Data for: First Principles Theory of the Pressure Induced Invar Effect in FeNi Alloys

Amanda Ehn, Björn Alling, Igor A. Abrikosov

Department of Physics, Chemistry, and Biology (IFM), Linköping University, SE-581 83, Linköping, Sweden.

The Fe_0.64Ni_0.36 alloy exhibits an anomalously low thermal expansion at ambient conditions, an effect that is known as the invar effect. Other Fe_xNi_1-x alloys do not exhibit this effect at ambient conditions but upon application of pressure even Ni-rich compositions show low thermal expansion, thus called the pressure induced invar effect. We investigate the pressure induced invar effect for Fe_xNi₁-x`for x = 0.64, 0.50, 0.25 by performing a large set of supercell calculations, taking into account noncollinear magnetic states. We observe anomalies in the equation of states for the three compositions. The anomalies coincide with magnetic transitions from a ferromagnetic state at high volumes to a complex magnetic state at lower volumes. Our results can be interpreted in the model of noncollinear magnetism which relates the invar effect to increasing contribution of magnetic entropy with pressure.