Effect of Annealing on the Temperature Dependence of the Effective Susceptibility Exponent of an Amorphous Ferromagnet

Scaling behaviour of magnetization for temperatures in the vicinity of, and far from, the ferromagnetic - paramagnetic phase transition in amorphous and alloys

“…Consistent with this variation of β eff ( ) and γ eff ( ), the sign of the CTS amplitudes (positive for a − M 2 and negative for a − M 1 , a + χ 1 and a + χ 2 , tables 3 and 4) in the present case is exactly opposite to that previously found in the ferromagnetic systems mentioned above. However, the overall behaviour of γ eff ( ) in a larger temperature range, i.e., from T C to T max (the maximum temperature covered in the present experiments), shown in figure 16, for the present alloys is similar to that observed earlier in a number of disordered systems [22,23,26,27,32,33]. The continuous curves in figure 16 represent the CTS fits to the γ eff ( ) data based on (21) in the ACR, as described above.…”

“…These results find a straightforward but qualitative explanation [4,22,23,26,32] in terms of the infinite ferromagnetic (FM) matrix plus finite FM spin clusters model (the details of this model are given in our earlier reports [4,26,43]), as is evident from the remarks made below. Within the framework of this model, even at low temperatures (T T C ), the ferromagnetic coupling between the spins that constitute the finite clusters is much stronger than that between the spins of the FM matrix.…”

“…A cursory glance at the MAPs depicted in figures 3 and 9 suffices to reveal that the slope of the MAP isotherms decreases continuously with increasing temperature. This feature of MAP is characteristic [4,5,22,23,26,27,32,33,36,37] of both crystalline and amorphous ferromagnets. The Arrott-Noakes equation of state in linear variables and H (i.e., ( 6)) cannot account for this variation in the slope of MAP isotherms since the coefficients a and b in (6) are temperature independent.…”

Asymptotic critical behaviour of quenched random-exchange Heisenberg ferromagnets

“…are not true asymptotic values, and that a reanalysis, which gives due consideration to the confluent singularity terms, of tbe bulk magnetization data already available [ 13,14,17,22] on some compositions in the glassy alloy series a-FeXNiso-,Bl9Sil is called for. However, inclusion of the CTS terms in the data analysis demands a far greater precision in the measurements than achieved hitherto.…”

“…This realization prompted us to undertake highprecision magnetization measurements on the amorphous alloys with x = 10, 13, and 16 in the above-mentioned series and on a-FezoNisoBlo. Moreover, we have taken new sets of AC ('zero-field') susceptibility, xo(T), data on samples (with composition x = 10, 13 and 16) the same as those used in our recent resistivity, p ( T ) , measurements [30] and then performed magnetization, M ( H , T), measurements on them with a view to test the validity of the claim recently made by Giintzel and Westerholt [28] that the low-field AC susceptibility is not well suited to study critical behaviour in metallic glasses and to investigate in depth the possible bearing of deviations from the straight-line Arrott plot isotherms observed [ 13,14,22,24,28] at low fields, usually encountered in amorphous ferromagnets, on the critical behaviour. The fact that all three physical quantities, i.e.…”