Making and Breaking Covalent Bonds across the Magnetic Transition in the Giant Magnetocaloric Material Gd{sub 5}(Si{sub 2}Ge{sub 2})

Journal Article · Mon May 15 00:00:00 EDT 2000 · Physical Review Letters

DOI:https://doi.org/10.1103/PhysRevLett.84.4617· OSTI ID:20216590

Choe, W ^[1]; Pecharsky, V K ^[2]; Pecharsky, A O ^[2]; Gschneidner, Jr, K A ^[2]; Young, Jr, V G ^[3]; Miller, G J ^[1]

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1. Department of Chemistry, Iowa State University, Ames, Iowa 50011 (United States)
2. Ames Laboratory and Department of Materials Science and Engineering, Iowa State University, Ames, Iowa 50011 (United States)
3. Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455 (United States)

A temperature-dependent, single crystal x-ray diffraction study of the giant magnetocaloric material, Gd{sub 5}( Si{sub 2}Ge {sub 2}) , across its Curie temperature (276 K) reveals that the simultaneous orthorhombic to monoclinic transition occurs by a shear mechanism in which the (Si, Ge)- (Si, Ge) dimers that are richer in Ge increase their distances by 0.859(3) Angstrom and lead to twinning. The structural transition changes the electronic structure, and provides an atomic-level model for the change in magnetic behavior with temperature in the Gd{sub 5}( Si{sub x}Ge {sub 1-x}){sub 4} . (c) 2000 The American Physical Society.

• OSTI ID: 20216590
• Journal Information: Physical Review Letters, Vol. 84, Issue 20; Other Information: PBD: 15 May 2000; ISSN 0031-9007
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
30 DIRECT ENERGY CONVERSION
GADOLINIUM ALLOYS
SILICON ALLOYS
GERMANIUM ALLOYS
X-RAY DIFFRACTION
MONOCRYSTALS
CHEMICAL BONDS
CURIE POINT
PHASE TRANSFORMATIONS
TWINNING
CRYSTAL STRUCTURE
ELECTRONIC STRUCTURE
TEMPERATURE DEPENDENCE
MAGNETO-THERMAL EFFECTS
EXPERIMENTAL DATA