Critical Phenomena in an Itinerant Antiferromagnet of γ Fe_0.5Mn_0.5

抄録

Critical phenomena of various physical properties such as sublattice magnetization (⟨S_Q^z⟩), static susceptibility χ(0), specific heat (C_m), electrical resistivity (ρ_m) and thermo-electric power (S) of γ FeMn alloys have been measured for three different specimens with composition close to Fe_0.5Mn_0.5. It has been found that the maxima of C_m, dρ⁄dT and dχ(0)⁄dT occurs about 9 degrees below the Néel temperature T_N where (⟨S_Q^z⟩) disappears and the longitudinal staggered susceptibility (χ_⁄⁄(Q)) diverges and χ(0) gives the maximum. ρ and S also show an anomaly at T_N. Such a curious phenomenon has been understood if we assume that the Néel temperature is distributed in the sample with the standard deviation of 5 degrees and with the maximum cut off of 495 K.