Crystal field and magnetic anisotropy in tmfez
Author
Al-Saririyah, Muna Ali Ahmed
English abstract
The RFez compounds where R is a rare earth element have been extensively studied over the past 40 years. However, the TmFez compound still present some unresolved challenges. In particular there is ambiguity concerning the direction of spontaneous magnetization at low temperatures. This ambiguity remained because the crystal field in TmFez places the material almost at a boundary where there is a change-over in direction of spontaneous magnetization.
The aim of the present work is to remove this ambiguity and to perform a detailed analysis of the crystal field in TmFez. Mössbauer spectroscopy was used to determine the direction of spontaneous magnetization at low temperatures and magnetometry combined with crystal-field computations were used to review the crystal field Hamiltonian. It was found that at low temperatures the direction of spontaneous magnetization is in the [111] direction and that the conventional three parameter model is not sufficient to describe the Tm** ion in TmFez. It is proposed that distortions due to magnetostriction are significant in this material and that therefore a second-order term must be introduced in the crystal-field Hamiltonian.
