu, X. H.; Petit, S.; Fusil, S.; Deranlot, C.; Bouzehouane, K.; Barthélémy, A. Mechanisms of Exchange Bias with Multiferroic BiFeO3 Epitaxial Thin Films. Phys. Rev. Lett. 2008, 100, 017240. (5) Wu, S. M.; Cybart, S. A.; Yu, P.; Rossell, M. D.; Zhang, J. X.; Ramesh, R.; Dynes, R. C. Reversible Electric Control of Exchange Bias in a Multiferroic Field-Effect Device. Nat. Mater. 2010, 9, 756. (6) Molegraaf, H. J.; Hoffman, J.; Vaz, C. A.; Gariglio, S.; Van Der Marel, D.; Ahn, C. H.; Triscone, J. M. Magnetoelectric Effects in Complex Oxides with Competing Ground States. Adv. Mater. 2009, 21, 3470−3474. (7) Hu, J. M.; Nan, C. W.; Chen, L. Q. Size-Dependent Electric Voltage Controlled Magnetic Anisotropy in Multiferroic Heterostructures: Interface-Charge and Strain Comediated Magnetoelectric Coupling. Phys. Rev. B: Condens. Matter Mater. Phys. 2011, 83, 134408. (8) Cai, T.; Ju, S.; Lee, J.; Sai, N.; Demkov, A. A.; Niu, Q.; Li, Z.; Shi, J.; Wang, E. Magnetoelectric Coupling and Electric Control of Magnetization in Ferromagnet/Ferroelectric/Normal-Metal Superlattices. Phys. Rev. B: Condens. Matter Mater. Phys. 2009, 80, 140415. (9) Duan, C. G.; Jaswal, S. S.; Tsymbal, E. Y. Predicted Magnetoelectric Effect in Fe/BaTiO3 Multilayers: Ferroelectric Control of Magnetism. Phys. Rev. Lett. 2006, 97, 047201. (10) Maruyama, T.; Shiota, Y.; Nozaki, T.; Ohta, K.; Toda, N.; Mizuguchi, M.; Tulapurkar, A. A.; Shinjo, T.; Shiraishi, M.; Mizukami, S.; Ando, Y.; Suzuki, Y. Large Voltage-Induced Magnetic Anisotropy Change in a Few Atomic Layers of Iron. Nat. Nanotechnol. 2009, 4, 158−161. (11) Yang, S. W.; Peng, R. C.; Jiang, T.; Liu, Y. K.; Feng, L.; Wang, J. J.; Chen, L. Q.; Li, X. G.; Nan, C. W. Non-Volatile 180° Magnetization Reversal by an Electric Field in Multiferroic Heterostructures. Adv. Mater. 2014, 26, 7091−7095. (12) Liu, M.; Obi, O.; Lou, J.; Chen, Y.; Cai, Z.; Stoute, S.; Espanol, M.; Lew, M.; Situ, X.; Ziemer, K. S.; Harris, V. G.; Sun, N. X. Giant Electric Field Tuning of Magnetic Properties in Multiferroic Ferrite/ Ferroelectric Heterostructures. Adv. Funct. Mater. 2009, 19, 1826− 1831. (13) Zhang, S.; Zhao, Y.; Xiao, X.; Wu, Y.; Rizwan, S.; Yang, L.; Li, P.; Wang, J.; Zhu, M.; Zhang, H.; Jin, X.; Han, X. Giant Electrical Modulation of Magnetization in Co40Fe40B20/Pb(Mg1/3Nb2/3)0.7Ti0.3O3 (011) Heterostructure. Sci. Rep. 2014, 4, 3727. (14) Lou, J.; Liu, M.; Reed, D.; Ren, Y.; Sun, N. X. Giant Electric Field Tuning of Magnetism in Novel Multiferroic FeGaB/Lead Zinc Niobate−Lead Titanate (PZN-PT) Heterostructures. Adv. Mater. 2009, 21, 4711−4715. (15) Liu, M.; Howe, B. M.; Grazulis, L.; Mahalingam, K.; Nan, T.; Sun, N. X.; Brown, G. J. Voltage-Impulse-Induced Non-Volatile Ferroelastic Switching of Ferromagnetic Resonance for Reconfigurable Magnetoelectric Microwave Devices. Adv. Mater. 2013, 25, 4886− 4892. (16) Liu, M.; Zhou, Z.; Nan, T.; Howe, B. M.; Brown, G. J.; Sun, N. X. Voltage Tuning of Ferromagnetic Resonance with Bistable Magnetization Switching in Energy-Efficient Magnetoelectric Composites. Adv. Mater. 2013, 25, 1435−1439. (17) Li, P.; Chen, A.; Li, D.; Zhao, Y.; Zhang, S.; Yang, L.; Liu, Y.; Zhu, M.; Zhang, H.; Han, X. Electric Field Manipulation of Magnetization Rotation and Tunneling Magnetoresistance of Mag-

