Magnetic properties of MBE‐grown Zn _{1− <i>x</i>} Cr _<i>x</i> Te

Abstract

We have grown Zn1−xCrxTe films by molecular-beam-epitaxy (MBE) and investigated their magnetic properties with variation of Cr concentrations (x) between 0.01–0.08. Systematic increase of the lattice constant was observed by XRD only up to around x = 0.02. Measurements of the magnetizations M–H reveal that ferromagnetic transition occurs in the films at low temperatures. The transition temperature (TC) which was estimated from Arrott-plots increased with Cr concentration up to about 100 K for x = 0.08. However, the temperature dependence of the magnetization M-T shows different curves below TC for field-cooled (FC) and zero-field-cooled (ZFC) processes. Moreover, their paramagnetic Curie temperatures (Θ), estimated from the higher temperature M-T curves, are different from and much higher than TC. These behaviours could be attributed to the superparamagnetism in the films. Indeed, many defects such as stacking faults are observed in the sample with x = 0.08 through HRTEM. It could give rise to the distribution of the Cr concentrations and/or the presence of precipitates including Cr. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)