Magnetization and specific heat of nanocrystalline rare-earth TbAl₂, TbCu₂ and GdAl₂ alloys

Measurements of the magnetization and specific heat on nanocrystalline TbAl₂, TbCu₂ and GdAl₂ with mean particle diameters below 40 nm show a different behavior from those made on bulk alloys. A reduction of the saturation magnetization quantified in TbAl₂from 8.4 μ_B/mol for the bulk to 5.8 μ_B/mol for a 14 nm alloy is attributed to a spin disordered layer on the particle surface. In the specific heat, the lambda anomaly associated to the ferro (Δc = 6.6 J/molK, 9.8 J/molK) and to the antiferromagnetic transitions (7.1 J/molK) in the bulk samples, respectively, is smeared out due to finite size effects.