Thickness Dependence of the Dzyaloshinskii-Moriya Interaction in Co2FeAl Ultrathin Films: Effects of Annealing Temperature and Heavy-Metal Material

Abstract

The interfacial Dzyaloshinskii-Moriya interaction (iDMI) has been investigated in Co 2 FeAl (CFA) ultrathin films of various thicknesses (0.8 nm≤t CFA ≤2 nm) grown by sputtering on Si substrates, using Pt, W, Ir and MgO buffer or/and capping layers. Vibrating sample magnetometry (VSM) revealed that magnetization at saturation (M s ) for the Pt and Ir buffered films is higher than the usual M s of CFA due to the proximity induced magnetization (PIM) in Ir and Pt, estimated to be 19% and 27%, respectively. The presence of PIM in these materials is confirmed using x-ray resonant magnetic reflectivity. Moreover, while no PIM is induced in W, higher PIM is obtained with Pt when it is used as buffer layer rather than capping layer. Brillouin light scattering (BLS) in the Damon-Eshbach geometry has been used to investigate the thickness dependencies of iDMI constants, from the spin waves non-reciprocity, and the perpendicular anisotropy field versus the annealing temperature. The DMI sign has been found to be negative for Pt/CFA and Ir/CFA while it is positive for W/CFA. The thickness dependence of the effective iDMI constant for stacks involving Pt and W shows the existence of two regimes similarly to that

Robust Formation of Ultrasmall Room-Temperature Neél Skyrmions in Amorphous Ferrimagnets from Atomistic Simulations

“…Their isotropic structure helps with avoiding defect pinning 18 , while their intrinsic perpendicular magnetic anisotropy (PMA) 32–35 helps stabilize small skyrmions by allowing the use of thicker films (>5 nm). However, the effectiveness of interfacial DMI decreases significantly away from the interface 28–31 , which is the focus of our present investigation. Besides PMA, the magnetization of RE-TM alloys vanishes at the compensation temperature 36 .…”

“…Thicker magnetic layers are required in most cases to increase stability 17,18 . However, for ferromagnet (FM)/heavy metal multilayer stacks, increase in thickness of the magnetic layer can lead to a loss of interfacial anisotropy and the reduction of the strength of average DMI 28–31 , both of which are critical for skyrmion formation. To overcome these challenges, we need to consider a suite of materials and understand their underlying physics, especially with varying film thickness.…”

Spin‐Dependent Thermoelectric Transport in Cobalt‐Based Heusler Alloys

“…[129] Moreover, the interfacial Dzyaloshinskii-Moriya interaction (iDMI) was investigated in CFA ultrathin films of various thicknesses and with various buffer layers by measuring spin waves with Brillouin light scattering (BLS). [130,131] And the current-induced dipolar magnetic skyrmions in Co-based Heusler alloy CFA at room temperature have been reported by Husain et al [132] and Akhtar et al [133] Although they did not observe a clear skyrmion Hall effect [134] in this system due to the pinning effects, it is still very promising to explore the efficient skyrmion motion in Heusler alloys where the stabilization of magnetic skyrmions under ambient conditions is possible.…”

“…[ 129 ] Moreover, the interfacial Dzyaloshinskii–Moriya interaction (iDMI) was investigated in CFA ultrathin films of various thicknesses and with various buffer layers by measuring spin waves with Brillouin light scattering (BLS). [ 130,131 ] And the current‐induced dipolar magnetic skyrmions in Co‐based Heusler alloy CFA at room temperature have been reported by Husain et al. [ 132 ] and Akhtar et al.…”

Interface phenomena in ferromagnet/ TaOx -based systems: Damping, perpendicular magnetic anisotropy, and Dzyaloshinskii-Moriya interaction

“…3. For samples where the MS-FMR signal is not enough to be detected, BLS measurements were used to determine M eff as described in [30]. Positive values of M eff correspond to in-plane spontaneously magnetized films (IPM) while negative values refer to out-of-plane spontaneously magnetized samples (OPM).…”