AN ULTRASONIC STUDY OF SPIN-DENSITY-WAVE EFFECTS IN A CR-PERCENT IR ALLOY SINGLE-CRYSTAL(0.2 AT)

Measurements of the temperature dependences of the second-order elasti c constants and attenuation of ultrasonic waves through the magnetic p hase transition temperatures of a Cr+0.2 at. % Ir alloy single crystal are reported. The incommensurate-commensurate spin-density-wave trans ition is marked by steplike decreases, accompanied by hysteresis of wi dth about 16 K, in all the elastic constants on heating through the tr ansition temperature. The attenuation coefficient shows a spikelike pe ak at this transition. A deep minimum in c(11) and small peaks in c(44 ) and 1/2 (c(11)-c(12)) observed at the Neel transition. (C) 1996 Amer ican Institute of Physics.