Dilute Magnetic Semiconductors Studied By Quantum Monte Carlo Simulation

In the past decade, enormous efforts have been put into the investigation of dilute magnetic semiconductors (DMS). The high-temperature ferromagnetism discovered in DMS provides the potential to systematically control both charge and spin degrees of freedom and thus opens new insight on combining spintronics with the well-established semiconductor technology.Despite intensive investigations of a decade, yet there is no single theory capable to consistently explain all the complex magnetic behaviors observed in DMS. The carrier mediated Ruderman-Kittle-Kasuya-Yosida (RKKY) interaction has been extensively studied and discussed, however, there are many contradictory conclusions and its validation has been highly doubt. On the one hand, the theory built on the RKKY model indeed gives excellent descriptions for the ferromagnetism, Curie temperature, transport, and even optical properties of some DMS materials, e.g., the prototypical DMS,(Ga,Mn)As and (Zn,Mn)Te. On the other hand, however, the RKKY model fails in many other materials, particularly, in the dilute magnetic oxides and nitrides, and its predicted high-temperature ferromagnetism in these materials has not yet been fully verified by experiments.In this paper, we use essentially exact Hirsh-Fye Quantum Monte Carlo simulation to study a modeled Dilute Magnetic Semiconductors system. The conclusions are as following:1) In intrinsic semiconductors system, the spin interactions are always ferromagnetic interaction and it decays exponentially with increasing the distance, which fit well into the framework of the RKKY interaction in a gaped system.2) In weak hybridization DMS system, although no definitely oscillatory behavior observed, it should be emphasized that the RKKY mechanism is still responsible because of the low carrier concentration.3) In strong hybridization DMS system, we found that the localized moment is not totally quenched and the partial localized moment is indeed formed from our calculations. However, the RKKY interaction is destroyed completely because of the strong hybridization and the long-range antiferromagnetic interaction is formed, which is in good agreement with previous studies about the strong sp-d hybridization DMSs system, such as oxides, nitrides and their multilayer systems with interlayer exchange coupling.