Magnetic interactions in the MnFe1−xCoxP series of solid solutions

Abstract

In this report the results of crystal structure investigations, high magneticfield measurements and electronic structure calculations carried out for theMnFe1−xCoxP system are presented. The crystal structure parameters were determined usingthe x-ray powder diffraction method. On this basis the inter-atomic distanceswere calculated and the magnetic couplings between magnetic atoms inMnFe1−xCoxP are discussed. Magnetic properties of the series of compounds withx = 0.3, 0.45, 0.5, 0.525, 0.55, 0.65 and 0.7, as determined under strong magnetic field(up to 20 T), are reported. The electronic band structure calculations wereperformed using the Korringa–Kohn–Rostoker method with the coherent potentialapproximation (KKR-CPA). The site preference of Co and Fe atoms, located inpyramidal and tetrahedral positions, was analysed and magnetic properties ofCo and Fe sublattices were calculated based on total energy computations. Thesite-decomposed densities of states and the magnetic moment values were calculated inthe whole alloy concentration range assuming a ferromagnetic (F) order. ForMnFe0.35Co0.65P the KKR-CPA calculations were carried out assuming different types of antiferromagnetic(AF) arrangement in order to elucidate the origin of the AF–F transition. The magneticinteractions between transition metal atoms, as established from the phenomenologicalanalysis of relating magnetic couplings and inter-atomic distances, were discussed based onthe evolution of the site-decomposed density of states and the corresponding dependence oflocal magnetic moments on alloy composition. A satisfying agreement betweenexperimental and calculated values of magnetization and local magnetic moments localizedon Mn, Co and Fe sites was found.