Structure, magnetization, and low-temperature spin dynamic behavior of zincblende Mn-rich Mn(Ga)As nanoclusters embedded in GaAs

We have fabricated a set of samples of zincblende Mn-rich Mn(Ga)As clusters embedded in GaAs matrices by annealing (Ga,Mn)As films with different nominal Mn content at 650 degrees C. For the samples with Mn content no more than 4.5%, the Curie temperature reaches nearly 360 K. However, when Mn content is higher than 5.4%, the samples exhibit a spin-glass-like behavior. We suggest that these different magnetic properties are caused by the competing result of dipolar and Ruderman-Kittel-Kasuya-Yosida interaction among clusters. The low-temperature spin dynamic behavior, especially the relaxation effect, shows the extreme creeping effect which is reflected by the time constant tau of similar to 10(11) s at 10 K. We explain this phenomenon by the hierarchical model based on the mean-field approach. We also explain the memory effect by the relationship between the correlation function and the susceptibility.

National Natural Science Foundation of China 10674130 1071031560521001Major State Basic Research 2007CB924903 Chinese Academy of Sciences KJCX2. YW. W09-1 The authors acknowledge H. J. Meng, L. Chen, P. F. Xu, and S. Yan for their help on sample preparation and Y. Zhang and H. Y. Zhang for SQUID measurements. The authors also thank H. Z. Zheng and Y. T. Wang for valuable discussions. This work was supported partly by the National Natural Science Foundation of China under Grant Nos. 10674130, 10710315, and 60521001, the special funds for the Major State Basic Research under Contract No. 2007CB924903 of China, and the Knowledge Innovation Program Project of Chinese Academy of Sciences under Grant No. KJCX2. YW. W09-1.