Pressure-induced removal of magnetostructural inhomogeneity in Ge-rich Gd-5(SixGe1-x)(4) giant magnetocaloric alloys

TitlePressure-induced removal of magnetostructural inhomogeneity in Ge-rich Gd-5(SixGe1-x)(4) giant magnetocaloric alloys
Publication TypeJournal Article
Year of Publication2008
AuthorsTseng YC, Haskel D, Souza-Neto NM, Mudryk Y, Pecharsky VK, Gschneidner KA
Journal TitlePhysical Review B
Volume78
Pages214433
Date Published12
ISBN Number1098-0121
Accession NumberISI:000262244400078
Keywordsantiferromagnetic materials, ferromagnetic materials, ferromagnetic-antiferromagnetic transitions, gadolinium alloys, ge-si alloys, high-pressure effects, magnetic circular dichroism, magnetisation, magnetocaloric effects, solid-state phase transformation
Abstract

We investigate the emergence of ferromagnetism (FM) in low-Si-content Gd-5(SixGe1-x)(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 AFM orthorhombic(II)-> FM orthorhombic(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 dT(c)/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.

URL<Go to ISI>://000262244400078
DOI10.1103/Physrevb.78.214433