A.V. Ruban, S. Khmelevskyi, P. Mohn, B. Johansson:

"Magnetic state, magnetovolume effects, and atomic order in Fe";_{65}Ni_{35}Invar alloy: A first principles study\

Physical Review B,76(2007), 0144201 - 0144209.

We employ the locally self-consistent Greenīs function technique and exact muffin-tin orbital method to

investigate magnetic state and ground state properties of Invar Fe65Ni35 alloy. We show that it is in a chemically

disordered state, characterized by a relatively small amount of atomic short-range order, above the

magnetic ordering temperature. We speculate that it should remain in this state below the Curie temperature

upon applying usual heat treatment for the Invar alloys. The magnetic state at the experimental lattice spacing

is shown to be sensitive to the type of approximation for the exchange-correlation functional: While the

magnetic ground state is purely ferromagnetic in the generalized gradient approximation, there is a small

amount of Fe atoms with magnetic moment antiferromagnetically aligned relative to the global magnetization

in the local density approximations. The local spin-density approximation, however, fails to yield correctly the

equilibrium lattice spacing, whereas the generalized gradient approximation reproduces it reasonably well. The

anomalous spontaneous volume magnetostriction leading to the Invar effect is found to be approx. 3%, in fair

agreement with the experimental estimate of approx. 2.2%.\

Created from the Publication Database of the Vienna University of Technology.