Giant magnetoresistance in amorphous magnetic rare-earth silicon alloys (abstract)
- UCSD Physics Department, La Jolla, California 92093-0319 (United States)
We explore the influence of local magnetic moments on transport and magnetic properties in a new class of diluted magnetic semiconductors, amorphous RE{sub x}Si{sub 1{minus}x} (RE=Gd, or Tb, 0.1{lt}x{lt}0.15). As a comparison, nonmagnetic a-Y{sub x}Si{sub 1{minus}x} was also studied. The Gd, Tb, and Y ions have similar size and electronic structure, except for the 4f electrons in Gd and Tb. For 50 K{lt}T{lt}300 K, the conductivity {sigma} rises linearly with increasing T with nearly identical slopes for these three alloys. Below 50 K, they have dramatically different conductivities. a-Y{sub x}Si{sub 1{minus}x} shows the usual metal-to-insulator transition observed in doped semiconductors as the Y content is lowered. For a-Gd{sub x}Si{sub 1{minus}x} and a-Tb{sub x}Si{sub 1{minus}x}, however, {sigma} rapidly decreases such that compositions that are metallic in a-Y{sub x}Si{sub 1{minus}x} are insulating for a-Gd{sub x}Si{sub 1{minus}x} and a-Tb{sub x}Si{sub 1{minus}x}. Applying a magnetic field H has the usual relatively small effects on {sigma} of a-Y{sub x}Si{sub 1{minus}x} but produces a large {ital increase} in conductivity for the a-Gd{sub x}Si{sub 1{minus}x} alloys. For example, in a-Gd{sub 0.12}Si{sub 0.88}, {sigma} increases by 60 times at T=2.4 K and H=6 T. This giant negative magnetoresistance drops as T rises, disappearing above 50 K. Magnetization M as a function of H shows no hysteresis. M(H/T) for different fields and temperatures even for a single sample do not fit a Brillouin function, showing no paramagnetism or superparamagnetism. The magnetic susceptibility is much smaller than expected for isolated moments, indicating antiferromagnetic interactions between local moments. However, no Curie, Neel, or spin-glass freezing temperatures are observed. (Abstract Truncated)
- DOE Contract Number:
- FG03-95ER45529
- OSTI ID:
- 496604
- Report Number(s):
- CONF-961141--
- Journal Information:
- Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 8 Vol. 81; ISSN JAPIAU; ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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