ASSOCIATED CONTENT S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsnano.7b04653. Some additional data about TEM microstructural analysis (1); voltage control of FMR spectra (2); orientation dependence of magnetic hysteresis loops (3); angular dependence of FMR fields under both polarized and unpolarized states (4); quantification of TMS-mediated ME coupling (5); tunability of the TMS mechanism in the two modes (6); reliability of electric field control of the TMS effect (7) (PDF)

AUTHOR INFORMATION Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected]. ORCID

Ziyao Zhou: 0000-0002-5484-5442 Zuo-Guang Ye: 0000-0003-2378-7304 Yaohua Liu: 0000-0002-5867-5065 Ming Liu: 0000-0002-6310-948X Notes

The authors declare no competing financial interest.

ACKNOWLEDGMENTS The work was supported by the Natural Science Foundation of China (Grant Nos. 51472199, 11534015, and 51602244), the National 111 Project of China (B14040), the 973 Program (Grant No. 2015CB057402), and the Fundamental Research Funds for the Central Universities. The authors appreciate the support from the International Joint Laboratory for Micro/ Nano Manufacturing and Measurement Technologies. Z.Z. and M.L. are supported by the China Recruitment Program of Global Youth Experts. Z.-G.Y. acknowledges support from the Natural Sciences and Engineering Research Council of Canada. Y.L. was supported by the Division of Scientific User Facilities of the Office of Basic Energy Sciences, U.S. Department of Energy. 9292

DOI: 10.1021/acsnano.7b04653 ACS Nano 2017, 11, 9286−9293

Article

ACS Nano

Wave Stiffness and Anisotropy Field. Phys. Rev. B: Condens. Matter Mater. Phys. 2007, 76, 184413. (35) Wang, H.; Ma, P. W.; Woo, C. H. Exchange Interaction Function for Spin-Lattice Coupling in bcc Iron. Phys. Rev. B: Condens. Matter Mater. Phys. 2010, 82, 144304. (36) Majumdar, S.; van Dijken, S. Pulsed Laser Deposition of La1−xSrxMnO3: Thin-Film Properties and Spintronic Applications. J. Phys. D: Appl. Phys. 2014, 47, 034010. (37) Rohart, S.; Miltat, J.; Thiaville, A. Path to Collapse for an Isolated Néel Skyrmion. Phys. Rev. B: Condens. Matter Mater. Phys. 2016, 93, 214412. (38) Hosseini, M. V.; Askari, M. Ruderman-Kittel-Kasuya-Yosida Interaction in Weyl Semimetals. Phys. Rev. B: Condens. Matter Mater. Phys. 2015, 92, 224435. (39) Yu, J. T.; Turk, R. A.; Wigen, P. E. Exchange-Dominated Surface Spin Waves in Thin Yttrium-Iron-Garent Films. Phys. Rev. B 1975, 11, 420. (40) Nan, T.; Zhou, Z.; Liu, M.; Yang, X.; Gao, Y.; Assaf, B. A.; Lin, H.; Velu, S.; Wang, X.; Luo, H.; Chen, J.; Akhtar, S.; Hu, E.; Rajiv, R.; Krishnan, K.; Sreedhar, S.; Heiman, D.; Howe, B. M.; Brown, G. J.; Sun, N. X. Quantification of Strain and Charge Co-Mediated Magnetoelectric Coupling on Ultra-Thin Permalloy/PMN-PT Interface. Sci. Rep. 2014, 4, 3688.

