Tuning of the average p-d exchange in (Ga,Mn)As by modification of the Mn electronic structure -: art. no. 233201

An important parameter of the ferromagnetism of (Ga,Mn)As alloys is the average p-d exchange integral N(0)beta since the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction parameter J(RKKY)proportional to(N(0)beta)(2). We prove, by a detailed study of p-type Ga1-xMnxAs and n-type Ga1-xMnxAs:Te (x<0.005) in the paramagnetic phase, that the magnitude and sign of N(0)beta are strongly dependent on the local electronic configuration of the Mn ions. We find N(0)beta>0 (ferromagnetic coupling) in p-type samples where the local Mn configuration is Mn-Ga(0) (3d(5)+hole). In n-type samples, N(0)beta<0 (antiferromagnetic coupling) with the local Mn configuration being Mn-Ga(-) (3d(5)). The average N(0)beta in (Ga,Mn)As is not a material constant as widely believed. It can be tuned and can even change its sign, depending on the doping conditions of the Mn-containing layer.