Thickness dependent magnetic properties of (Ga,Mn)As ultrathin films

We report on a monotonic reduction of Curie temperature in dilute ferromagnetic semiconductor (Ga,Mn) As upon a well controlled chemical-etching/oxidizing thinning from 15 nm down to complete removal of the ferromagnetic response. The effect already starts at the very beginning of the thinning process and is accompanied by the spin reorientation transition of the in-plane uniaxial anisotropy. We postulate that a negative gradient along the growth direction of self-compensating defects (Mn interstitial) and the presence of surface donor traps gives quantitative account on these effects within the p-d mean field Zener model with adequate modifications to take a nonuniform distribution of holes and Mn cations into account. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4731202]