Anomalous magnetic response of CeRu₂

Long ago S. B. Roy and co-workers had explored the appearance of anomalous paramagnetic response in the magnetization data near the H_C2 phase boundary in samples of CeRu2. Recently, an anomalous paramagnetic response has also been demonstrated in a Boro-carbide superconductor LUM₂B ₂C, where the phenomenon has been related to the symmetry transition of the flux line lattice. We report here the magnetization data from vibrating sample magnetometer in a single crystal of CeRu₂. We demonstrate that the magnetization profile is dipolar like only at very low fields and as the applied field increases it gets drastically modified. The presence of quadrupole moment along with the dipole moment is needed to justify such a magnetization profile. We report that the quadrupole moment undergoes a large modulations near the H_C2 phase boundary. Hence, there is a possibility of response from quadrupole moment getting mixed with that from dipolar response which might lead to paramagnetic anomaly prior to H_c2.