skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: The effect of hydrostatic pressure upon the magnetic transitions in the Gd(sub 5)(Si(sub x)Ge(sub 1-x))(sub 4) giant magnetocaloric compounds : x-ray magnetic circular dichroism study.

Abstract

No abstract prepared.

Authors:
; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
920976
Report Number(s):
ANL/XSD/JA-59372
Journal ID: ISSN 0163-1829; PRBMDO; TRN: US200805%%2
DOE Contract Number:
DE-AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Phys. Rev. B; Journal Volume: 76; Journal Issue: 2007
Country of Publication:
United States
Language:
ENGLISH
Subject:
36 MATERIALS SCIENCE; HYDROSTATICS; MAGNETIC CIRCULAR DICHROISM; GADOLINIUM ALLOYS; SILICON ALLOYS; GERMANIUM ALLOYS; PRESSURE DEPENDENCE; MAGNETIC PROPERTIES; PHASE TRANSFORMATIONS

Citation Formats

Tseng, Y. C., Haskel, D., Lang, J. C., Sinogeikin, S., Mudryk, Ya., Pecharsky, V. K., Gschneidner, K. A., Northwestern Univ., and Iowa State Univ. The effect of hydrostatic pressure upon the magnetic transitions in the Gd(sub 5)(Si(sub x)Ge(sub 1-x))(sub 4) giant magnetocaloric compounds : x-ray magnetic circular dichroism study.. United States: N. p., 2007. Web. doi:10.1103/PhysRevB.76.014411.
Tseng, Y. C., Haskel, D., Lang, J. C., Sinogeikin, S., Mudryk, Ya., Pecharsky, V. K., Gschneidner, K. A., Northwestern Univ., & Iowa State Univ. The effect of hydrostatic pressure upon the magnetic transitions in the Gd(sub 5)(Si(sub x)Ge(sub 1-x))(sub 4) giant magnetocaloric compounds : x-ray magnetic circular dichroism study.. United States. doi:10.1103/PhysRevB.76.014411.
Tseng, Y. C., Haskel, D., Lang, J. C., Sinogeikin, S., Mudryk, Ya., Pecharsky, V. K., Gschneidner, K. A., Northwestern Univ., and Iowa State Univ. Mon . "The effect of hydrostatic pressure upon the magnetic transitions in the Gd(sub 5)(Si(sub x)Ge(sub 1-x))(sub 4) giant magnetocaloric compounds : x-ray magnetic circular dichroism study.". United States. doi:10.1103/PhysRevB.76.014411.
@article{osti_920976,
title = {The effect of hydrostatic pressure upon the magnetic transitions in the Gd(sub 5)(Si(sub x)Ge(sub 1-x))(sub 4) giant magnetocaloric compounds : x-ray magnetic circular dichroism study.},
author = {Tseng, Y. C. and Haskel, D. and Lang, J. C. and Sinogeikin, S. and Mudryk, Ya. and Pecharsky, V. K. and Gschneidner, K. A. and Northwestern Univ. and Iowa State Univ.},
abstractNote = {No abstract prepared.},
doi = {10.1103/PhysRevB.76.014411},
journal = {Phys. Rev. B},
number = 2007,
volume = 76,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • X-ray magnetic circular dichroism (XMCD) measurements and density functional theory (DFT) are used to study the electronic conduction states in Gd{sub 5}(Ge{sub 1-x}Si{sub x}){sub 4} materials through the first-order bond-breaking magnetostructural transition responsible for their giant magnetocaloric effect. Spin-dependent hybridization between Ge 4p and Gd 5d conduction states, which XMCD senses through the induced magnetic polarization in Ge ions, enables long-range Ruderman-Kittel-Kasuya-Yosida ferromagnetic interactions between Gd 4f moments in adjacent Gd slabs connected by Ge(Si) bonds. These interactions are strong below but weaken above the Ge(Si) bond-breaking transition that destroys 3D ferromagnetic order.
