DIFFERENTIAL SUSCEPTIBILITY, STRUCTURE CONSTANT AND LOSSES IN NI-FE THIN-FILMS

An investigation was made of the transverse susceptibility of thin NiFe films prepared under ultrahigh vacuum conditions. Both a.c. and d.c. field amplitude dependences of the transverse susceptibility were measured and the conditions for resonance were studied. Two types of a.c. field dependences were found. At low d.c. bias fields the susceptibility was found to increase linearly with the a.c. measuring field at small a.c. field amplitudes. Both the real and imaginary parts of the susceptibility were non-trivial when extrapolated to zero a.c. field. At higher values of the d.c. field the susceptibility was found to be independent of the a.c. field. For resonance measurements resonance peaks at 50 and 200 MHz were observed. These results are discussed in terms of two types of loss mechanism. One of the mechanisms was identified as the irreversible rearrangement of domain or ripple walls. The other mechanism is postulated to be magnetic damping of ripple movement. The initial differential susceptibility was obtained by extrapolating the measured susceptibility values to zero a.c. field and was analysed using existing micromagnetic theory. Good agreement was obtained for low dispersion films but not for high dispersion films. © 1979.