First-order transition of Fe2P and anti-metamagnetic transition

A fixed-spin-moment (FSM) calculation is carried out for Fe2P using the linear muffin-tin orbital method. It is found that the Fe atom at the 3f site shows a metamagnetic behavior, while the Fe atom at the 3g site is ferromagnetic. In order to study the magnetic properties of this compound at finite temperatures. a simple model based on the Landau-Ginzburg theory is proposed, by taking into account the effect of spin fluctuations. The Landau parameters included in this model are estimated from the results obtained by fixed-spin moment band-calculations. It is shown that the first-order transition at T-C observed for Fe2P is attributed to the metamagnetic Fe atoms at the 3f site. The present mechanism of the first-order transition is connected with the anti-metamagnetic transition observed in some rare-earth and Co compounds.