Effect of magnetic field frequency on coercivity behavior of nanocrystalline Fe79Hf7B12Si2 glass-coated microwires

Dependence of coercitivy, H-c, on AC magnetic field frequency, f, has been studied in glass coated Fe79Hf7B12Si2 microwires exhibiting nanocrystalline structure. Annealing of the samples at 450-600 degrees C changes its structure and consequently the magnetic properties (coercivity and magneto stricti on constant). The grain size of the nanocrystals increases from about 17 nm up to 35 nm after annealing at 600 degrees C. For the as-prepared microwires the frequency dependence fits well to root f. In annealed at 550 degrees C samples H-c similar to f(2/3) dependenceis observed. In terms of the interpretation of the domain wall propagation, both kind of H-c(f) dependences can be interpreted considering depinned domain walls, i.e. neglecting elastic coefficient K of the domain wall motion equation. The H-c similar to root f corresponds better to low frequency limits while H-c similar to f(2/3) is attributed to the high frequency behavior. (c) 2007 Published by Elsevier B.V.