The microscopic origin of DMI in magnetic bilayers and prediction of giant DMI in new bilayers

Abstract

Skyrmions are widely regarded as promising candidates for emergent spintronic devices. Dzyaloshinskii–Moriya interaction (DMI) is often critical to the generation and manipulation of skyrmions. However, there is a fundamental lack of understanding of the origin of DMI or the mechanism by which DMI generates skyrmions in magnetic bilayers. Very little is known of the material parameters that determine the value of DMI. This knowledge is vital for rational design of skyrmion materials and further development of skyrmion technology. To address this important problem, we investigate DMI in magnetic bilayers using first principles. We present a new theoretical model that explains the microscopic origin of DMI in magnetic bilayers. We demonstrate that DMI depends on two parameters, interfacial hybridization and orbital contributions of the heavy metal. Using these parameters, we explain the trend of DMI observed. We also report four new materials systems with giant DMI and new designs for magnetic multilayers that are expected to outperform the best materials known so far. Our results present a notably new understanding of DMI, uncover highly promising materials and put forth pathways for the controlled generation of skyrmions.

Dynamic Symmetry Breaking in Chiral Magnetic Systems

“…The number of [Co/Ni/Pt] repetitions N was varied between 1 and 5. The authors’ choice of materials was motivated by reports that Pt/Co and Pt/Ni interfaces were predicted to have different signs of iDMI, [ 39 ] such that an additive iDMI may be achieved when they were incorporated in a structurally asymmetric Pt/Co/Ni/Pt heterostructure. [ 40 ]…”

Variation of sign and magnitude of the Dzyaloshinskii-Moriya interaction of a ferromagnet with an oxide interface

“…WXY Z[\ is very small and positive for the control sample [region (d)]. The small value of 9:; RST , is in accordance with the fact the interfacial DMI is usually small for early 5d elements like Hf and Ta due to their small SOC[41].9:; RST , increases, accompanied by a sign reversal after oxidizing the CoFe surface [region (a) and (b)]. We furthermore observed a minimum in 9:; RST , at the transition from region (b) to (c)until it stabilizes at above dTa = 1 nm.…”

Visibility and Apparent Size of Néel-Type Magnetic Skyrmions in Fresnel Defocus Images of Multilayer Films

“…The Pt/Co interfaces are expected to provide a large magnetic anisotropy perpendicular to the layers and host a large positive DMI. (Values of +1.5-+3 meV have been reported (Yang et al, 2015;Boulle et al, 2016;Jadaun et al, 2020).) On the other hand, the Pt/Py interface should host a negative DMI.…”

“…On the other hand, the Pt/Py interface should host a negative DMI. (Values of approximately −1 meV have been reported for Pt/Py (Nembach et al, 2015) and Pt/Ni interfaces (Chen et al, 2013;Jadaun et al, 2020).) The stack was deposited directly onto a 15-nm-thick SiN membrane using DC magnetron sputtering.…”