Diluted magnetic semiconductors: effects of positional disorder

Abstract

The effects of positional disorder of the magnetic impurities on the magnetic behaviour of diluted magnetic semiconductors such as (Cd,Mn)Te and (Ga,Mn)As is analyzed using simple effective models. We describe some of the techniques that have been applied successfully to such systems, such as mean-field approximations, random-phase approximations and Monte Carlo simulations. Disorder is shown to have observable consequences for the shape of the magnetization curve. Below the critical temperature, the magnetization is spatially inhomogeneous, leading to very unusual temperature and magnetic field dependence of the average magnetization. The spin-wave spectrum is also affected and both localized and extended spin-wave modes are found.

Acknowledgments

I gratefully acknowledge collaborations with R.N. Bhatt, Malcolm P. Kennett, Adel Kassaian, Chenggang Zhou and Xin Wan. This work was supported by NSERC of Canada.