Tuning Dzyaloshinskii-Moriya interaction in ferrimagnetic GdCo: A first-principles approach

Abstract

We present a systematic analysis of our ability to tune chiral Dzyaloshinskii-Moriya Interactions (DMI) in compensated ferrimagnetic Pt/GdCo/Pt1−xWx trilayers by cap layer composition. Using first principles calculations, we show that the DMI increases rapidly for only ∼ 10% W and saturates thereafter, in agreement with experiments. The calculated DMI shows a spread in values around the experimental mean, depending on the atomic configuration of the cap layer interface. The saturation is attributed to the vanishing of spin orbit coupling energy at the cap layer and the simultaneous constancy at the bottom interface. Additionally, we predict the DMI in Pt/GdCo/X (X = Ta, W, Ir) and find that W in the cap layer favors a higher DMI than Ta and Ir that can be attributed to the difference in d -band alignment around the Fermi level. Our results open up exciting combinatorial possibilities for controlling the DMI in ferrimagnets towards nucleating and manipulating ultrasmall high-speed skyrmions.

Interplay between Spin‐Orbit Torques and Dzyaloshinskii‐Moriya Interactions in Ferrimagnetic Amorphous Alloys

“…[48] The spins of CoGd layers were arranged in opposite chirality (clockwise and anticlockwise) and the total energy difference between the two configurations was taken to obtain the DMI strength as employed in previous studies. [49,50] Structural and computational details of these calculations are described in the recent paper by Morshed et al [46] For the calculations, two monolayers of Co x Gd 1-x (0.46 nm, x =75%) were used and the results were scaled to a 5-nm thick CoGd layer considering the DMI was an interfacial interaction and was inversely proportional to the thickness as experimentally demonstrated in CoGd films by Quessab et al [23] Statistical Analysis: Saturation magnetization values were obtained from magnetic hysteresis loops (VSM data) after linear subtraction of the paramagnetic contribution of the substrate. SOT phase diagrams were measured at least three times and the current-induced change of anomalous Hall resistance was normalized to the total change of anomalous Hall resistance induced by an out-of-plane magnetic field.…”

Tunable Magnetic Skyrmions in Ferrimagnetic Mn$_4$N

“…These calculations were generalized from the four-state energy mapping calculation of antisymmetric exchange interaction conducted by Xiang et al 49,50 . The validity of this method has been explored by several authors in different magnetic materials classes, including interfaces and bulk materials which gives confidence in applying these approaches in the current work 30,48,[51][52][53][54][55] . In general, the energy due to DMI can be written as 30,48,51,54,55 ,…”

“…The validity of this method has been explored by several authors in different magnetic materials classes, including interfaces and bulk materials which gives confidence in applying these approaches in the current work 30,48,[51][52][53][54][55] . In general, the energy due to DMI can be written as 30,48,51,54,55 ,…”

“…In this paper, we report the experimental observation of skyrmions in Mn 4 N thin films. In a recent study, tuning of interfacial DMI (iDMI) was reported in Pt/CoGd/Pt 1−x W x through the dilution of Pt with W in the capping layer 16,30 . Based on the simulated skyrmion phase diagram, such tuning of iDMI was predicted to allow the control of skyrmion size for desirable applications 31 .…”

“…In Mn 4 N, we have lighter, non-magnetic neighboring N-atoms that are in coordination with the magnetic Mn-atoms. More recently, Morshed et al reported a D µ between 0 and 4.5 mJ/m 2 in the Pt(2)/GdCo(2)/Pt 1−x W x (2) heterostructure, where (2) stands for the number of atomic layers in the simulation cell 30 . This comparison is also important because it shows that our DFT+U calculated D y µ for Pt/Mn 4 N(001) is larger than that of the Pt(2)/GdCo(2)/Pt 1−x W x (2) heterostructure.…”