Low field magnetic studies of some Gd1-xLax alloys

Polycrystalline pure Gd and Gd1-xLax (x = 0.15, 0.25, 0.27 and 0.50) alloys have been studied by low field magnetic susceptibility (chi(AC)). magnetiz ation and electrical resistivity measurements. Measurements were also perfo rmed on samples with low demagnetizing factor geometry in order to study th e ground state properties of these systems. For hexagonal close-packed (hcp ) samples the effect of spin reorientation is indicated by a broad peak in the susceptibility curve and it shifts rapidly to lower temperatures with i ncreasing La content in Gd metal. The spin reorientation effect is not obse rved in the samples with La concentration higher than 15%. The chi(AC) and resistivity measurements indicate a ferromagnetic transition at T-C = 225 K for 15% La concentration. For the Sm-type structure sample, with x = 0.27, two magnetic transition peaks are observed at 135 K and 113 K and helical antiferromagnetic order is suggested. Finally, the results for the x = 0.50 alloy with double hexagonal close-packed (dhcp) crystalline structure indi cate a spin-glass magnetic phase type, below T-g = 30 K. Observed magnetiza tion remanent effects, in this latter case, give additional support for the presence of the spin-glass phase.