Large nonlinear Hall effect in (FeCo)0:67Ge0:33/Ge heterojunctions

Abstract

The large nonlinear Hall effect was found in (FeCo)0:67Ge0:33/Ge heterojunctions formed by sputtering amorphous p-type (FeCo)0:67Ge0:33 magnetic semiconductor films on near intrinsic n-type Ge substrate. It is very interesting that the mechanisms of the large nonlinear Hall effect in (FeCo)0:67Ge0:33/Ge heterojunctions are different at different temperature ranges. Below 10 K, the Hall resistance of (FeCo)0:67Ge0:33/Ge heterojunctions is almost the same as the anomalous Hall effect of (FeCo)0:67Ge0:33 ferromagnetic films. While the temperature increased from 10 to 60 K, the nonlinear Hall resistance, longitudinal conductance, and magnetoresistance all increased quickly and reached the maximum at T=60 K. In this case, thermally excited conducting carriers can tunnel through the interfacial potential barrier in (FeCo)0:67Ge0:33/Ge heterojunctions. Thus, in the range of 10-60 K, the enhanced nonlinear Hall resistance can be attributed to the anomalous Hall effect which was further enhanced by interfacial Rashba spin-orbit coupling effect. When the temperature further increased from 60 to 250 K, the interfacial potential barrier weakened gradually, and the Hall resistance and magnetoresistance decreased due to the shunting of the Ge substrate. In this case, the nonlinear Hall effect of (FeCo)0:67Ge0:33/Ge heterojunctions can be explained very well by the two-band model of nonlinear Hall effect.