Electronic structure analysis of the pressure induced metamagnetic transition and magnetovolume anomaly in Fe3C - Cementite

• Within the framework of ab initio electronic structure calculations we study a mechanism for the recently discovered pressure induced metamagnetic transition in Fe3C-cementite. It is shown that the transition occurs between a high moment ferromagnetic state and a non-magnetic (non-spin-polarized) state without stabilization of any intermediate antiferromagnetic-like state, which may explain the experimentally observed difference in character of the transitions in Fe3C and fcc Fe-Pt. Although both materials are Invar-type systems we find considerable differences between their electronic structures and the degrees of localization, or itinerancy, of the Fe magnetic moments. The possibilities for describing the thermal expansion anomaly in Fe3C within existing approaches to the Invar problem are discussed in detail.

Nyckelord

invar alloy

carbides

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