Neutron depolarization measurements on the reentrant spin-glass bcc Cr-Fe-Mn alloy

Abstract

Neutron depolarization and diffraction measurements were performed on bcc Cr60Fe20Mn20 with the aim of studying the low temperature reentrant spin-glass phase. This alloy is reported to undergo successive magnetic transitions as the temperature is lowered, viz., antiferromagnetic, ferromagnetic and spin glass. Transmitted neutron polarization was measured as a function of temperature for zero-field-cooled (ZFC) and field-cooled (FC) cases. The transition to a ferromagnetic phase is indicated by a decrease in the polarization at TC~100 K. It exhibits a minimum at 55 K below which it increases and at 14 K, in the spin-glass phase, for the ZFC case it recovers to the paramagnetic value. Large irreversibility and time dependent effects are also observed in the spin-glass phase. These results indicate that the ferromagnetic order which grows below TC is destroyed in the spin-glass phase at 14 K. Neutron diffraction measurements indicate the presence of an antiferromagnetic (100) peak below TN~290 K. The intensity of the (100) peak increases as the temperature is lowered and persists down to 15 K. The low temperature phase is, therefore, a mixed phase where spin-glass and antiferromagnetic order coexist.