Sublattice Magnetization and the Exchange Interaction in TbzY1−zSb

Elastic neutron scattering has been used to measure the sublattice magnetization of TbzY1−zSb for z=1, 0.91, 0.66, and 0.64. The moment/Tb at 0°K are 7.83, 7.57, 7.43, and 7.07 μB; and the TN are 15.2, 13.4, 8.85, and 8.5°K respectively. These TN are quite close to those found in the same samples by susceptibility measurements, also used to fix the concentrations. The sublattice magnetizations and TN are in good agreement with the behavior expected for an exchange field (Heff) proportional to z and varying linearly with the moment/Tb (M). The linear exchange field coefficient (λ) is about 15% larger than that found in earlier bulk magnetic measurements in the paramagnetic regime, z≤ 0.403; and in contrast to the earlier work there is little, if any, need for contributions to Heff with higher order dependence on M.