Intrinsically limited critical temperatures of highly doped Ga1−xMnxAs thin films
Résumé
Ga1−xMnxAs films with exceptionally high saturation magnetizations of 100 emu/cm3 corresponding to effective Mn concentrations of xef f 0.10 still have a Curie temperature TC smaller than 195 K contradicting mean-field predictions. The analysis of the critical exponent of the remnant magnetization-- =0.407 5 --in the framework of the models for disordered /amorphous ferromagnets suggests that this limit on TC is intrinsic and due to the short range of the ferromagnetic interactions resulting from the small mean-free path of the holes. This result questions the perspective of room-temperature ferromagnetism in highly doped GaMnAs.