  • Future advancements in magnetocaloric refrigeration/heat pumping technologies depend on the discovery of new materials that demonstrate large, tunable magnetocaloric effects (MCEs) in the vicinity of coupled magnetic and structural phase transitions that occur reversibly with minimum hysteresis. Here, with this in mind, we investigate phase transitions, microstructure, magnetic, thermal, magnetocaloric, and transport properties of (Gd 5-xSc x)Si 1.8Ge 2.2 compounds. Replacement of magnetic Gd with non-magnetic Sc in Gd 5-xSc xSi 1.8Ge 2.2 increases the ferromagnetic to paramagnetic first order phase transition temperature, T C, with only a minor reduction in MCE when x ≤ 0.2. We also demonstrate thatmore » hydrostatic pressure further increases T C and reduces the hysteresis of the first order phase transition in Gd 4.8Sc 0.2Si 1.8Ge 2.2 from 7 to 4 K. Temperature-dependent x-ray powder diffraction study of Gd 4.8Sc 0.2Si 1.8Ge 2.2 confirms the monoclinic ↔ orthorhombic structural transformation at T C, in agreement with magnetic, calorimetric, and electrical transport measurements. In addition to the substantial magnetocaloric effect, a large magnetoresistance of ~20% is also observed in Gd 4.8Sc 0.2Si 1.8Ge 2.2 for ΔH = 50 kOe in the vicinity of the magnetostructural transition. Finally, in a drastic reversal of the initial doping behavior further additions of Sc (x > 0.2) suppress formation of the monoclinic phase, change the nature of the transition from first-to second-order, and reduce both the transition temperature and magnetocaloric effect.« less
  • The heat capacity measured in an adiabatic heat pulse calorimeter with nonzero heat capacity suffers from intrinsic errors in the vicinity of a first order phase transition. When these errors are carried over into the calculation of the magnetocaloric effect, the latter also suffers from large systematic errors. The sources of the intrinsic errors in the heat capacity near the first order phase transition temperature and the procedures to minimize them are discussed. The experimental heat capacity data of Gd{sub 5}(Si{sub 2}Ge{sub 2}) and ultra pure Dy, both of which exhibit first order phase transition, are used to confirm themore » theoretical conclusions. {copyright} {ital 1999 American Institute of Physics.}« less
  • Temperature-dependent, single crystal and powder X-ray diffraction studies as well as magnetization, and heat capacity measurements were carried out on two phases of the Gd{sub 5}Ga{sub x}Ge{sub 4-x} system: for x=0.7 and 1.0. Gd{sub 5}Ga{sub 0.7}Ge{sub 3.3} shows three structure types as a function of temperature: (i) from 165 K to room temperature, the orthorhombic Sm{sub 5}Ge{sub 4}-type structure exists; (ii) below 150 K, it transforms to a orthorhombic Gd{sub 5}Si{sub 4}-type structure; and (iii) a monoclinic Gd{sub 5}Si{sub 2}Ge{sub 2}-type component is observed for the intermediate temperature range of 150 K<=T<=165 K. This is the first time that allmore » these three structure types have been observed for the same composition. For Gd{sub 5}Ga{sub 1.0}Ge{sub 3.0}, the room temperature phase belongs to the orthorhombic Pu{sub 5}Rh{sub 4}-type structure with interslab contacts between main group atoms of 2.837(4) A. Upon heating above 523 K, it transforms to a Gd{sub 5}Si{sub 4}-type structure with this distance decreasing to 2.521(7) A before decomposing above 573 K. - Graphical Abstract: Phase transformations in Gd{sub 5}Ga{sub x}Ge{sub 4-x} magnetocaloric materials as a function of temperature.« less
  • The effect of hydrostatic pressure on the ferromagnetic ordering transition of the monoclinic Gd{sub 5}(Si{sub 0.375}Ge{sub 0.625}){sub 4} giant magnetocaloric effect compound was investigated using x-ray magnetic circular dichroism measurements in a diamond anvil cell. The Curie temperature T{sub C} increases linearly with applied pressure up to {approx}7.2 GPa, at which point a discontinuity in dT{sub c}/dP occurs. This discontinuity, which appears when T{sub C} reaches {approx}277 K, is also observed when the unit cell volume is reduced by Si doping and is associated with the volume-driven monoclinic (M) to orthorhombic [O(I)] structural transition.