New method for effective manipulation of the magnetism in (Ga, Mn)As films by organic molecules

In the case of III-V dilute magnetic semiconductors (DMS), the holes from Mn doping are known to mediate the ferromagnetic interaction among the Mn ions. Through modulation of the hole density, electrostatic gating has been shown to significantly alter the magnetic properties of (III, Mn)V films[1-3]. Here we demonstrate the manipulation of the magnetism of DMS (Ga, Mn)As. Mn-doped GaAs thin films with various thicknesses were grown by low-temperature molecular-beam epitaxy (LT-MBE), and organic charge-transfer molecules were deposited on the surface of (Ga, Mn)As films by either solution-based self-assembly or vacuum thermal evaporation, which led to large carrier density modulation, and significant changes in the Curie temperature (T_C) and magnetization (M_S). Electron donor (acceptor) molecules were found to decrease (increase) both T_C and M_s. Moreover, through proper preparation of the (Ga, Mn)As surface, self-assembled monolayer (SAM) patterns of organic molecules with sub-75 nanometer line width were successfully created via dip-pen nanolithography (DPN). These results could open a new pathway to control nanoscale manipulation of magnetism in DMS, with potential applications in reconfigurable, non-volatile and hybrid molecular nano-spintronics.