Structure-Property Relationships in Tb 4 PtGa 12 and Y 4 PtGa 12
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Structure-Property Relationships in Tb4PtGa12 and Y4PtGa12 Willa M. Williams,1 Han-Oh Lee,2 Monica Moldovan,3 Zachary Fisk,2 David P. Young,3 Julia Y. Chan1* 1
Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803 Department of Physics, University of California-Davis, Davis, CA, 95616 3 Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803 2
* To whom correspondence should be addressed E-mail: [email protected] Telephone: (225) 578-2695 Fax: (225) 578-3458 Abstract Single crystals of Y4PtGa12 have been synthesized and characterized by X-ray diffraction. The compound crystallizes in the cubic Im 3 m space group with lattice parameters a = 8.530(5) Å. Magnetic property measurements show that Y4PtGa12 does not order magnetically. Structure-property relationships with the isostructural antiferromagnet Tb4PtGa12 are discussed. Keywords: R4MGa12, Y4PtGa12, Tb4PtGa12, flux growth, single-crystal X-ray diffraction, magnetic susceptibility, cuboctahedra, gallides, rare earth intermetallics Introduction The use of molten gallium as a flux in crystal growth has attracted attention within the last decade[1-4]. Molten gallium as a solvent is advantageous due to the fact that it enhances diffusion of the elements and lowers the reaction temperatures [1,4,5,3]. In our investigation using molten gallium as a flux, we have discovered several intermetallic compounds. CePdGa6 is a heavy fermion metamagnet (γ ~ 230-360 mJ/mol K2), in which the Ce f-moments order antiferromagnetically along the c-axis at TN = 5.5 K. A reconfiguration of spins induces a ferromagnetic moment in the ab-plane [6]. Ce2PdGa12 orders antiferromagnetically at TN ~ 11 K, with a spin reconfiguration transition at 5 K, and has recently been compared to Ce2PdGa10, which exhibits large positive magnetoresistance of over 200% at low temperature [7]. We have also been investigating Sm and Tb intermetallics because of the possibility of mixed valency or other unusual magnetic or electronic behavior. SmPd2Ga2, of the ThCr2Si2 structure type, has been discovered to exhibit large positive magnetoresistance which increases by almost 100% at low temperature [8]. The crystal structure and transport measurements of polycrystalline R4MGa12 (R = GdLu; M = Ni, Pd) was first reported almost 20 years ago [9]. The structure of R4MGa12 (R = GdLu; M = Ni, Pd) belongs to the cubic I m 3 m space group and can be viewed as a redistributed homolog of U4Re7Si6-type [10]. The structure can also be regarded as the result of partially filling the octahedral voids in the cubic close packed AuCu3-type[11]. The electrical resistivity of R4MGa12 (R = Gd-Lu; M = Ni, Pd) shows metallic behavior [9]. Neutron and single crystal X-ray studies of RE4FeGa12-xGex (RE = Sm, Tb) reveal that these compounds crystallize in the cubic U4Re7Si6-type (I m 3 m) with lattice parameters a = 8.657(4) Å and 8.5620(9) Å for Sm and Tb analogs, respectively [5]. Tb4FeGa12-xGex orders
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antiferromagnetically at a Néel temperature of 13 K, while the is
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