Pressure-induced removal of magnetostructural inhomogeneity in Ge-rich Gd5(SixGe1x)4 giant magnetocaloric alloys

Y. C Tseng, D. Haskel, N. M. Souza-Neto, Ya. Mudryk, V. K. Pecharsky, and K. A. Gschneidner, Jr.
Phys. Rev. B 78, 214433 – Published 30 December 2008

Abstract

We investigate the emergence of ferromagnetism (FM) in low-Si-content Gd5(SixGe1x)4 alloys (x=0.025,0.05,0.075) from within the antiferromagnetic (AFM) phase of the Gd5Ge4 parent compound. X-ray magnetic circular dichroism (XMCD) and bulk magnetization measurements show that all samples exhibit partial FM order at low temperature, but their saturation magnetization is reduced relative to higher-Si-content samples (x=0.125,0.5). This reduced magnetization is due to an incomplete AFMorthorhombic(II)FMorthorhombic(I) magnetostructural phase transition upon cooling, as evidenced by x-ray diffraction. High-pressure XMCD measurements in a diamond-anvil cell show that applied pressures of 5.0, 3.0, and 2.0 GPa restore the full saturation magnetization in x=0.025, 0.05, and 0.075 samples, respectively, by stabilizing the FM-O(I) phase. The mixed-phase behavior is also evidenced in dTc/dP, which strongly varies with silicon concentration in these samples at low pressures but becomes independent of x at higher pressures where values typical of higher-x samples (0.125<x<0.5) are found.

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  • Received 24 October 2008

DOI:https://doi.org/10.1103/PhysRevB.78.214433

©2008 American Physical Society

Authors & Affiliations

Y. C Tseng1,2, D. Haskel2,*, N. M. Souza-Neto2, Ya. Mudryk3, V. K. Pecharsky3,4, and K. A. Gschneidner, Jr.3,4

  • 1Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60201, USA
  • 2Magnetic Materials Group, Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
  • 3Ames Laboratory, Iowa State University, Ames, Iowa 50011-3020, USA
  • 4Department of Materials and Engineering, Iowa State University, Ames, Iowa 50011-2300, USA

  • *haskel@aps.anl.gov

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Vol. 78, Iss. 21 — 1 December 2008

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