Relaxation process of magnetic moments in chromium-doped Invar alloys

Invar alloys Ni31(Fe69-xCrx) x=3, 4, 6 and 8 (at.%) in the temperature range 120-400 K have been studied by magnetic and Messbauer methods. It is find out the absence of a magnetic hyperfine structure of 57Fe nuclei in the magnetically ordered temperature range for alloys with x=6 and 8. The magnetic structure of the alloys can be represented as a system of superparamagnetic clusters, the magnetic moments of which relax between differently populated energy levels. The phenomenon is explained by the increased frequency of relaxation of magnetic moments between these levels. Keywords: invar alloy, magnetization, Curie temperature, magnetic moment, relaxation process, Messbauer effect.