Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

Ion irradiation of semiconductors is a well understood method to tune the carrier concentration in a controlled manner. For dilute magnetic semiconductors (DMS), the free carriers mediate the local magnetic moments and develop the long-range ferromagnetic coupling. Therefore, ion irradiation should provide a tool to engineer the magnetic properties of DMS. In this contribution, we show the possibility of fine tailoring the magnetism of highly conducting virgin GaMnAs films by ion irradiation. With increasing the displacement per atom (ion fluence), the GaMnAs films become more insulating step by step and only paramagnetic at the end. The coercivity can be increased by several times [1]. The approach can be used to tailor GaMnAs films with different coercivities, Curie temperatures (TC) as well as saturation magnetization. On the other hand one can use the approach to understand the conduction and magnetic coupling mechanism [2]. For relatively thick 25nm GaMnAs films with a high TC of 150 K [3] where the electrical gating is difficult due to the large hole concentration, ,we can decrease the hole concentration gradually. We found a linear dependence of Tc with increasing the compensation of holes by ion irradiation. This observation favours a valence band picture of ferromagnetic GaMnAs with high Mn concentrations.
1. L. Li, et al., J. Phys. D 44 099501 (2011);
2. T. E. Winkler, et al., Appl. Phys. Lett. 98, 012103 (2011).
3. Y. Nishitani, et al., Phys. Rev. B 81, 045208 (2010).