Structure and magnetic properties of layered compounds RMn1.7Cr0.3Si2C (R = Nd, Sm, Dy)

The carbon doped RMn1.7Cr0.3Si2C (R = Nd, Sm, Dy) compounds were prepared by arc melting and investigated using room temperature (RT) X-ray diffraction (XRD), neutron powder diffraction (NPD) and magnetic measurements. Carbon atoms were found to occupy the interstitial site (0, 0, 0.125) in a superstructure with the space group P4/mmm at room temperature. There exists a disordered substitution between the R atoms and corresponding Si dumbbells on the same layer perpendicular to c direction in the carbides. The Mn/Cr sublattice of the carbides exhibits ferromagnetic characteristics at room temperature despite of a very short intralayer interatomic distance (dMn-Mn = 2.796 Å for R = Dy), which is far below the critical distance for a ferromagnetic (dMn-Mn >2.87 Å) ordering of Mn sublattice due to the strong hybridization between the interstitial C and the Mn/Cr atoms. Different phase transitions of the carbides have different response to the external magnetic field. These carbides provide the potential for further research on magneto-transport properties and magnetocaloric effect. Additionally, spin reorientation was observed in SmMn1.7Cr0.3Si2C owing to the competence of magnetocrystalline anisotropy between the Mn/Cr sublattice and the Sm sublattice.