Modified mean-field model for rare-earth–iron amorphous alloys

Abstract

A mean-field model of the magnetic properties of amorphous rare-earth–iron alloys has been developed which incorporates an Fe spin whose dependence on both the concentration and the species of rare earth is based on Mössbauer spectra. Using this model with a single fixed set of exchange constants, we have been able to calculate Curie temperatures which are in reasonable agreement with the data for amorphous rare-earth (Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu–iron alloys containing between 50 and 100 at.% iron. Better agreement with the measured Curie temperatures is achieved if the magnitudes of the Fe-Fe and rare-earth–Fe exchange constants are allowed to increase linearly with rare-earth concentration. The latter case has the additional advantage of reproducing the observed shape of the magnetization-vs-temperature curves for wide range of composition and rare-earth species.

Ferrimagnetic Tb–Fe Alloy Thin Films: Composition and Thickness Dependence of Magnetic Properties and All-Optical Switching

“…This increase can be attributed to a more collinear alignment (compression) of the distributed magnetic moments of Tb along the external field direction. In contrast, for Fe rich Tb-Fe films where the Fe moment is dominating, no pronounced magnetic field dependent increase of the magnetization was observed due to the stronger TM-TM exchange coupling of Fe (Heiman, 1976). Please note that this approach does not allow determining the exact fanning cone angle of the Tb moments, as the Tb fanning cannot be fully compressed and the Fe cone will certainly expand at the same time, thus these results should be treated with care and serve only as a first indicator.…”

Thermal stability and magnetic properties of partially Co-substituted (Fe71.2B24Y4.8)96Nb4 bulk metallic glasses

“…The exchange stiffness constant, A, can be obtained from the mean field model and from the Curie temperature. [31][32][33] If one assumes Hasegawa's model 31 Co, the magnetic saturation should be considered as: The magnetic properties are typical for soft magnetic materials. The Curie temperature increases upon Co addition and the saturation magnetization decreases, but first goes through a maximum for x = 0.1.…”

Calculations of Bulk-Like Transition Temperatures of Rare Earth-Transition Metal Alloys AcB1-c Using the Effective Field Theory

“…One of the earliest studies concerning the properties of these alloys is that of Heiman et al [19]. In this work one finds some data, for example, for T C and T comp versus the concentration c for both the crystalline and amorphous phases of Fe c Gd 1--c .…”

“…[20] in order to compare the theoretical results, even though the data are collected from different references and therefore from different samples, and the data are given especially for the amorphous phase. Heiman et al [19] do not indicate that the data may be different for the crystalline and the amorphous phase but this is given for a very limited range of c. It is important to note that there is no overall agreement from one study to another concerning the values of the exchange integral constants.…”