Critical behavior of the optical absorption edge in CdCr2Se4

I. Balberg*, A. Maman

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

18 Scopus citations

Abstract

The first measurements of the temperature dependence of a semiconductor's optical gap Eg(T) in the close vicinity of a critical point Tc are reported herein. The measurements were carried out on the ferromagnetic semiconductor CdCr2Se4 (Tc = 130.6°K) for which a well-known red shift of Eg(T) with decreasing temperature occurs. The results in the temperature range 10-1|t||TTc-1|5×10-4 are analyzed in terms of the specific-heat universal constants: the exponents α± and the ratio A+A-. It is found that with the constraint Tc+=Tc- the values α+=-0.020±0.004, α-=-0.038±0.003, and A+A-=0.60±0.05 are obtained. If the constraints α+=α-=-0.020orα+=α-=-0.038 are applied the ratio A+A-=0.64±0.05 is found. The present results, in accord with previous results of magnetization measurements, indicate clearly that the above |t| range is a transition region between mean-field and asymptotic critical behavior. This is understood to be due to the relatively long-range magnetic interactions in the present material.

Original languageEnglish
Pages (from-to)4535-4545
Number of pages11
JournalPhysical Review B
Volume16
Issue number10
DOIs
StatePublished - 1977

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