Magnetization switching of multi-state magnetic structures with current-induced torques

Abstract

Spintronic devices often require the ability to locally change the magnetic configuration of ferromagnetic structures on a sub-micron scale. A promising route for achieving this goal is the use of heavy metal/ferromagnetic heterostructures where current flowing through the heavy metal layer generates field-like and anti-damping like torques on the magnetic layer. Commonly, such torques are used to switch magnets with a uniaxial anisotropy between two uniformly magnetized states. Here, we use such torques to switch magnetization in Ta/Ni0.80Fe0.20 heterostructures with uniaxial and biaxial anisotropy, where in the latter the magnetization is non-uniform. The anisotropies are induced by shape and the magnetic state is monitored using the planar Hall effect. As structures with several easy axes induced by shape can be part of a magnetic memory element, the results pave the way for multi-level magnetic memory with spin-orbit torque switching.

Switching of multi-state magnetic structures via domain wall propagation triggered by spin-orbit torques

“…The spin Hall angle ( θ SH ) in such heterostructures is calculated and presented in details in our previous work ref. 31 which yields θ SH = 0.096. Here we note that while the reversible switching is performed in Device 1 by driving current in one arm, for Device 2 current is driven through different arms.…”

“…A comprehensive study of magnetic behavior of structures such as Device 1 and Device 2 were presented in ref. 31,33–35 respectively.…”

“…The current-induced switchings measurements are performed by driving current pulses of varying amplitude through one of the arms followed by measuring R PHE with a small probing current. We note that the switching current (I SW ) of Device 1 and 2 of ~2 mA corresponds to current density (J SW ) of 0.75 × 10 7 A/cm 2 through the Ta-layer, which is almost 2 times smaller than J SW needed to switch a single ellipse 31 , namely, the switching energetically more efficient (see supplementary materials for details). The spin Hall angle ( θ SH ) in such heterostructures is calculated and presented in details in our previous work ref.…”

“…In addition, SOTs have been used to systematically control domain wall motion for new classes of data, memory and logic devices 9,25–30 . In a recent report 31 we showed the efficiency of SOTs in inducing switchings in structures which exhibit non-uniform magnetization and effective shape-induced bi-axial magnetic anisotropy. These structures when used as one of the magnetic layers in a MTJ may pave the way for novel multi-level MRAM with efficient write operation based on SOTs.…”

Electric-field-assisted non-volatile magnetic switching in a magnetoelectronic hybrid structure

“…The repeatability of the angular TC loops was checked and illustrated in Figure S3 for the other hybrid devices (see details in the supplemental information ). The sharp switching between the stable magnetic states is favored in spintronic devices ( Das et al., 2018 ). In this MTJ/(011)-PMN-PT hybrid, the two distinct magnetic states can be sharply switched from 0° (inset on the bottom right of Figure 2 C to 180° [inset of the top left of Figure 2 C] and back using a larger H-field than the switching field.…”