Critical Phenomena in an Itinerant Antiferromagnet of γ Fe0.5Mn0.5

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 0.5 Mn 0.5 . It has been found that the maxima of C m , dρ/d T and dχ(0)/d T 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.