ELECTRONIC STRUCTURE CALCULATIONS OF FERROMAGNETIC AND PARAMAGNETIC STATE IN MAGNETOCALORIC SYSTEMS: Mn_(1-x)T_xAs and Fe_(2-x)T_xP

摘要

We present results of electronic structure calculations for two promising MCE materialsrnMn_(1-x)T_xAs and Fe_(2-x)T_xP (T= transition elements) by the Korringa-Kohn-Rostoker method withrncoherent potential approximation (KKR-CPA). In this work, KKR-CPA was used not only torninvestigate properties of chemically disordered systems, but also to simulate paramagnetic staternusing the 'disordered local moments' (DLM) concept. In order to enlighten modifications ofrnelectronic structure in the vicinity of ferromagnetic-paramagnetic (FM-PM) transition, density ofrnstates (DOS), total and local magnetic moments, were calculated in MnAs and Fe_2P. Our KKRCPArncomputations show, that magnetic moment on Fe(3f) disappears in PM state in Fe2P, whilernthat one on Fe(3g) remains almost unchanged, with respect to the FM state. It yields strongrnmodifications of DOS near E_F. In MnAs, the calculated magnetic moment on Mn in PM (O) isrnsmaller than that one in FM (H), which also results in DOS modifications near E_F. We alsornpresent the remarkable variation of local magnetic moments with T impurity in Mn_(1-x)T_xAs.rnFinally, using the calculated DOS in FM and PM the effect of both magneto-elastic transitionrn(Fe_2P) as well as magneto-structural transition (MnAs) on electronic part of entropy is discussed.