Spin orbit torques induced magnetization reversal through asymmetric domain wall propagation in Ta/CoFeB/MgO structures

Abstract

The magnetization reversal induced by spin orbit torques in the presence of Dzyaloshinskii-Moriya interaction (DMI) in perpendicularly magnetized Ta/CoFeB/MgO structures were investigated by using a combination of Anomalous Hall effect measurement and Kerr effect microscopy techniques. By analyzing the in-plane field dependent spin torque efficiency measurements, an effective field value for the DMI of ~300 Oe was obtained, which plays a key role to stabilize Néel walls in the film stack. Kerr imaging reveals that the current-induced reversal under small and medium in-plane field was mediated by domain nucleation at the edge of the Hall bar, followed by asymmetric domain wall (DW) propagation. However, as the in-plane field strength increases, an isotropic DW expansion was observed before reaching complete reversal. Micromagnetic simulations of the DW structure in the CoFeB layer suggest that the DW configuration under the combined effect of the DMI and the external field is responsible for the various DW propagation behaviors.

Efficient Spin‐Orbit Torque Switching of the Semiconducting Van Der Waals Ferromagnet Cr2Ge2Te6

“…As in the case discussed in the context of Figure c, clear SOT switching with the expected reversal of the hysteresis loop is observed in Figure a when sweeping H x under positive and negative charge current polarities at 4 K. Moreover, as expected from previous studies, higher charge currents require smaller H x and vice versa to change the magnetization of our CGT magnet with PMA (see Figure b). Note that too small I dc values result in incomplete (partial) reversal of the magnetization direction since in a large FM with a size of a few square micrometer, such as in our experiment, SOT switching is driven by domain nucleation . Furthermore, the low coercivity and low remanence in the magnetization loops of CGT films (Figure d) suggest that domain nucleation is easier for CGT films if compared to FMs such as CoFeB or TMIG that show sharp switching at coercivity.…”

Advanced Method for the Reliable Estimation of Spin-Orbit-Torque Efficiency in Low-Coercivity Ferromagnetic Multilayers

“…Considering the details of the magnetization reversal process of the Ru/Co/Ru sample, it can be noted that the domain growth takes place asymmetrically, and the domain wall itself has a smooth profile as compared with the sample containing the W layer. We assume that these features are associated with the presence of the largest Dzyaloshinskii-Moriya interaction in the sample [17]. In our previous study, the value of DMI D= 0.2 / 2 was measured [32].…”

“…In this paper, an alternative method of direct estimation of the SOT field in low-coercive structures by the position of a domain wall is proposed. In addition to SHE and RE, as a result of the passing of current through a Hall bar, the Oersted field is generated, which is responsible for initiating the reversal process [17,18]. Accounting for this field is especially important when considering systems with low coercive force.…”

Structure, Magnetic Property, Surface Morphology, and Surface Energy of Co40Fe40V10B10 Films on Si(100) Substrate

“…In spin-valve magnetic tunneling junctions (MTJs), CoFeB thin films can be sputtered into free or pinned layers, resulting in apparent tunneling magnetoresistance (TMR), perpendicular magnetic anisotropy (PMA), and soft ferromagnetic properties. The films can be applied for magnetoresistance random access memory (MRAM) and sensor components [9][10][11][12][13][14][15]. According to these properties, CoFeB films can be used to many kinds of spintronic devices.…”