Kaul, S. N. ; Mohan, Ch. V. (1992) Effect of isothermal annealing on the magnetic behavior of amorphous ferromagnets with composition near the percolation threshold. I. Outside the critical region Journal of Applied Physics, 71 (12). pp. 6090-6102. ISSN 0021-8979
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Official URL: http://jap.aip.org/resource/1/japiau/v71/i12/p6090...
Related URL: http://dx.doi.org/10.1063/1.350416
Abstract
Results of detailed ferromagnetic resonance measurements taken on amorphous (a-) Fe90+XZr10-X alloys with X=0 and 1 in the horizontal-parallel and vertical-parallel sample configurations at a fixed microwave frequency of =9.23 GHz in the temperature range 77 to 300 K before and after these alloys have undergone isothermal annealing treatment at 400 K for durations of time, tA, ranging from 10 to 240 min are presented and discussed. While only a single (primary) resonance is observed for T≤ TC (the Curie temperature), an additional (secondary) resonance first appears at T= TC and then gets fully resolved for T≥ (TC+10 K). For the primary resonance (i) the "in-plane" uniaxial anisotropy field, Hk, and the Gilbert damping parameter, λ, both scale with the saturation magnetization, MS, in the temperature ranges 77 K≤ T≤ TC and 0.5TC≤ T≤ 0.8TC, respectively, at all tA including tA=0; (ii) isothermal annealing has essentially no effect on MS(T), the "peak-to-peak" linewidth, Δ Hpp(T), Δ H0 (the frequency- and temperature-independent contribution to Δ Hpp) and λ (T); (iii) with increasing Fe concentration, the value corresponding to the peak in λ (T) decreases, λ (0.5TC) increases while λ (300 K) stays constant at 1×108 s-1, and (iv) isothermal annealing up to a time duration of 30 min results in an enhancement of about 1.5% in TC and a reduction of nearly 40% in the characteristic temperature T0 (which is a measure of the re-entrant transition temperature) whereas no further change occur- s in both TC and T0 at higher annealing times. By contrast, for the secondary resonance, (a) Hk=0 at all temperatures T≥TC and values of tA covered in the present experiments, (b) isothermal annealing leaves the resonance field unaltered, and (c) a steep decline in the value of Δ Hpp' occurs for tA≤ 10 min but at higher values of tA, Δ Hpp' remains constant for a-Fe90Zr10 whereas it increases at first and then saturates in the case of a-Fe91Zr9. The effect of isothermal annealing on the quantities of interest, i.e., TC, T0, Δ Hpp, etc., can be qualitatively understood in terms of a finite spin clusters plus an infinite ferromagnetic matrix model.
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ID Code: | 29780 |
Deposited On: | 23 Dec 2010 04:47 |
Last Modified: | 07 Jun 2011 04:35 |
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