Article pubs.acs.org/IC
High-Pressure Synthesis, Crystal Structures, and Magnetic Properties of 5d Double-Perovskite Oxides Ca2MgOsO6 and Sr2MgOsO6 Yahua Yuan,*,†,‡ Hai L. Feng,*,†,‡,∥ Madhav Prasad Ghimire,§ Yoshitaka Matsushita,∇ Yoshihiro Tsujimoto,⊥ Jianfeng He,†,‡ Masahiko Tanaka,# Yoshio Katsuya,# and Kazunari Yamaura†,‡ †
Superconducting Properties Unit, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan Graduate School of Chemical Sciences and Engineering, Hokkaido University, North 10 West 8, Kita-ku, Sapporo, Hokkaido 060-0810, Japan § Condensed Matter Physics Research Center, Butwal, Rupandehi, Nepal ∇ Materials Analysis Station, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan ⊥ Materials Processing Unit, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan # Synchrotron X-ray Station at SPring-8, National Institute for Materials Science, Kohto 1-1-1, Sayo-cho, Hyogo 679-5148, Japan ‡
S Supporting Information *
ABSTRACT: Double-perovskite oxides Ca2MgOsO6 and Sr2MgOsO6 have been synthesized under high-pressure and high-temperature conditions (6 GPa and 1500 °C). Their crystal structures and magnetic properties were studied by a synchrotron X-ray diffraction experiment and by magnetic susceptibility, specific heat, isothermal magnetization, and electrical resistivity measurements. Ca 2 MgOsO 6 and Sr2MgOsO6 crystallized in monoclinic (P21/n) and tetragonal (I4/m) double-perovskite structures, respectively; the degree of order of the Os and Mg arrangement was 96% or higher. Although Ca2MgOsO6 and Sr2MgOsO6 are isoelectric, a magnetic-glass transition was observed for Ca2MgOsO6 at 19 K, while Sr2MgOsO6 showed an antiferromagnetic transition at 110 K. The antiferromagnetic-transition temperature is the highest in the family. A first-principles density functional approach revealed that Ca2MgOsO6 and Sr2MgOsO6 are likely to be antiferromagnetic Mott insulators in which the band gaps open, with Coulomb correlations of ∼1.8−3.0 eV. These compounds offer a better opportunity for the clarification of the basis of 5d magnetic sublattices, with regard to the possible use of perovskiterelated oxides in multifunctional devices. The double-perovskite oxides Ca2MgOsO6 and Sr2MgOsO6 are likely to be Mott insulators with a magnetic-glass (MG) transition at ∼19 K and an antiferromagnetic (AFM) transition at ∼110 K, respectively. This AFM transition temperature is the highest among double-perovskite oxides containing single magnetic sublattices. Thus, these compounds offer valuable opportunities for studying the magnetic nature of 5d perovskite-related oxides, with regard to their possible use in multifunctional devices.
1. INTRODUCTION Recently, double-perovskite oxides have attracted renewed attention, because they exhibit properties that may be useful for possible applications in, for example, multifunctional devices.1 Generally, stoichiometric A2BB′O6, wherein A denotes an alkaline-earth (or rare-earth) metal and B and B′ are d-block elements (or other metals), crystallizes in a cubic, tetragonal, or monoclinic double-perovskite structure with interpenetrating B and B′ face-centered cubic (FCC) sublattices. When B and B′ are both magnetic, interactions between the FCC cells result in useful magnetic features such as high spin-polarization at ambient temperature in Sr2FeMoO6,2 remarkable high-temperature (∼725 K) ferrimagnetism in Sr2CrOsO6,3 unusual competing spin structure in Sr2FeOsO6,4 chemical-pressureinduced high-temperature ferrimagnetism in Ca2FeOsO6,5 and © XXXX American Chemical Society
the coexistence of two independent magnetic orders in Sr2CoOsO6.6−8 These properties may be useful for developing advanced multifunctional devices; however, further clarification of the responsible mechanism is necessary. At present, the role of 5d electrons and the impact of interactions between 5d (or 4d) and 3d electrons on the properties are emerging issues. When B is nonmagnetic and B′ is magnetic, or vice versa, a single magnetic FCC sublattice is formed. The double perovskites containing single magnetic sublattices may be useful to investigate the emerging issues. They all display only antiferromagnetic characters with moderate magnetic interactions, as distances between the nearest-neighbor magnetic Received: December 25, 2014
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DOI: 10.1021/ic503086a Inorg. Chem. XXXX, XXX, XXX−XXX
Article
Inorganic Chemistry Table 1. Double-Perovskite Oxide with a Single Magnetic Sublatticea Magnetic Parameters d electron count, composition
space group
d3 d5 d5 d5 d5 d5 d5 d5 d5 d6 d7 d7 d7 d7 d7 d7 d8 d8 d8 d8
La2LiFe5+O6 LaBaMn2+NbO6 LaSrMn2+NbO6 LaCaMn2+NbO6 Ba2Mn2+WO6 Sr2Mn2+WO6 Ca2Mn2+WO6 Ba2Mn2+MoO6 Sr2Mn2+MoO6 Sr2Fe2+WO6 Ba2Co2+WO6 Sr2Co2+WO6 Ca2Co2+WO6 LaCaCo2+NbO6 Sr2Co2+TeO6 La2Co2+TiO6 Ba2Ni2+WO6 Sr2Ni2+WO6 Ca2Ni2+WO6 La2Ni2+TiO6
R3̅c
d1 d1 d3 d3 d3 d3 d3
Ba2YMoO6 La2LiMoO6 La2LiRu5+O6 La2NaRu5+O6 Sr2LuRu5+O6 Ba2YRu5+O6 Ba2LuRu5+O6
Fm3m ̅ P21/n P21/n P21/n P21/n Fm3̅m Fm3̅m
d1 d1 d1 d1 d2 d2 d2 d2 d2 d2 d3 d3 d3 d3 d3 d3 d3 d4 d5 d5
Ba2LiOs7+O6 Ba2NaOs7+O6 Sr2CaRe6+O6 Sr2MgRe6+O6 Ca3Os6+O6 Ba2CaOs6+O6 Sr2MgOs6+O6 Ca2MgOs6+O6 Ba2YRe5+O6 La2LiRe5+O6 La2NaOs5+O6 Ba2YOs5+O6 Ca2InOs5+O6 Sr2ZnIr6+O6 Sr2CaIr6+O6 Sr2MgIr6+O6 Ba2CaIr6+O6 La2LiIr5+O6 La2MgIr4+O6 La2ZnIr4+O6
Fm3m ̅ Fm3̅m P21/n I4/m P21/n Fm3̅m I4/m P21/n Fm3̅m P21/n P21/n Fm3m ̅ P21/n P21/n P21/n P21/n Fm3̅m (Pmm2) P21/n P21/n
P21/n Fm3m ̅ P42/n P21/n Fm3̅m P42/n P21/n Fm3̅m I4/m P21/n P21/n P21/n P21/n Fm3̅m I4/m P21/n P21/n
θW (K)
TN,f (K)
3d Double-Perovskite Oxides 10 −90 6.5 8.5 −35.7 9 45 −64.4 13 −71.3 45 −61.8
