Magnetic behavior of melt-spun gadolinium

Authors

P. M. Shand, University of Northern IowaFollow
J. G. Bohnet, University of Northern Iowa
Jeffrey E. Shield, University of Nebraska - LincolnFollow
D. Schmitter, University of Nebraska - Lincoln
G. Shelburne, University of Nebraska - Lincoln
Diandra Leslie-Pelecky, University of Nebraska -- LincolnFollow

Date of this Version

5-14-2008

Comments

Published by American Physical Society. Phys. Rev. B. 77, 184415 2008. http://prb.aps.org. Copyright © 2008 American Physical Society. Permission to use.

Abstract

Melt-spun Gd is a structurally inhomogeneous system consisting of crystalline grains with an average size of 24±3 nm that are separated by an amorphous interphase. This system exhibits a depression of T_C (289.70±0.01 K) relative to bulk Gd (293 K). The effective critical exponents (β_eff=0.389±0.017, γ_eff =1.300±0.014, and δ =4.32±0.02) and critical amplitudes indicate that for the reduced-temperature range in this work, the paramagnetic-to-ferromagnetic transition is consistent with the isotropic dipolar universality class shown by bulk Gd. There is, however, evidence of enhanced anisotropy in the critical behavior of ms-Gd. Increasing random anisotropy in the intergrain regions with decreasing temperature below T_C diminishes the coupling between the ferromagnetically ordered grains and produces a previously unobserved low-temperature peak in the imaginary part of the ac susceptibility. The random-anisotropy model provides a good description of the approach to saturation, which may result from the ferromagnetic correlation length becoming comparable to the anisotropy correlation length in the strong-field regime of the model.