Abstract
We report the observation of current induced spin–orbit torque (SOT) switching of magnetization in a (Ga,Mn)(As,P) film using perpendicular magnetic anisotropy. Complete SOT switching of magnetization was achieved with current densities as low as 7.4 × 105 A/cm2, which is one to two orders of magnitude smaller than that normally used for SOT switching in ferromagnet/heavy metal bilayer systems. The observed magnetization switching chirality during current scans is consistent with SOT arising from spin polarization caused by the Dresselhaus-type spin–orbit-induced (SOI) fields. The magnitudes of effective SOI fields corresponding to the SOT were obtained from shifts of switching angles in angular dependent Hall measurements observed for opposite current polarities. By measuring effective SOI fields for the [11̄0] and the [110] current directions, we were then able to separate the values of the Dresselhaus-type (HeffD) and Rashba (HeffR) SOI fields. At a current density of 6.0 × 105 A/cm2, these values are HeffD=6.73Oe and HeffR=1.31Oe, respectively. The observed ratio of about 5:1 between Dresselhaus-type and Rashba SOI fields is similar to that observed in a GaMnAs film with an in-plane magnetic anisotropy.
Highlights
Significant advances have recently been made in the manipulation of magnetization by current instead of magnetic field.1–4 In such manipulation, it is required that the current is spin-polarized, so as to transfer spin angular momentum from the current to local magnetization
That the contribution of the cubic SOI term can be merged into the Rashba and Dresselhaus type SOI fields that are shown in Figs. 1(d) and 1(e)16 our experiment can only distinguish between fields through their dependence on current directions
We investigated the current-induced magnetization switching by spin–orbit torque (SOT) in a single layer of (Ga,Mn)(As,P) using perpendicular magnetic anisotropy
Summary
Significant advances have recently been made in the manipulation of magnetization by current instead of magnetic field. In such manipulation, it is required that the current is spin-polarized, so as to transfer spin angular momentum from the current to local magnetization. The best known mechanism in this context is the spin Hall effect, which produces a spin current perpendicular to the current direction Such a spin Hall effect originates from strong spin–orbit coupling and is quite large in heavy metals (HM) such as Pt, Ta, and W. In FM/HM bilayers, the structural asymmetry along the growth direction causes the Rashba effect, which can generate spin polarization of current carriers at the interface.. In FM/HM bilayers, the structural asymmetry along the growth direction causes the Rashba effect, which can generate spin polarization of current carriers at the interface.8,9 These two mechanisms are the major sources for achieving spin polarization of the current, which exerts spin–orbit torque (SOT) on the magnetization, and enables its manipulation. The degree of spin polarization and the spin current in a FM/HM bilayer are very sensitive to the properties of the FM/HM interface, and the SOT manipulation of magnetization is significantly affected by interface characteristics. the efficiency of the SOT in the FM/HM bilayer structures depends on the thicknesses of the two layers. In order to achieve more consistent SOT manipulation, it is, desirable to utilize simpler ferromagnetic systems, which are less sensitive to interface details and thicknesses of the structure
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