netic Tunnel Junctions at Room Temperature. Adv. Mater. 2014, 26, 4320−4325. (18) Liu, M.; Hoffman, J.; Wang, J.; Zhang, J.; Nelson-Cheeseman, B.; Bhattacharya, A. Non-Volatile Ferroelastic Switching of the Verwey Transition and Resistivity of Epitaxial Fe3O4/PMN-PT (011). Sci. Rep. 2013, 3, 1876. (19) Nozaki, T.; Shiota, Y.; Miwa, S.; Murakami, S.; Bonell, F.; Ishibashi, S.; Kubota, H.; Yakushiji, K.; Saruya, T.; Fukushima, A.; Yuasa, S.; Shinjo, T.; Suzuki, Y. Electric-Field-Induced Ferromagnetic Resonance Excitation in an Ultrathin Ferromagnetic Metal Layer. Nat. Phys. 2012, 8, 492. (20) Collet, M.; De Milly, X.; Kelly, O. D. A.; Naletov, V. V.; Bernard, R.; Bortolotti, P.; Ben Youssef, J.; Demidov, V. E.; Demokritov, S. O.; et al. Generation of Coherent Spin-Wave Modes in Yttrium Iron Garnet Microdiscs by Spin-Orbit Torque. Nat. Commun. 2016, 7, 10377. (21) Chumak, A. V.; Vasyuchka, V. I.; Serga, A. A.; Hillebrands, B. Magnon Spintronics. Nat. Phys. 2015, 11, 453. (22) Azevedo, A.; Oliveira, A. B.; De Aguiar, F. M.; Rezende, S. M. Extrinsic Contributions to Spin-Wave Damping and Renormalization in Thin Ni50Fe50 Films. Phys. Rev. B: Condens. Matter Mater. Phys. 2000, 62, 5331. (23) Lindner, J.; Barsukov, I.; Raeder, C.; Hassel, C.; Posth, O.; Meckenstock, R.; Landeros, P.; Mills, D. L. Two-Magnon Damping in Thin Films in Case of Canted Magnetization: Theory versus Experiment. Phys. Rev. B: Condens. Matter Mater. Phys. 2009, 80, 224421. (24) Zakeri, K.; Lindner, J.; Barsukov, I.; Meckenstock, R.; Farle, M.; Von Hörsten, U.; Wende, H.; Keune, W.; Rocker, J.; Kalarickal, S. S.; Lenz, K.; Kuch, W.; Baberschke, K.; Frait, Z. Spin Dynamics in Ferromagnets: Gilbert Damping and Two-Magnon Scattering. Phys. Rev. B: Condens. Matter Mater. Phys. 2007, 76, 104416. (25) Mizukami, S.; Ando, Y.; Miyazaki, T. Effect of Spin Diffusion on Gilbert Damping for a Very Thin Permalloy Layer in Cu/Permalloy/ Cu/Pt Films. Phys. Rev. B: Condens. Matter Mater. Phys. 2002, 66, 104413. (26) Srivastava, A. K.; Hurben, M. J.; Wittenauer, M. A.; Kabos, P.; Patton, C. E.; Ramesh, R.; Dorsey, P. C.; Chrisey, D. B. Angle Dependence of the Ferromagnetic Resonance Linewidth and Two Magnon Losses in Pulsed Laser Deposited Films of Yttrium Iron Garnet, MnZn Ferrite, and NiZn Ferrite. J. Appl. Phys. 1999, 85, 7838−7848. (27) Hurben, M. J.; Patton, C. E. Theory of Two Magnon Scattering Microwave Relaxation and Ferromagnetic Resonance Linewidth in Magnetic Thin Films. J. Appl. Phys. 1998, 83, 4344−4365. (28) Arias, R.; Mills, D. L. Extrinsic Contributions to the Ferromagnetic Resonance Response of Ultrathin Films. Phys. Rev. B: Condens. Matter Mater. Phys. 1999, 60, 7395. (29) Landeros, P.; Arias, R. E.; Mills, D. L. Two Magnon Scattering in Ultrathin Ferromagnets: The Case Where the Magnetization Is Out of Plane. Phys. Rev. B: Condens. Matter Mater. Phys. 2008, 77, 214405. (30) Beaujour, J. M.; Ravelosona, D.; Tudosa, I.; Fullerton, E. E.; Kent, A. D. Ferromagnetic Resonance Linewidth in Ultrathin Films with Perpendicular Magnetic Anisotropy. Phys. Rev. B: Condens. Matter Mater. Phys. 2009, 80, 180415. (31) Urban, R.; Woltersdorf, G.; Heinrich, B. Gilbert Damping in Single and Multilayer Ultrathin Films: Role of Interfaces in Nonlocal Spin Dynamics. Phys. Rev. Lett. 2001, 87, 217204. (32) Lindner, J.; Lenz, K.; Kosubek, E.; Baberschke, K.; Spoddig, D.; Meckenstock, R.; Pelzl, J.; Frait, Z.; Mills, D. L. Non-Gilbert-Type Damping of the Magnetic Relaxation in Ultrathin Ferromagnets: Importance of Magnon-Magnon Scattering. Phys. Rev. B: Condens. Matter Mater. Phys. 2003, 68, 060102. (33) Lenz, K.; Wende, H.; Kuch, W.; Baberschke, K.; Nagy, K.; Jánossy, A. Two-Magnon Scattering and Viscous Gilbert Damping in Ultrathin Ferromagnets. Phys. Rev. B: Condens. Matter Mater. Phys. 2006, 73, 144424. (34) Golosovsky, M.; Monod, P.; Muduli, P. K.; Budhani, R. C. SpinWave Resonances in La0.7Sr0.3MnO3 Films: Measurement of Spin9293

DOI: 10.1021/acsnano.7b04653 ACS Nano 2017, 11, 9286−9293