Spin reorientation process in Tm_2–xHo_xFe₁₄B – analysis of conical arrangement based on Mössbauer spectra

The spin reorientation process in the Tm_2-xHo_xFe₁₄B series of compounds was studied using ⁵⁷Fe Mössbauer spectroscopy over the temperature range 5.2-320 K with a focus on the analysis of conical spin arrangement. Each compound was studied by precise Mössbauer scanning in the vicinity of the transition and during the transition. By applying computer simulations based on the simplified Yamada-Kato model, as well as on some literature data for R₂Fe₁₄B (R = Tm, Ho) compounds, the above series was selected for studies as it contains compounds with different spin arrangements (axial, planar, conical). It was a crucial requirement for obtaining unambiguous angular dependences when applying a simultaneous fitting procedure of Mössbauer spectra. Such an extended procedure was applied which allowed the temperature dependence of the angle describing the position of the magnetization vector to be obtained. The results were compared with those from theoretical simulations. The spin arrangement diagram was constructed. A conical spin arrangement was confirmed over a wide temperature range.