Temperature effects on the optical energy gap values of CdxZnyMnzTe alloys

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Abstract
Wavelength modulated reflectance measurements were made on a wide range of CdxZnyMnzTe alloys to determine the variation of the energy gap E0 as a function of temperature in the range 10–300 K. It was shown that in the vicinity of the spin‐glass transition temperature Tg, there is a magnetic contribution ΔE which increases E0, and ΔE was determined as the difference between the experimental values and a simple Manoogian–Leclerc extrapolation from higher temperatures. These values of ΔE were fitted to the relation (dt/dt)(ΔE)=−Pt−μ where t=‖T−Tg‖/Tg and good agreement found with the theoretical predictions of Alexander et al. for the effect on the band gap of a critical point such as Tg. As predicted, different behavior was observed close to Tg and at temperatures outside the critical region, μ having a value close to zero in the first range and close to 0.5 in the second. The values of P were very similar for both ranges, extrapolating to zero at the nearest‐neighbor percolation limit of z=0.18 and showing a discontinuity in slope in the vicinity of z∼0.6 where a transition from spin‐glass to antiferromagnetic behavior occurs.