Magnetic ordering in CeMnCuSi2

Abstract Temperature and field-dependent magnetization measurements on polycrystalline CeMnCuSi 2 reveal that the Mn moments in this compound exhibit ordering with a ferromagnetic (FM) component ordered instead of the previously reported purely antiferromagnetic (AFM) ordering. The FM ordering temperature, T c , is about 120 K and almost unchanged with external fields up to 50 kOe. Furthermore, an AFM component (such as in a canted spin structure) is observed to be present in this phase, and its orientation is modified rapidly by the external magnetic field. The Ce L 3 -edge X-ray absorption result shows that the Ce ions in this compound are nearly trivalent, very similar to that in the heavy fermion system CeCu 2 Si 2 . Large thermomagnetic irreversibility is observed between the zero-field-cooled (ZFC) and field-cooled (FC) M ( T ) curves below T c indicating strong magnetocrystalline anisotropy in the ordered phase. At 5 K, a metamagnetic-type transition is observed to occur at a critical field of about 8 kOe, and this critical field decreases with increasing temperature. The FM ordering of the Mn moments in CeMnCuSi 2 is consistent with the value of the intralayer Mn–Mn distance R a Mn–Mn =2.890 A, which is greater than the critical value 2.865 A for FM ordering. Finally, a magnetic phase diagram is constructed for CeMnCuSi 2 .