Spin-Orbit-Torque Switching of Noncollinear Antiferromagnetic Antiperovskite Manganese Nitride ${\mathrm{Mn}}_3\mathrm{Ga}\mathrm{N}$

Noncollinear antiferromagnets have promising potential for replacing ferromagnets in the field of spintronics as high-density devices with ultrafast operation. To take full advantage of noncollinear antiferromagnets in spintronics applications, it is important to achieve efficient manipulation of noncollinear antiferromagnetic spin. Here, using the anomalous Hall effect as an electrical signal of the triangular magnetic configuration, spin-orbit-torque switching with no external magnetic field is demonstrated in noncollinear antiferromagnetic antiperovskite manganese nitride ${\mathrm{Mn}}_3\mathrm{Ga}\mathrm{N}$ at room temperature. The pulse-width dependence and subsequent relaxation of Hall signal behavior indicate that the spin-orbit torque plays a more important role than the thermal contribution due to pulse injection. In addition, multistate memristive switching with respect to pulse current density is observed. The findings advance the effective control of noncollinear antiferromagnetic spin, facilitating the use of such materials in antiferromagnetic spintronics and neuromorphic computing applications.

Figure 1

(a) Out-of-plane and in-plane XRD profiles for MGN films around (002) and (200) peaks. (b) In-plane $\varphi$ scans of MGN films. (c) Temperature ($T$) dependence of the resistivity ${\rho }_{xx}$ and magnetization $M$ of MGN films. For the magnetization measurement, an external magnetic field ${\mu }_{0}H$ of 10 mT is applied parallel to the [001] direction. (d) Out-of-plane magnetic hysteresis loops and (e) anomalous Hall resistivity loops for MGN films at various temperatures. Inset of (e) is an enlargement of the anomalous Hall resistivity loop at 300 K. (f) Out-of-plane magnetization at 2 T and anomalous Hall resistivity ${\rho }_{xy,2\mathrm{T}}$ at 2 T for MGN films as a function of temperature. The inset presents the anomalous Hall resistivity at 300 K as a function of the $c/a$ ratio. The $c/a=0.9962$ film is 35-nm thick, while other films are 50-nm thick.

Figure 2

Sequential electrical current switching for (a) MGN/$\mathrm{Pt}$ and (b) MGN/$\mathrm{Ta}$ bilayers with no external magnetic field at room temperature. The current density $J$ is derived by the total thickness of the bilayers, and the current density through the HM layer $J_{\mathrm{HM}}$ is derived by HM thickness and the current through the HM layer as estimated using a parallel circuit model. In the same manner, ${\rho }_{xy}$ and ${\rho }_{xy,\mathrm{MGN}}$ are derived by the total thickness of bilayers and by MGN thickness and the current through the MGN layer.

Figure 3

(a) ${\rho }_{xy}$ as a function of $J$ observed for several pulse widths in MGN/$\mathrm{Ta}$ bilayers with no external magnetic field at room temperature. (b) Critical current density $J_c$ as a function of pulse width. The bold solid line is the result of a fit to a thermal activation model.

Figure 4

(a) Continuous write–read operations and subsequent relaxation measurements with no external magnetic field at room temperature. (b) Continuous write–read operation part from (a). The dashed lines are the results of a fit to the exponential decay function. (c) Relaxation measurement parts from (a). The bold solid lines are the results of a fit to the double-exponential function.

Figure 5

Dependence of ${\rho }_{xy}$–$J$ loops on $J_{\min }$ for MGN/$\mathrm{Ta}$ bilayers with no external magnetic field at room temperature.

Figure 6

(a) Hall resistivity ${\rho }_{xy}$ as a function of external magnetic field for MGN films ($c/a=0.9962$) before subtracting the ordinary Hall effect. (b) Temperature dependence of the Hall coefficient $R_H$.

Figure 7

Sample dependence of ${\rho }_{xy}$ switching width in SOT measurements for MGN(20 nm)/HM(3 bn) bilayers. MGN/$\mathrm{Pt}$ and MGN/$\mathrm{Ta}$ results presented in the main text are the devices $\mathrm{Pt}$1 and $\mathrm{Ta}$1, respectively. For $\mathrm{Pt}$2 device, ${\rho }_{xy,\mathrm{MGN}}$ is derived by assuming that the current flows through MGN and $\mathrm{Pt}$ in the same proportion as in $\mathrm{Pt}$1 device.

Figure 8

Hall and SOT measurements using the same SOT device. (a) $R_{xy}$ after subtracting estimated ordinary Hall effect versus external magnetic field of MGN/$\mathrm{Pt}$ bilayers. (b) $R_{xy}$ versus pulse number of MGN/$\mathrm{Pt}$ bilayers. All measurements are performed at room temperature using the same MGN/$\mathrm{Pt}$ Hall device. The data are reproduced from Appl. Phys. Lett. 115, 052403 (2019) [11], with the permission of AIP Publishing.