Antiferromagnetically-Coupled Ferrimagnetic Layer Structure in CsMnF₃and Ni-Doped CsMnF₃

Abstract

Magnetization of CsMnF 3 and Ni-doped CsMnF 3 has been measured in the temperature range between 1.6K and 300K and in the magnetic field up to 70 kOe. It has been observed that the susceptibility increases very rapidly with decreasing temperature below T N and that the susceptibility of Ni-doped CsMnF 3 decreases with increasing magnetic field. This behavior is qualitatively explained from a detailed analysis of the four-sublattice model of molecular field theory. The exchange integrals in CsMnF 3 are evaluated to be J A B =6.8 K for the 180°-superexchange and J B B =4.5 K for the 90°-superexchange assuming that all the next-nearest exchange are 0.1 K. The 90°-superexchange between Mn and Ni in Ni-doped CsMnF 3 are estimated to be about -8.5 K. With these parameters CsMnF 3 is found to have an antiferromagnetically-coupled ferrimagnetic layer structure.