Thermal and spontaneous remagnetization in the bulk amorphous ferromagnets Nd60Fe30Al10 and Nd60Fe20Co10Al10

Abstract

Bulk amorphous Nd60Fe30Al10 and Nd60Fe20Co10Al10 alloys, which display hard magnetic properties, have been prepared by arc melting and quenching into a copper mould. Following magnetic saturation and dc demagnetization, at room temperature, both materials are seen to exhibit the phenomena of thermal and spontaneous remagnetizations. The behavior of the observed thermal and spontaneous remagnetizations is similar to that exhibited in nucleation controlled sintered permanent magnets. The thermal remagnetization data are fitted using a model, developed from the theory of Schumann and Jahn [J. Magn. Magn. Mater. 232, 231 (2001)] for explaining thermal remagnetization in polycrystalline magnets, to gauge its usefulness when applied to amorphous ferromagnets. The spontaneous remagnetization behavior is interpreted in the context of the Preisach model.

Magnetic and anomalous magnetic viscosity in the bulk amorphous ferromagnet and partially amorphous ferromagnet

“…(3) yields for amorphous Pr 58 Fe 24 Al 18 values for v a and the activation diameter, D a , of 6:9 Â 10 À18 cm 3 and 23.6 nm, respectively. This is in accord with values for v a and D a of 4 Â 10 À18 cm 3 and 19.7 nm, respectively, for Nd 60 Fe 20 Co 10 Al 10 [8], and with values for v a and D a of 2:6 Â 10 À18 cm 3 and 17.1 nm, respectively, for Nd 60 Fe 30 Al 10 (deduced from data in [6,19]). Billoni et al [20] in a study of Nd 60 Fe 30 Al 10 bulk amorphous ferromagnets have used a similar approach, and obtain an activation length of 10-20 nm, which is in good agreement with our results.…”

“…The amorphous Pr 58 Fe 24 Al 18 alloy attains a value, after recoiling to 294 K, of 11.4% of its value at remanence. This is similar to Nd 60 Fe 30 Al 10 and Nd 60 Fe 20 Co 10 Al 10 bulk amorphous ferromagnets, where values of 12.6% and 9.4% of remanence, respectively, are obtained [19]. In bulk amorphous ferromagnets thermal remagnetisation is about four times larger than spontaneous remagnetisation.…”

“…For comparison, included in Fig. 9, are data for Nd 60 Fe 30 Al 10 and Nd 60 Fe 20 Co 10 Al 10 from our earlier studies of these materials [19,27]. Spontaneous remagnetisation is a small effect, attaining a value of % 5% of remanence after 25,000 s in both the amorphous and partially amorphous Pr-Fe-Al alloys.…”

“…The model is closely related to the Preisach model, but differs in that the magnetic field near a grain is subject to fluctuations (a statistically fluctuating interaction field) from nearby grains [34]. The model has been applied with limited success to bulk amorphous alloys [19].…”

Structural and Magnetic Properties of Ho₃Fe_29-x<i>T</i>_x (<i>T</i>=V and Cr) Compounds

“…In order to find noninterstitial 3:29-type compounds which exhibit uniaxial anisotropy at room temperature, it is necessary to study the effects of substitution of other magnetic or nonmagnetic elements for Fe or R in R 3 (Fe, T) 29 compounds. Up to now, a series of single-phase R 3 (Fe,T) 29 compounds with R=Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy and T=Ti, V, Cr, Mn, Nb, Mo, W, and Re have been synthesized [6][7][8][9][10][11][12][13][14][15][16][17][18], nevertheless the study of 3:29 phase R-T intermetallics with R being the heavy rare-earth elements was rarely reported due to the difficult synthesis. In this letter, on the basis of our previous work on Ho 3 (Fe,T) 29 (T=V and Cr) compounds [19], a study of crystallographic structure by Rietveld refinement analysis of XRD pattern as well as magnetic properties of the Ho-Fe-V/Cr compounds was presented.…”