Asymmetry in the planar Hall resistance of Fe films grown on vicinal GaAs substrates

We have investigated the Hall effects of the ferromagnetic Fe films grown on standard (001) and on vicinal (i.e., slightly tilted toward the [110] direction) GaAs substrates at room temperature. While the symmetric hysteresis in the planar Hall resistance (PHR) is obtained from Fe film grown nominal (001) substrate, a significant asymmetry appeared in the Fe films grown on vicinal GaAs substrates. The asymmetry in the hysteresis of the PHR observed in the Fe film grown on vicinal surface originates from the switching of magnetization M between two easy axes while it is confined to the (001) crystal plane rather than to the film plane, thus involves both the planar Hall effect (PHE) and the anomalous Hall effect (AHE). The contribution of the AHE systematically increases as the tilted angle of the substrate increases. The asymmetric hysteresis of the PHR in the Fe films grown on the tilted substrate provides four distinct resistance states, which can be used for quaternary memory devices.