MAGNETOELASTIC AND TOTAL ANISOTROPY EFFECTS ON THE DOMAIN-WALL DYNAMICS IN THE POLYCRYSTALLINE STATE

This work investigates the domain-wall (DW) mobility due to magnetoela stic interaction. Polycrystalline samples with high grain-size homogen eity were prepared based on the general formula Y3Fe5-xMnxO12 (0 < x < 0.28). A series of samples was especially selected where the longitud inal magnetostriction changed from -2.14 X 10(-6) to + 7.65 X 10(-6) a t 300 K, while the single-crystal crystalline anisotropy constant K-1 remained negative. The effects of the magnetostriction and the total a nisotropy K on the complex magnetic permeability spectrum mu(f) were investigated in a broad frequency range (0.3-3 GHz). Two characteristi c regions of variation of the real (mu') and the imaginary (mu '') par ts of the complex permeability as functions of lambda(s) were establis hed. Near lambda(s) = 0, a resonance-type spectrum was observed. The m odel of 'diametrical spherical DW' is inapplicable for lambda(s) much greater than 0 - the DW dynamics is then influenced exclusively by the stress anisotropy and by the strong isotropic exchange stress arising from the anisotropic magnetostrictive deformation constrained by the neighboring grains. The significant decrease of the initial permeabili ty in this region can be explained by the rise in the concentration of DW not having a 180 degrees orientation.