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Spin reorientation process in Tm2–xHoxFe14B : analysis of conical arrangement based on Mössbauer spectra

Kurzydło P. M., Pędziwiatr A. T., Bogacz B. F., Przewoźnik J., Oleszak D.

Nukleonika

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2017

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Vol. 62, No. 2

123--127

EN

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 diagram was constructed. A conical spin arrangement was confirmed over a wide temperature range.

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Search for canted spin arrangement in Er2-xTbxFe14B with Mössbauer spectroscopy

Kurzydło P. M., Bogacz B. F., Pędziwiatr A. T., Oleszak D., Przewoźnik J.

Nukleonika

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2015

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Vol. 60, No. 1

93--96

EN

The materials studied were polycrystalline compounds Er2-xTbxFe14B (x = 0.1, 0.2, 0.3, 0.4) which crystallize in a tetragonal lattice and display a variety of spin arrangements. The compounds have been measured with 57Fe Mössbauer spectroscopy over the temperature range 80–320 K in order to investigate the spin reorientation processes. Each compound was studied in a wide temperature range, with precise Mössbauer scanning in the vicinity of the transition. The set of spectra obtained for a given compound was analyzed using simultaneous fi tting procedure to investigate the infl uence of the transition on the shape of the spectra. The fi tting program was specifi ed to analyze the transition according to the ‘two state model’: spins fl ip abruptly from initial angle to fi nal arrangement (90° angle). Obtained results suggest that spin reorientation process cannot be described using only the mentioned above model. Additional computer simulations based on the Yamada–Kato model were conducted to determine temperature range and the type of spin alignments in the vicinity of the transition. These theoretical results supported by spectra analysis suggest the existence of intermediate (canted) spin arrangements in the studied compounds. The spin arrangement diagram was constructed.

3

Crystal electric field parameters determination for R2Fe14B compounds based on Yamada - Kato model

Bogacz B. F., Pędziwiatr A. T.

Nukleonika

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2013

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Vol. 58, No. 1

31-33

EN

Semi-empirical model developed by Yamada-Kato enables calculation of magnetic spin directions for R2Fe14B compounds, based on minimization of free energy, and - in further steps - determination of spin reorientation temperatures for transitions from basal plane to axial easy magnetization direction. In our study, this model has been successfully used to determine crystal field and exchange field parameters for Er2-xCexFe14B compounds based on spin reorientation temperatures obtained experimentally from Mössbauer measurements.

4

Structure, magnetic and electrical transport properties of Mn4-xAgxN compounds

Feng W. J., Li D., Zhang Q., Deng Y. F., Ma S., Zhang Z. D.

Materials Science Poland

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2009

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Vol. 27, No. 1

33--42

EN

Mn4-xAgxN compounds (x = 0.0, 0.3, 0.6, 1.0) were prepared by milling and subsequently annealing the mixture of Mn2N0.86, Mn, and Ag powders. All compounds display good single-phase characteristics. Both Mn4N and Mn3.7Ag0.3N exhibit ferrimagnetism, and a little Ag replacement of Mn can improve the saturation magnetization. The magnetic transition of Mn3.4Ag0.6N and Mn3AgN below 15 K is from triangular antiferromagnetism to non-coplanar ferrimagnetism, while the ones at 256 and 275 K (Mn3.4Ag0.6N and Mn3AgN, respectively) have been ascribed to the gradual transition, as temperature increases, from the triangular antiferromagnetic structure T5g to a ferrimagnetic-like one. Two minima appear on the p(T) curves for Mn3AgN, with the observation of a positive magnetoresistance throughout the whole tempeature-dependent change.

5

Spin reorientation phenomena in Er2-xRxFe14B (R = Gd, Th) – Mössbauer and calorimetric study

Wojciechowska A., Pędziwiatr A., Bogacz B., Wróbel S.

Nukleonika

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2007

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Vol. 52, supl. 1

77-79

EN

The Er2 xGdxFe14B (x = 0.5, 1.0, 1.5) and Er2 xThxFe14B (x = 0.0, 0.5, 1.0, 1.5, 2.0) polycrystalline compounds have been investigated with 57Fe 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, TSR. 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 TSR 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.

6

Mössbauer studies of spin reorientations in Er2-xGdxFe14B

Wojciechowska A., Bogacz B., Pędziwiatr A.

Nukleonika

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2004

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Vol. 49,suppl.3

71-73

EN

The Er2 xGdxFe14B (x = 0.5, 1.0, 1.5) polycrystalline compounds have been investigated with 57Fe 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.

7

Spin arrangement diagrams for Er2-xRxFe14B (R = Y, Ce) obtained with Mössbauer spectroscopy and phenomenological model

Pędziwiatr A., Bogacz B., Gargula R.

Nukleonika

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2003

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Vol. 48,suppl.1

59-63

EN

Two isostructural series of polycrystalline compounds: Er2-xYxFe14B and Er2-xCexFe14B have been studied by 57Fe 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.