Structural, magnetic, and transport properties of laser-annealed GaAs:Mn-H

We have investigated the effect of laser annealing on the structural, magnetic, and transport properties of hydrogenated Ga 0.96 Mn 0.04 As films. Irradiation with nanosecond laser pulses leads to significant recovery of hole-mediated ferromagnetism in these films. By tuning processing parameters such as laser fluence and number of pulses, one can control the electrical and magnetic properties-namely, resistivity, magnetic coercivity, and remnant magnetization-in the laser-activated region. Ion-beam analysis indicates that the structural integrity of the film is maintained upon hydrogenation and laser annealing with evidence for displacement of substitutional Mn ions toward interstitial sites due to hydrogen-complex formation. Laser annealing results in the relaxation of up to 50% of Mn atoms back to substitutional sites while the Curie temperature recovers to ∼ 60 % of the T C prior to hydrogenation. Subsequent thermal annealing results in full relocation of Mn atoms to substitutional sites, yet the T C remains pinned at ∼ 60 % of its original value, suggesting the formation of a defect complex involving substitutional Mn. Our numerical simulations elucidate the strong interplay between laser processing parameters and Mn-H dissociation.