Magnetization study of γ-Fe80−xNixCr20(14⩽x⩽30) alloys to 20 T

Abstract

Very-high-field (0--20 T) dc-magnetization measurements M(H) and M(T) between 4.2--60 K and 19--700 K, respectively, have been carried out on substitutionally disordered \ensuremath{\gamma}-${\mathrm{Fe}}_{80\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Ni}}_{\mathrm{x}}$${\mathrm{Cr}}_{20}$ (14 \ensuremath{\leqslant}x\ensuremath{\leqslant} 30), austenitic stainless steel alloys having a wide variety of exotic magnetic phases. Distinct functional relationships M(H) have been found in different magnetic phases below their respective transition temperatures. In a ferromagnetic (FM) alloy with x=30, contributions from long-wavelength spin-wave and Stoner single-particle excitations have been found in the temperature-dependent demagnetization process. In the light of the Rhodes-Wohlfarth criterion, this alloy is found to be a weak-itinerant FM. For the alloys with x=26 and 23 (mixed or reentrant phase) the coexistence of long-range FM ordering along with spin-glass (SG) freezing has been established supporting the Gabay-Toulouse model. For x=21 and 19 (SG), the field-dependent magnetization (after scaling) falls on a single universal curve, which implies the same kind of response dynamics of the frozen spins. For an antiferromagnetic (AFM) alloy with x=14, a spin-flop transition has been observed at 1 T due to the canting of the AFM spins in the strong external magnetic field. The long-range AFM structure of this alloy is found to be of type 1.