Effect of nitrogen incorporation in ferromagnetic (Ga,Mn)As epilayers

Abstract

Physical properties of ferromagnetic p-type Ga1−xMnxAs1−yNy epitaxial films (x=0.045 and y=0–0.032) grown by molecular-beam epitaxy are described. It is found that the incorporation of nitrogen gradually suppresses the metallic behavior of p-(Ga,Mn)As, especially at low temperatures. The Curie temperature TC decreases accordingly with increasing y value. The reduction in TC is discussed in terms of the suppression of hole-mediated long-range spin-exchange interaction due to the enhancement of carrier localization. Perpendicular magnetic anisotropy appears at the region around y=0.02, reflecting the reduced lattice constant due to substitutionally incorporated nitrogen. No significant change was found in the magnetic circular dichroism spectra in the photon energy region around the band gap of (Ga,Mn)As. Our experimental results show that the theoretical prediction based on the double exchange interaction [V. A. Dinh et al., Jpn. J. Appl. Phys., Part 2 42, L888 (2003)] is hardly materialized in this system.