Magnetic and transport properties of amorphous Gdx Ge1-x alloys near the metal-insulator transition

E. Helgren, F. Hellman, Li Zeng, N. Sinenian, R. Islam, David Smith

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

The temperature and field dependence of magnetization and conductivity of amorphous Ge doped with Gd (a- Gdx Ge1-x) has been measured for a wide range of x (0.08<x<0.25) near the metal-insulator transition. Magnetization and magnetic susceptibility measurements show strong magnetic interactions and a low temperature spin-glass freezing. High field magnetization and susceptibility per Gd atom in the paramagnetic state are significantly suppressed below that of noninteracting Gd, as observed previously for a-Gd-Si alloys. However, unlike a-Gd-Si, the low field susceptibility does not fit a Curie-Weiss law and shows no significant dependence on composition. Conductivity measurements show that Gd causes localization of charge carriers below a characteristic temperature T*, which also marks the onset of significant negative magnetoresistance. Both T* and the magnitude of the MR are significantly lower in a-Gd-Ge than in comparable a-Gd-Si alloys. It is proposed that the large effects of the host matrix (Ge vs Si) are due to differences in both the band gap and dielectric constant, which cause changes in screening, thereby altering the effect of Gd magnetic moments on the localization of carriers and on the indirect mediated Gd-Gd exchange interactions.

Original languageEnglish (US)
Article number184440
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume76
Issue number18
DOIs
StatePublished - Nov 28 2007

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Metal insulator transition
Transport properties
Magnetization
Magnetic properties
transport properties
insulators
magnetic properties
magnetic permeability
metals
magnetization
Spin glass
Exchange interactions
Magnetoresistance
Magnetic moments
Charge carriers
Magnetic susceptibility
Freezing
conductivity
Temperature
Curie-Weiss law

ASJC Scopus subject areas

  • Condensed Matter Physics

Cite this

Magnetic and transport properties of amorphous Gdx Ge1-x alloys near the metal-insulator transition. / Helgren, E.; Hellman, F.; Zeng, Li; Sinenian, N.; Islam, R.; Smith, David.

In: Physical Review B - Condensed Matter and Materials Physics, Vol. 76, No. 18, 184440, 28.11.2007.

Research output: Contribution to journalArticle

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