THE MULTICRITICAL REGION OF THE GD-LU ALLOY SYSTEM

The magnetic phase diagram of the Gd-Lu alloy system has been studied in the multicritical region using ultrasound velocity and attenuation measurements and neutron diffraction. A phase diagram has been drawn u p on the basis of these measurements. The phase diagram has much in co mmon with that of Gd-Y including the existence of a ferro I phase in w hich a net c-axis moment coexists with a paramagnetic distribution of spins in the basal plane. For Lu concentrations greater than 23.5% a h elical antiferromagnetic (HAF) phase exists. At low temperatures all o f the samples studied exhibit a canted ferromagnetic structure. The HA F-to-canted-ferromagnetic transition occurs when the pitch of the heli x approaches zero and there is a small temperature range (approximate to 2 K) over which canted ferromagnetic and HAF domains coexist.