Limiting Velocity and Dispersion Law of Domain Walls in Ferrimagnets Close to the Spin Compensation Point

JETP Letters - The motion of domain walls in GdFeCo-type ferrimagnets near the point of compensation of sublattice spins s1 and s2, when the effects of the exchange increase in the limiting wall...     

The temperature dependence of the symmetric exchange interaction by optical phonon modulation of the exchange integral

By assuming an anharmonic intermolecular potential for lattice displacement and an exponential form for the exchange energy, the exchange interaction is shown to be temperature dependent in the paramagnetic region. Bond strengths are taken from known tabulated results and overlap integrals are calculated with Slater-type orbitals so there are no adjustable parameters. Agreement with experimental results on K₂CuCl₄ · 2H₂O and other layered compounds is shown.     

Non-Newtonian dynamics of the fast motion of a magnetic vortex

The dynamics of a magnetic vortex in a thin magnetically soft ferromagnetic disc with a submicron diameter has been analyzed. Under the action of field pulses with a duration of the order of 10–100 ps, the vortex undergoes a complex motion. The analysis of the results of a micromagnetic simulation indicates that this motion is non-Newtonian. It can be described by an equation containing the third time derivative of the displacement of the vortex core.     

Fine structure of the spectra of magnetic particles in the vortex state and their ordered arrays

A low-frequency (the frequency ω_VPM is in the sub-GHz range) mode exist for submicron magnetic particles in the vortex state. This mode corresponds to oscillations of the vortex center. The other modes form doublets with higher (several gigahertz) frequency and small (about ω_VPM) splitting. Collective oscillations exist for lattices of such particles. The dependence of the frequency of these modes on the quasi-momentum can be nonanalytic.     

Green's function theory for the one-dimensional antiferromagnet with antisymmetric exchange

The spin wave spectrum for the one-dimensional antiferromagnet with antisymmetric exchange is obtained from second order Green's function theory. There is a noticeable asymmetry in the spin wave dispersion curve, which has an effect on the static correlation function and the correlation length.     

High frequency modes in vortex-state nanomagnets

The magnon mode excitation spectrum is obtained from a linearized set of Landau-Lifshitz equations for vortex ground state cylindrical nanomagnets in an external magnetic field. It is shown that there is a rich spectrum of doublet states, and the splitting can be amplified in an external magnetic field.     

Excitation of spin dynamics by spin-polarized current in vortex state magnetic disks

A spin-polarized current with the polarization direction perpendicular to a disk in the vortex ground state will result in renormalization of the effective damping of excitations on this state. As the current is increased to a threshold current Ic the effective damping will be zero and the lowest threshold current corresponds to the vortex gyrotropic mode. For larger values of the current the excitation is a nonlinear gyrotropic mode having nonsmall amplitudes and larger frequency than the linear mode. This effect occurs for any mode of the vortex-state disk, and the value of Ic is proportional to the mode frequency.     

An exact partition function for the classical Dzialoshinsky-Moriya chain

The exact partition function for the classical anisotropic chain with antisymmetric exchange is evaluated. For certain values of parameters in the hamiltonian, it is seen that the partition function is the same as the classical isotropic chain partition function.