Electron spin resonance in Cd<i>x</i>Zn<i>y</i>Mn<i>z</i>Te alloys

Abstract

Electron spin resonance (ESR) studies were made on the Mn2+ constituent of CdxZnyMnzTe (x+y+z=1) polycrystalline semimagnetic semiconductors, covering the whole range of solid solutions available, alloys with 0.10≤z≤0.75 being used. These materials exhibit spin-glass properties at low temperatures. The temperature dependence of the Mn2+ ESR linewidths were measured in the samples between 4.2 to 300 K, and it was found in each case that the linewidth increased with decreasing temperature, reaching a maximum value at a critical temperature Tc. The temperature variation of the linewidths were found to fit a theoretical expression of the form ΔH=A[Tc/(T−Tc)]α, where ΔH is the linewidth, A is a constant, Tc is the critical temperature and α is the critical exponent. The percolation limit for any ratio of x:y was found to be in the range 0.20≤z≤0.25. For values of z above this limit, Tc was found to vary smoothly with z for fixed x:y ratios, showing a linear variation in the limiting case of Zn1−zMnzTe , and all the lines extrapolated to a value of Tc=305 K for MnTe. For fixed values of z the values of Tc were found to increase linearly with y. The value of α was found in each case to fall within the range 0.33±0.08. In some samples an extra line of width ∼100 G was found superimposed on the main ESR line, and it is attributed to clustering of Mn2+ ions in the structures, with the resultant line from the cluster being exchange narrowed.