Local lattice distortions and magnetic properties of CdCr_2Se_(4-x)S_x

摘要

Interplay between structural disorder and magnetic interaction is investigated here for a multiferroic candidate material, CdCr_2Se_4. Ferromagnetic order in CdCr_2Se_4 sets in below T_C~ 130 K as a result of competition between the direct Cr-Cr spin coupling and the near neighbour Cr-Se-Cr exchange interactions. Hence, a small change in the crystal structure is expected to drastically affect its magnetic order. In this report, local lattice distortions within the overall cubic symmetry were brought about by replacing a small percentage of Se by isovalent 5. Detailed crystal structure study using EXAPS and Raman Spectroscopy reflects the presence of local distortions within the overall cubic symmetry. Contrary to the expectation, magnetic properties of the substituted compositions do not show any drastic changes. Though, a signature of spin-phonon coupling is present across the magnetic ordering temperature. No structural phase transition occurs within the investigated temperature range of 80-300 K.