Wei Tang

Enhanced giant magnetoresistance in Ni-doped antipervoskite compounds GaCMn3−xNix(x=0.05,0.10)

We report an enhanced negative giant magnetoresistance (GMR) with larger temperature span in Ni-doped antipervoskite compounds GaCMn3−xNix. The observed GMR can peak at ∼75% (at 85 kOe) and exceed 60% (at 50 kOe) over a temperature span of approximate 110 and 50K for x=0.05 and 0.10, respectively. Compared with the parent GaCMn3, the well-enhanced GMR in Ni-doped samples is suggested to be associated with the partially suppressed antiferromagnetic (AFM) ground state, which favors the transition from the high-resistivity AFM state to the low-resistivity canted ferromagnetic state under an external magnetic field.

Spin-wave propagation in domain wall magnonic crystal

We present a new type of magnonic crystal consisting of a series of periodically distributed magnetic domain walls in a uniform strip. When spin waves propagate in such a structure, allowed and forbidden bands are formed due to translation symmetry and scattering of the spin waves at the domain wall boundaries caused by the dynamic stray field in the domain wall region. The control of the bandgap position in frequency and its width by the period of magnonic crystal and the domain wall width is investigated. It is found that the bandgap position decreases monotonously with the increase of the period or domain wall width, while the bandgap width displays an oscillated behavior. The origin of the oscillation of the bandgap width is discussed. This work may provide a new way of designing reconfigurable magnonic devices.

Steady-state domain wall motion driven by adiabatic spin-transfer torque with assistance of microwave field

We have studied the current-induced displacement of a 180° Bloch wall by means of micromagnetic simulation and analytical approach. It is found that the adiabatic spin-transfer torque can sustain a steady-state domain wall (DW) motion in the direction opposite to that of the electron flow without Walker Breakdown when a transverse microwave field is applied. This kind of motion is very sensitive to the microwave frequency and can be resonantly enhanced by exciting the domain wall thickness oscillation mode. A one-dimensional analytical model was established to account for the microwave-assisted wall motion. These findings may be helpful for reducing the critical spin-polarized current density and designing DW-based spintronic devices.

Spin waves in the soft layer of exchange-coupled soft/hard bilayers

The magnetic dynamical properties of the soft layer in exchange-coupled soft/hard bilayers have been investigated numerically using a one-dimensional atomic chain model. The frequencies and spatial profiles of spin wave eigenmodes are calculated during the magnetization reversal process of the soft layer. The spin wave modes exhibit a spatially modulated amplitude, which is especially evident for high-order modes. A dynamic pinning effect of surface magnetic moment is observed. The spin wave eigenfrequency decreases linearly with the increase of the magnetic field in the uniformly magnetized state and increases nonlinearly with field when spiral magnetization configuration is formed in the soft layer.

Spin wave modes of width modulated Ni80Fe20/Pt nanostrip detected by spin-orbit torque induced ferromagnetic resonance

We study magnetic dynamics of Ni80Fe20/Pt magnonic crystals made of width periodically varied nanostrips using the spin-torque induced ferromagnetic resonance technique. DC voltage signals are detected when nanostrip magnonic crystals (MCs) are driven resonantly. The DC voltage originates dominantly from the spin rectification effect due to the coupling between the AC electrical current and the oscillated anisotropic magnetoresistance. In addition to uniform magnetization precession across the MC, localized spin wave modes are also observed. Their evolution with the strength and direction of the magnetic field are studied. Micromagnetic simulations are performed to illustrate the experimental results.We study magnetic dynamics of Ni80Fe20/Pt magnonic crystals made of width periodically varied nanostrips using the spin-torque induced ferromagnetic resonance technique. DC voltage signals are detected when nanostrip magnonic crystals (MCs) are driven resonantly. The DC voltage originates dominantly from the spin rectification effect due to the coupling between the AC electrical current and the oscillated anisotropic magnetoresistance. In addition to uniform magnetization precession across the MC, localized spin wave modes are also observed. Their evolution with the strength and direction of the magnetic field are studied. Micromagnetic simulations are performed to illustrate the experimental results.