Noncollinear Antiferromagnetic Spintronics

Conceptual schematics for some major exotic physical phenomena and spin manipulation methods relevant to noncollinear antiferromagnetic spintronics.

(a) The magnetization (M) curves and (b) the Hall conductivity (σ_H) versus the applied field (B) at 300 K of Mn₃Sn measured in B || [2$ \stackrel{\mathrm{-}}{\text{1}}\stackrel{\mathrm{-}}{\text{1}} $0], [01$ \stackrel{\mathrm{-}}{\text{1}} $0] and [0001].^[27] Copyright 2015, Springer Nature.

(a) Scanning electron microscope image of the spin-accumulation device. The red dashed line denotes the Mn₃Sn single crystal while the blue square is the ferromagnetic NiFe electrode. The non-magnetic Cu leads are indicated by the brown areas. (b) Schematic of the measurement geometry. The electrical current (I) was applied along [2$ \stackrel{\mathrm{-}}{\text{1}}\stackrel{\mathrm{-}}{\text{1}} $0] while the external magnetic field (B) was applied within the basal plane of the device and the field angle θ was measured from [01$ \stackrel{\mathrm{-}}{\text{1}} $0]. When the spin accumulation generated by the injected I at Mn₃Sn surfaces has a component parallel to the NiFe magnetization, the electrochemical potential across the Mn₃Sn/NiFe interface is supposed to be changed and a voltage between the NiFe and Cu electrodes will be induced. (c,d) Resistance (ΔR) measured between the NiFe and Cu electrodes versus B at room temperature. The Mn₃Sn had been magnetically saturated by a large B of −0.75 T and +0.75 T before the measurement in (c) and (d), respectively. The insets show the corresponding magnetic order of Mn₃Sn; blue arrows represent Mn sublattice moments.^[51] Copyright 2019, Springer Nature.

(a) The optical photo of the Mn₃Sn/nonmagnetic layer (Pt, W, or Cu) devices (left) and the schematic of spin-orbit-torque (SOT) switching (right). Write and read currents and the magnetic bias field (${\;\mu _0}{H_x} $) are applied along the x direction. The spin-polarized currents along the z direction (green arrows on yellow spheres) in Pt generated by the write current can exert SOTs on the cluster magnetic octupole (orange arrow) of Mn₃Sn and result in the switching of the polarization axis. (b) Hall voltage (V_H) versus write currents (I_write) for a Mn₃Sn/Pt (7.2 nm) device under ${\;\mu _0}{H_x} $ = ±0.1 T. (c) V_H (top) and I_write (bottom) for the same device measured at room temperature and under ${\;\mu _0}{H_x} $ = 0.1 T. V_H measured by a read current of 0.2 mA changes its sign depending on the polarity of the I_write pulse with a duration of ~100 ms. The switching of V_H is performed for 200 times. (d) I_write-dependent $\;\mu {\rm{V}} $ for the same device measured at room temperature under ${\mu _0}{H_x} $ = 0.1 T. The magnitude of the switching of $\;\mu {\rm{V}} $ is affected by the minimum write current ($ {\textit{I}}_{\text{write}}^{\text{min}} $).^[78] Copyright 2020, Springer Nature.

(a) The schematic of the polarization-resolved measurement setup. WGP denotes the wire-grid polarizer. (b) The real- and imaginary-part of the Hall conductivity (σ_xy) spectra for Mn_3+xSn_1−x films. The solid curves display the low-frequency THz-time-domain spectroscopy for x = 0.02 on a SiO₂ substrate while the open circles show the broadband spectrum for x = 0.08 on a Si substrate. Reproduced under terms of the CC-BY license.^[116] Copyright 2020, Springer Nature.