Search

It is shown that surface domain structure arises in magnetic nanotube with uniaxial anisotropy if surface anisotropy constant is negative and sufficiently high in absolute value. The surface magnetic anisotropy affects also the structure and dynamics of a head-to-head domain wall propagating along the nanotube axis in applied magnetic field. The hopping mode is observed for stationary movement of a head-to-head domain wall. The average speed of the domain wall in the hopping mode is found to be several times less than the stationary velocity of the wall in the absence of surface anisotropy. This effect is important for various applications where fast propagation of the domain wall along the sample is essential.

Cosmos-1809 satellite data on ELF emissions, plasma density, Ne and variations dNe in the ionosphere above the Spitak earthquake zone during a period of enhanced aftershock activity are presented. The data show that small-scale plasma inhomogeneities with d N e N e ≈ 3–8% and with a characteristic scale of 4–10 km along the orbit are excited on geomagnetic field tubes connected to the epicentral region, simultaneously with earthquake related ELF emissions. A generation mechanism for such inhomogeneities under the influence of seismic activity in terms of the dissipative instability of acoustic-gravity waves in the ionosphere is proposed.