Angular dependence of the upper critical field Bc2 for CeCu2Si2

The angular dependence of the upper critical field B c2 for A/S-type CeCu 2 Si 2 samples is determined. Both, the anisotropies within and outside the basal plane are measured using an angle-resolved resistivity technique, where an external magnetic field serves as a directional probe. Two high-quality A/S-type single crystals are studied (T N ~ 0.8 K, T c ~ 0.6 K). For the case where the magnetic field rotates within the basal plane, small variations of ~0.5% are observed and ascribed to sample misalignment. When the magnetic field rotates from the basal plane towards the [001] direction, a strong anisotropy of B c2 (~20%) is observed. By comparing the expected orbital- and Pauli-limiting fields, the strong effect of Pauli paramagnetism is realized. The latter is taken into account when using the anisotropic mass model to study the field anisotropy. Deviations are observed from such a conventional model.