Spontaneous Volume Magnetostriction and Lattice Constant of Face-Centered Cubic Fe-Ni and Ni-Cu Alloys

Abstract

Thermal expansion measurements were made on f.c.c. Fe-Ni and Ni-Cu alloys from liquid helium temperature up to 1000 K. The spontaneous volume magnetostriction of these alloys at 0 K evaluated from their thermal expansion curves can be quantitatively explained on the basis of the collective electron model, using the density of states curve for nickel. The lattice constants of these alloys at various temperatures evaluated from their thermal expansion curves deviate from Vegard's law in the Invar region. This deviation is discussed in connection with the magnetic state of the Invar alloy and with the origin of the Invar effects.