The high-temperature paramagnetic susceptibility of the system (Fe1-xMnx)2P

Abstract

For the system (Fe1-xMnx)2P(O<or=x<or=1), numerous previous studies have shown that Fe- and Mn-rich solid solutions crystallise with a hexagonal symmetry (H) and intermediate compositions are of orthorhombic type (O). The H and O phases are those generally encountered in the transition-metal pnictides of formula MM'X(M,M': transition metal; X:P or As). Analysis of the paramagnetic state at the highest temperatures reveals the stability of the H structure for the whole system. The magnetic transition observed at high temperature for intermediate ranges of composition can be related to the crystal O to or from H transformation already observed by neutron diffraction. In most of the cases, a metastable hexagonal phase can be retained by ensuring fast quenching. A complete phase diagram versus composition and temperature, is proposed. The reciprocal paramagnetic susceptibility behaviour as temperature is varied provides evidence for large magnetic correlations far above the ordering temperature for the hexagonal form only. For a given composition, a strong influence of the local metal environment on the magnetic couplings is thus emphasised for both H and O forms of the MM'X series.