Study of phase stability in NiPt systems

Abstract

Abstract. We have studied the problem of phase stability in NiPt alloy system. We have used the augmented space recursion based on the TB-LMTO as the method for studying the electronic structure of the alloys. In particular, we have used the relativistic generalization of our earlier technique. We note that, in order to predict the proper ground state structures and energetics, in addition to relativistic effects, we have to take into account charge transfer effects with precision.

Local environment effects in the magnetic properties and electronic structure of disordered FePt

“…As found earlier [23,29], the difference between moments for ordered and disordered FePt is evident but not large. The variation in µ spin between different SQS's is quite small when going stepwise from N = 4 to N = 32.…”

“…Studies of 2 local environment effects focused on charge transfer and energetics [2, [19][20][21][22]. Few studies dealt also with shortrange order effects on magnetic moments [23,24]. Comparison between theory and experiment shows, nevertheless, that the CPA is often able to describe the trends of physical properties with alloy composition very well [15,17,18,25,26].…”

“…Kharoubi et al [28] investigated the electronic structure, the complex Kerr angle and the magnetic moments for ordered and disordered FePt multilayers and performed a complete analysis of the strong Kerr rotation with respect to photon energy. Paudyal et al [23] calculated the electronic structure and magnetic properties of ordered and disordered FePt, CoPt and NiPt alloys. Their main concern was a comparison between the ordered and disordered phases and the variation of the magnetic moments with alloy composition.…”

Spin–orbit coupling: a recursion method approach

“…Singh [4] and Paudyal et al [5] have argued that unless we include at least the scalar relativistic corrections for NiPt, we cannot predict the observed low temperature ordering in the 25% , 50% and 75% composition alloys. Scalar relativistic corrections are now routinely incorporated in most electronic structure calculations for both ordered compounds as well as disordered alloys.…”

“…Usually by s = 4 we reach bulk behavior [13,14], R s refers to the position of an ion-core on the surface labelled by s. The potential parameters depend upon the surface label. This is because the charge densities, being dependent on the local environment, depend upon s and in the LSDA, the charge densities uniquely determine the Metal/Alloy Structure equilibrium lattice parameter in amstrong unit [5] We have to remember that the total energy per atom, which is minimized in LSDA calculations should contain the Madelung terms due to the surface dipole layer formed by charges leaking out of the surface [15]. In order to take care of the charge leakage, we have added a layer of empty spheres carrying charge but no ion-cores in the layer labelled s = -1.…”