Chiral domain wall motion in unit-cell thick perpendicularly magnetized Heusler films prepared by chemical templating

Abstract

Heusler alloys are a large family of compounds with complex and tunable magnetic properties, intimately connected to the atomic scale ordering of their constituent elements. We show that using a chemical templating technique of atomically ordered X′Z′ (X′ = Co; Z′ = Al, Ga, Ge, Sn) underlayers, we can achieve near bulk-like magnetic properties in tetragonally distorted Heusler films, even at room temperature. Excellent perpendicular magnetic anisotropy is found in ferrimagnetic X3Z (X = Mn; Z = Ge, Sn, Sb) films, just 1 or 2 unit-cells thick. Racetracks formed from these films sustain current-induced domain wall motion with velocities of more than 120 m s−1, at current densities up to six times lower than conventional ferromagnetic materials. We find evidence for a significant bulk chiral Dzyaloshinskii–Moriya exchange interaction, whose field strength can be systematically tuned by an order of magnitude. Our work is an important step towards practical applications of Heusler compounds for spintronic technologies.

Nanoscale Noncollinear Spin Textures in Thin Films of a D2d Heusler Compound

“…[ 14 ] One method that has been shown to give rise to chemical ordering at temperatures as low as even room temperature for binary Heusler compounds is the chemical templating (CTL) method. [ 29 ] It is of great interest to explore this method in the future and see whether it can be extended to ternary Heuslers. If one can prepare ultrathin D 2d Heusler films, the current driven motion of noncollinear nanoscale objects in such films driven by spin–orbit torques can be explored by combining these films with layers in which there is significant charge to spin conversion.…”

Spintronic devices: a promising alternative to CMOS devices

“…This vertical arrangement is considered as a breakthrough, where a forest of such nanowires is arranged, which tremendously increases the storage capacity in RM. Such an arrangement of RM with large data storage capacity and minimum footprint is advocated to replace the current memory structures at different levels such as SRAM and DRAM cache [220,[227][228][229][230][231][232], GPU register [233][234][235], and off-chip (stand-alone) memory [236] owing to its non-volatility, high read/write speed, and lower read/write energy. Diligent efforts needed to investigate the feasibility of replacing the main memory by RM.…”

Magnetic Racetrack Memory: From Physics to the Cusp of Applications Within a Decade

“…Recent material developments and techniques have allowed for the exploration of RTM on high-quality epitaxial ferrimagnetic oxides [76], [77] and Heusler compounds with a wide range of fascinating properties. The latter were shown to grow in ultrathin form on technologically relevant silicon substrates using novel chemical templating layers (CTL) [78].…”

“…Another epitaxial system-Heusler materials and compounds-has shown efficient chiral DW motion in their ultrathin form, with growth at room temperature [78]. A CTL method allows even single unit cell thick layers of the low moment ferrimagnetic binary Heusler alloys, Mn 3 Z, where Z = Ge, Sn, Sb, to be grown on amorphous underlayers.…”

“…The result of the STT on the chiral Néel DWs creates a damping torque that acts on the magnetic moments of the DW, causing thereby a precessional motion and the DW motion along the electron spin polarization direction. The spin current from the CTL layer (or adjacent nonmagnetic overlayers [78]), owing to the DMI, and the damping torque results in a torque that is always out of the plane of the racetrack layers. The direction of this torque depends on the handedness of the chirality and the spin accumulation of the material-dependent CTL.…”