THEORY OF MAGNETIZATION IN Pb1-xMnxTe AND Pb1-xEuxTe

Abstract

We present in this work a theory of magnetization (M) in diluted magnetic semiconductors and express it as sum of contributions due to magnetic impurities (M i ) and band effects which include lattice diamagnetism (M dia ) and spin density due to carriers (M c ). In addition to the contribution of isolated magnetic ions (Ms), M i includes the contributions of three types of small clusters: pairs (M p ), open triplets (M ot ) and closed triplets (M ct ). The contributions due to impurity spin interactions were calculated using modified Heisenberg's Hamiltonian as applicable to these clusters within the nearest neighbor interaction approximation. The band effects include contributions due to lattice diamagnetism and spin density due to carriers. The lattice diamagnetism χ dia was calculated using a two band model for the host system and a modified one for the alloy systems. χ dia for the host system compare well with the available experimental results. M c was calculated using a formula derived from first principles for an interacting electronic system. This is modified to calculate M c in the p-type Pb 1-x Mn x Te and Pb 1-x Eu x Te . Although the band effects are found to be small in the context of analyzing magnetization, they are intrinsically important in the sense that these quantities shed light on the nature of mechanisms contributing to lattice diamagnetism and the carrier spin densities in these systems.