Search NASA⌕ Search

Engineering topics

Zhai, Qiang

Publications and source records attributed to Zhai, Qiang.

Toward understanding the dimensional crossover of canonical spin-glass thin films

Spin-glass thin films exhibit many features different from the bulk. The freezing temperatures of spin-glass films are suppressed for reduced thickness and follow the Kenning relation. The dynamics are altered near the vacuum interface. These phenomena are closely related to the lower critical dimension of spin glasses, the spin-glass correlation length, and the dimensional crossover from d = 3 to d = 2. In this article, we review the experimental facts and theoretical perspectives for spin-glass thin films. We focus on canonical spin-glass systems with the Ruderman–Kittel–Kasuya–Yosida (RKKY) interaction between magnetic impurities in a nonmagnetic host. Open questions to be addressed are emphasized.

interfacial effects↗

Evidence for temperature chaos in spin glasses

We study the field cooled magnetization of a CuMn spin glass (SG) under temperature perturbations. The T-cycling curves are compared with the reference curve without temperature cycling. There is a crossover from the cumulative aging region to noncumulative aging region as the temperature change is increased. The cumulative aging range scales with the chaos length, ℓ c , becoming comparable to the correlation length, ξ, at the crossover boundary. The extracted chaos exponent, ζ=1.1, is in agreement with theoretical predictions. Furthermore, our results strongly suggest temperature chaos exists in real SG systems.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