Magnetic measurements on HgMnTe epitaxial layers

Abstract

Magnetization measurements have been performed on epitaxial layers of Hg1−xMnxTe (MMT) using an alternating gradient field magnetometer (AGFM). The layers, which have a Mn concentration in the range 0.05<x<0.20, and thicknesses between 1 and 6 μm, are deposited by metalorganic vapor phase epitaxy (MOVPE) techniques. The MMT films are grown on GaAs substrates with CdTe and ZnTe buffer layers. Growth is achieved by the interdiffused multilayer process (IMP), where alternate layers of HgTe and MnTe are deposited, and then heated, to produce diffusion and, hence, Hg1−xMnxTe. The MnTe layers that are grown are roughly 1 nm thick, and so grow in the cubic structure, rather than the nickel arsenide structure observed in the bulk material.1 The magnetization of the majority of the samples is the expected paramagnetic behavior with values of χ close to those observed in the bulk material.2 However, a number of the samples have shown evidence for magnetic order at room temperature, and this is also observed in MnTe layers grown by MOVPE. The samples showing saturation of the magnetization also shown an anomalous behavior of the Hall voltage below 100 K and at fields up to 0.3 T. The anomalies in the HgMnTe samples are thought to be due to MnTe inclusions left over from the MOVPE growth process