Spin reorientation process in Tm2–xHoxFe14B – analysis of conical arrangement based on Mössbauer spectra (original) (raw)
The spin reorientation process in the Tm2-xHoxFe14B 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 d...
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Journal of Alloys and Compounds, 2016
The series of Tm2−xTbxFe14B 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, αJ , a parameter which corresponds, however indirectly, to macroscopic magnetic anisotropy of the whole compound in which this ion is built in. Thulium (αJ > 0) exhibits strong planar magnetic anisotropy while terbium (αJ < 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 αJ on the spin reorientation process. All compounds were studied with 57 Fe 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.
Spin reorientation phenomena in Er2-xRxFe14B (R = Gd, Th) - Mössbauer and calorymetric study
Nukleonika
The Er 2−x Gd x Fe 14 B (x = 0.5, 1.0, 1.5) and Er 2−x Th x Fe 14 B (x = 0.0, 0.5, 1.0, 1.5, 2.0) polycrystalline compounds have been investigated with 57 Fe Mössbauer spectroscopy and differential scanning calorimetry (DSC). A comparison of results related to spin reorientation phenomena obtained for Gd-and Th-substituted compounds is presented in this paper. Spin reorientation phenomena (changes from planar to axial spin arrangements) have been studied extensively by a narrow step temperature scanning in the neighbourhood of the spin reorientation temperature, T SR. From the analysis of Mössbauer spectra, it was deduced that in the region of transition each subspectrum was split into two Zeeman sextets, which were characterised by different hyperfine magnetic fields and quadrupole splittings. A consistent way of fitting the spectra in the wide range of temperatures was proposed. The composition and temperature dependencies of hyperfine interaction parameters and subspectra contributions were derived from fits and the transition temperatures were determined for all the compounds studied. DSC studies proved that the spin reorientations were accompanied by thermal effects for all compositions of the Gd-and for x = 0.5 of the Th-series. Transformation enthalpy and T SR were determined from these studies and the two-stage character of transition was confirmed. Magnetic spin arrangement diagrams for R = Th and Gd series were constructed and compared using combined data obtained with both methods.
Acta Physica Polonica A, 2018
The series of Tm2−xTbxFe14B 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, αJ , a parameter which corresponds, however indirectly, to macroscopic magnetic anisotropy of the whole compound in which this ion is built in. Thulium (αJ > 0) exhibits strong planar magnetic anisotropy while terbium (αJ < 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 αJ on the spin reorientation process. All compounds were studied with 57 Fe 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.
Nukleonika
Two isostructural series of polycrystalline compounds: Er 2−x Y x Fe 14 B and Er 2−x Ce x Fe 14 B have been studied by 57 Fe Mössbauer spectroscopy in the temperature range 80−370 K. The spin reorientation phenomenon (a transition from basal plane to axial easy magnetisation direction) has been studied extensively by a narrow step temperature scanning in the vicinity of the transition. Using the procedure of subtracting the Mössbauer spectra taken for the same compound at different temperatures, it was possible to follow the influence of transition on the shape of spectra. From this procedure it was concluded that in the region of transition each subspectrum splits into two Zeeman sextets, which are characterised by different hyperfine magnetic fields and quadrupole splittings. The consistent way of describing the Mössbauer spectra was proposed. The spin reorientation temperatures have been established for all compositions and compared with the values obtained from theoretical calculations of spin orientation angle based on phenomenological model. The spin arrangement diagrams have been constructed.
Mössbauer studies of spin reorientations in Er2-xGdxFe14B
Nukleonika
The Er 2−x Gd x Fe 14 B (x = 0.5, 1.0, 1.5) polycrystalline compounds have been investigated with 57 Fe Mössbauer spectroscopy in the 80−330 K temperature range. The spin reorientation phenomena (changes from planar to axial spin arrangements) have been studied extensively by a narrow step temperature scanning in the neighbourhood of the spin reorientation temperature. From the analysis of the spectra it was deduced that in the region of transition each subspectrum was split into two Zeeman sextets, which were characterized by different hyperfine magnetic fields and quadrupole splittings. A consistent way of describing the Mössbauer spectra in the wide range of temperatures was proposed. The composition and temperature dependencies of hyperfine interaction parameters and subspectra contributions were derived from experimental spectra. The transition temperatures were determined for all the compounds studied.
Mössbauer Investigation of Spin Arrangements in Er2-xCexFe14B
Acta Physica Polonica A, 2008
It was theoretically postulated earlier that in compounds Er2−xCexFe14B it may be possible to observe not only axial and planar spin arrangements but also a conical one. In order to experimentally verify this hypothesis, 57 Fe Mössbauer spectroscopy analysis was used to study the polycrystalline compounds Er 2−x Ce x Fe 14 B in the postulated composition region (x = 1.0, 1.1, 1.2, 1.3) in the wide range of temperatures. The obtained experimental data do not clearly support the suggestion of conical arrangement occurrence in the postulated compositions. They indicate that such phenomenon may be shifted towards higher Ce content.
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