High-field discontinuity in the magnetisation of SmCo3Cu2 and SmCo2.5Cu2.5

Abstract An unusual jump from low to high magnetisation in increasing applied field is observed in isotropic bulk Sm(CoCu) 5 between 30 K and close to the Curie temperature. Clear hysteretic behaviour is detected in the magnetisation curves during a cycle of increasing and decreasing field. No anomaly appears in the magnetisation, if a field is applied along the magnetically easy axis in aligned powder and also in some as-cast bulk samples. Contrary to the discontinuity observed on RCo 5 compounds with R atoms as Th and Ce, the critical field, where the transition occurs, increases with decreasing temperature. Therefore, the origin of the discontinuity is discussed in terms of an onset of a non-collinear magnetic structure.