Determination of the magnetization scaling exponent for single-crystal by broadband microwave surface impedance measurements

Abstract

Employing a broadband microwave reflection configuration, we have measured the complex surface impedance, (Formula presented) of single-crystal (Formula presented) as a function of frequency (Formula presented) and temperature (Formula presented) Through the dependence of the microwave surface impedance on the magnetic permeability, (Formula presented) we have studied the local magnetic behavior of this material, and have extracted the spontaneous magnetization, (Formula presented) in zero applied field. The broadband nature of these measurements and the fact that no external field is applied to the material provide a unique opportunity to analyze the critical behavior of the spontaneous magnetization at temperatures very close to the ferromagnetic phase transition. We find a Curie temperature (Formula presented) and scaling exponent (Formula presented) in agreement with the prediction of mean-field theory. We also discuss other recent determinations of the magnetization critical exponent in this and similar materials and show why our results are more definitive. © 2000 The American Physical Society.