MAGNETO-VOLUME EFFECTS IN FE-NI INVAR - A 1ST PRINCIPLES THEORY

A complete theory of the magnetic properties, the magneto-volume effect, and the thermal properties of weak itinerant ferromagnets is proposed in terms of spin- and volume fluctuations. This theory combines the results of band structure calculations (only valid at 0 K) with fluctuation models including temperature effects. We use the results of previous spin-polarised band structure calculations performed with the fixed-spin-moment (FSM) method using the local spin density approximation for exchange and correlation, where the total energy is obtained as a function of volume and the magnetic moment. The fluctuations are treated classically within the frame of a Ginzburg-Landau theory. Numerical results are given for the Fe-Ni invar system. © 1989.