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          Institute: MPI für Festkörperforschung     Collection: FKF Publikationen 2006     Display Documents

ID: 273442.0, MPI für Festkörperforschung / FKF Publikationen 2006
Metal-nonmetal transition and colossal negative magnetoresistance in the gadolinium hydride halides GdIHx (0.67 < x < 1)
Authors:Ryazanov, M.; Kremer, R. K.; Simon, A.; Mattausch, Hj.
Date of Publication (YYYY-MM-DD):2006
Title of Journal:Physical Review B
Issue / Number:3
Sequence Number of Article:035114
Review Status:Peer-review
Audience:Not Specified
Abstract / Description:We report magnetization, specific heat, and resistivity measurements of
the metal-rich hydride halides YIHx and GdIHx (0.6 < x < 1.0) as a
function of temperature and applied magnetic field. A strong dependence
of the electrical and magnetic properties on the hydrogen content x is
observed. Isostructural nonmagnetic samples YIHx show metallic behavior
at room temperature with increased resistivity values as x approaches
its lower limit 0.61(3). Upon cooling, the resistivity passes through a
smooth minimum, suggesting a transition from an itinerant to a
localized electronic state at low temperatures. The presence of
magnetic Gd ions leads to significant changes of the electrical
transport properties and anomalous magnetic behavior. By reducing the
hydrogen content in GdIHx a metal-insulator transition occurs at a
critical concentration x=0.78(2). Magnetization and specific heat
measurements indicate competing ferromagnetic and antiferromagnetic
interactions which result in a partial antiferromagnetic ordering below
T-N, varying from 50 K for x=0.86 to 25 K for x=0.69, respectively. At
lower temperatures, the system GdIHx (x <= 0.78) exhibits
characteristics of a spin glass. For the semiconducting samples (x <=
0.78), a colossal negative magnetoresistance as large as 3 orders of
magnitude for x approximate to 0.7 is observed at 2 K. The metallic
GdIH0.86 phase exhibits a complex magnetoresistance which is positive
around the Neel temperature and becomes negative at temperatures well
below T-N. The observed correlations can be described in terms of a
mobility edge scenario and formation of bound magnetic polarons. To
gain a better insight into the electronic structure of LnIH first
principles tight-binding linear muffin-tin orbital
atomic-sphere-approximation band structure calculations have been
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Festkörperforschung
External Affiliations:Max Planck Inst Festkorperforsch, D-70569 Stuttgart, Germany.
Identifiers:ISI:000235009500055 [ID No:1]
ISSN:1098-0121 [ID No:2]
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