Frequency dependence of the transition temperature of the high-pressure magnetic phases in Fe68.1Ni31.9 and Co52.5Fe38Cr9.5

Abstract We have performed AC susceptibility measurements at various frequencies for high-pressure magnetic phases in Fe 68.1 Ni 31.9 and Co 52.5 Fe 38 Cr 9.5 Invar alloys. In the high-pressure magnetic phases of both alloys, χ ′– T curve shows a cusp, and the peak temperature of the cusp ( T P ) shifts to lower temperature side with decreasing frequency. The orders of the magnitude of the frequency shift of T P are similar to those of the spin glass phases and smaller than that of the super parramagnetism. In addition, the frequency dependences of T P almost follow with Vogel-Fulcher law. These results are corresponding to the previous report for the spin glass phases.