Rare Earth Iron Garnets Their Synthesis and Magnetic Properties Margret J. Geselbracht, Ann M. Cappellari, and Arthur B. ~llis' University of Wisconsin-Madison, Madison, WI 53706 Maria A. Rzeznik University of California Berkeley, Berkeley, CA 94720 Brian J. Johnson St. John's University, St. Joseph, MN 56374 The interaction of solids with magnetic fields is a topic that is discussed rarely in introductow chemistrv courses. This occurs in spite ofthe of magnetic materials in todav's societv. includine marmetic recordine media and data &rage. W;believeihat-a of the magnetic properties of solids fits well into the general chemistry course, because it provides a vehicle for discussing the existence of electrons, the electronic configurations of ions, and the role of solid state structure. Our experiment involving the preparation and study of a series of magnetic garnets with the composition Y,Gd3Pe5012 (0 < x < 3) that illustrates these topics follows. In addition, this experiment provides the opportunity to discuss the different types of magnetism in solids, to perform some chemistry using rare earth elements, and to learn about solid solutions and the tunability of properties by varying the composition of a solid solution. Furthermore, it can be performed in such a way that each student has a unique compound to prepare. The class data can then be compiled to obtain a picture of the magnetic properties of the entire range of composition of YrGd3.rFe5012. The majority of molecules and solids that we encounter are nonmagnetic. All of the electrons in these materials are paired, and the molecule or solid is said to be diamagnetic. The simplest type of magnetism, paramagnetism, often is demonstrated in introductory chemistry courses by observing the behavior of liquid oxygen in a magnetic field. Due to the presence of unpaired electrons in 02, the liquid is 'Author to whom correspondence should be addressed.
696
Journal of Chemical Education
attracted to a strong magnet, and if alarge horseshoe magnet is used, the liquid oxygen appears to hover, trapped between the poles of the magnet ( I ) . Many solids exhibit interesting magnetic behavior as well, often more complex than simple paramagnetism, due to the cooperative effect of many electrons in the solid acting in concert. Ferromagnetism is a property of solids that is technologically important and exploited in the use of permanent magnets, magnetic recording media, and
RdJenJum Description of the Morch 1994 Cover The cover of the March 1994 issue needsfurther amoliflcaton to be usefulfor teacners It snows a sampe ofz'nc roo on !he eh hands oe oftne page The bonom ponlon of the rod was etcneo oy human handing (In sport on of the rod was exposed as the rod was passed around classes over a period of several semesters; the top portion of the rod had a protective cover) and reveals the boundaries between differentgrains. As discussed in the accompanying paper (Geselbracht,M. J.; Ellis, A. B.; Penn, R. L.; Lisensky, G. C.; and Stone., D. S. J. Chem. Educ. 1994,71,254) the bubble raft on the right-hand side of the cover (also shown schematically in Figs. 2 and3 in the paper) provides a model for the grains, which are close-packed arrays of atoms having diflerent relative orientations.
