Increased Efficiency of Current‐Induced Motion of Chiral Domain Walls by Interface Engineering

Abstract

Magnetic racetrack devices are promising candidates for next‐generation memories. These spintronic shift‐register devices are formed from perpendicularly magnetized ferromagnet/heavy metal thin‐film systems. Data are encoded in domain wall magnetic bits that have a chiral Néel structure that is stabilized by an interfacial Dzyaloshinskii–Moriya interaction. The bits are manipulated by spin currents generated from electrical currents that are passed through the heavy metal layers. Increased efficiency of the current‐induced domain wall motion is a prerequisite for commercially viable racetrack devices. Here, significantly increased efficiency with substantially lower threshold current densities and enhanced domain wall velocities is demonstrated by the introduction of atomically thin 4d and 5d metal “dusting” layers at the interface between the lower magnetic layer of the racetrack (here cobalt) and platinum. The greatest efficiency is found for dusting layers of palladium and rhodium, just one monolayer thick, for which the domain wall's velocity is increased by up to a factor of 3.5. Remarkably, when the heavy metal layer is formed from the dusting layer material alone, the efficiency is rather reduced by an order of magnitude. The results point to the critical role of interface engineering for the development of efficient racetrack memory devices.

Giant Spin Hall Effect and Spin–Orbit Torques in 5d Transition Metal–Aluminum Alloys from Extrinsic Scattering

“…The SOT is known to be very sensitive to the detailed structure of the interface between the SOT layer and the magnetic layer. [ 33 ] For example, as shown in Figure 3f, 2 Å thick Ir or Al layers inserted at this interface significantly changes the dependence of v on the current density. The insertion of the Al dusting layer results in a lower terminal value of v ≈ 200 m s –1 while J c does not change.…”

Spin-orbit torque switching of magnetic tunnel junctions for memory applications

“…Notably, contrary to STT-driven DW that move only with electron flow, SOT-driven DW move in the direction imposed by the sign of 𝑩 , and by the interplay of DMI and 𝐵 . This opens the very interesting possibility of optimizing and manipulating DW motion not only for switching, but also for racetrack memories and domain wall logic applications [96][97][98][99][100][101][102].…”

Ultrafast racetrack based on compensated Co/Gd-based synthetic ferrimagnet with all-optical switching

“…The DW velocity calculated using S is found to be systematically lower. Here we choose to be conservative instead of trying to compensate for this discrepancy, as finite thermal activation is expected to increase the DW velocity by reducing the DW friction [11,28,40], as is the case for long pulses. So far, little study has been spent on such an issue in the flow regime of the CIDWM, although the absolute magnitude of enhancement was once shown to be 20 % for a SAF [41] for 40 K of temperature increase.…”