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Magnetic dynamic damping is significantly important in determining the relaxation time of magnetic moments and the speed of magnetic memory devices. Here, magnetic dynamic behaviors of permalloy (Py) films capped with gadolinium (Gd) are studied, and the effects of the interface are investigated by the Cu insert layer. For Py/Gd bilayer films, both the saturation magnetization ( ${M}_{s}$ ) and the surface anisotropy constant ( ${K}_{{\bot }}$ ) are decreased with increasing Gd thickness, while the Gilbert damping ( $\alpha$ ) is enhanced. With the insert of Cu at Py/Gd interface, the above tendencies of ${M}_{s}$ , ${K}_{\bot }$ , and $\alpha $ are suppressed. We attribute these phenomena to the antiferromagnetic coupling between Gd and Py near the interface, which are caused by the magnetic proximity effect (MPE) instead of the spin relaxation in the rare earth Gd themselves.

We investigate the current induced depinning of magnetic domain walls (DWs) trapped at the kinks in a patterned Py nanowire with two-kink zigzag shape on Si/SiO2 substrate. By injecting pulse current with varying amplitude, two threshold current densities with a slight difference of around $6 \times 10^{10}$ A m−2 have been determined according to the different depinning process. The smaller threshold current density corresponds to the depinning of a single DW which is always the first DW facing to the electron flow. This fact indicates that the different pinning potential caused by the structural asymmetry is not the key to determine which DW is to depin. Micromagnetic simulations provide evidence that the specific current-driven behavior of the vortex DW might account for the single depinning process. The larger threshold corresponds to the simultaneous depinning of two DWs which has been commonly observed in a variety of shaped nanowires. This asynchronous depinning phenomenon provides the possibility of the selective DW depinning in the future logic devices.

The Tb(4 nm)/Cr( ${t}$ nm)/Fe(5 nm) trilayers with different thicknesses of Cr layer have been investigated by X-ray diffraction, vibrating sample magnetometer, and ferromagnetic resonance. When Cr is thinner than 1.8 nm, the ferromagnetic coupling of Tb and Fe leads to higher saturation magnetization ( $M_{s}$ ) than that of Fe(5 nm) film. On the other hand, the Gilbert damping constant $\alpha $ in all the trilayers have been found to exceed the magnitude of the Fe. In particular, when Cr layer is 1 nm thick, $\alpha $ increases by 38% and $M_{s}$ is increased by 6%; when Cr layer is 4 nm thick, $\alpha $ is increased by 46%, while $M_{s}$ is only decreased by 5%. Accordingly, we have demonstrated a way for enhancing damping and magnetic moment simultaneously in the Tb(4 nm)/Cr( ${t}$ nm)/Fe(5 nm) trilayers.

Single-crystal Fe dot arrays with the lateral size varying from 400 nm to 50 nm are fabricated by focused ion beam (FIB) direct writing from a single-crystalline 10 monolayer (ML) Fe (100) continuous thin film grown on GaAs substrate. The Kerr hysteresis loops of both dot arrays and continuous thin film are measured by focused magnetooptical Kerr effect (MOKE) measurements along four major crystal directions: [0-11] [010] [011] and [001]. It is found that the in-plane uniaxial anisotropy has been greatly reduced down to zero in the dot arrays when the size is less than 150 nm. The micromagnetic simulations confirm the reduction of this intrinsic in-plane uniaxial anisotropy in the patterned dots by separating the effect of the shape anisotropy. The experimental and simulation results further indicate an additional magnetic uniaxial anisotropy along the [010] direction.

Magnetic anisotropies of Fe/MgO/GaAs(100) hybrid structure with two different nonmagnetic capping materials, Au and MgO have been studied by ferromagnetic resonance (FMR). A uniaxial anisotropy, unexpected from the crystal structure was observed in the ultrathin films for both capping materials. Its global easy axis is along [0-11] direction while two (010) directions are equally magnetic hard regardless of the overlayer material. The in-plane uniaxial anisotropy (in-plane cubic anisotropy) of the Au capped samples is stronger (weaker) than that of the MgO capped ones within the range of t Fe = 7.1 to 28 ML. This suggests that the MgO overlayer suppresses the uniaxial anisotropy faster than the Au overlayer.