ACTA

From Flip to Slow Rotation-Spin Reorientation Process in Tm_2-xTb_xFe₁₄B Observed by Mössbauer Spectroscopy

P.M. Kurzydło^a, A.T. Pędziwiatr^a, B.F. Bogacz^a, R. Gargula^a, J. Przewoźnik^b
^aM. Smoluchowski Institute of Physics, Jagiellonian University, S. Łojasiewicza 11, 30-348 Kraków, Poland
^bAGH University of Science and Technology, Faculty of Physics and Applied Computer Science, Department of Solid State Physics, al. A. Mickiewicza 30, 30-059 Kraków, Poland

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The series of Tm_2-xTb_xFe₁₄B compounds with tetragonal crystal structure was selected for studies as it contains a mix of competing rare-earth ions which are characterized by exactly opposite values of the Stevens coefficient, α_J, a parameter which corresponds, however indirectly, to macroscopic magnetic anisotropy of the whole compound in which this ion is built in. Thulium (α_J>0) exhibits strong planar magnetic anisotropy while terbium (α_J<0) exhibits strong axial magnetic anisotropy. Following earlier studies for Er-based compounds, a series of Tm-based compounds with x=0, 0.1, 0.3 was synthesized as they were likely to show spin reorientation process, allowing to study a path of the transition, angle of conical arrangement, and an influence of α_J on the spin reorientation process. All compounds were studied with ⁵⁷Fe Mössbauer spectroscopy in the temperature range 80-330 K with precision scanning in the vicinity of the spin transition. Experimental data were processed using simultaneous fitting procedure which includes a flipping and rotation of spins during the reorientation process. A computer simulation of spin reorientation process based on the Yamada-Kato model was conducted. As a summary, a spin arrangement diagram was constructed.

DOI:10.12693/APhysPolA.134.1036
PACS numbers: 75.25.-j, 75.50.Ww, 76.80.+y, 78.70.Ck