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1

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.

2

Mössbauer and heat capacity studies of ErZnSn2

Łątka K., Przewoźnik J., Żukrowski J., Verbovytskyy Y., Gonçalves A. P.

Nukleonika

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2017

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Vol. 62, No. 2

129--133

EN

Heat capacity results obtained for the intermetallic compound ErZnSn2 were re-analysed to also consider, apart from the classical Debye model, the anharmonicity of the crystal lattice and the proper set of Einstein modes. The 119mSn Mössbauer technique was applied to derive the hyperfine interaction parameters characteristic of the two inequivalent crystallographic Sn sites in the compound studied. Quadrupole interaction constants, as measured by 119mSn Mössbauer spectroscopy, allowed for estimations of Vzz components of the electric field gradient tensor that exist at both Sn sites in the discussed compound.

3

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.

4

Analysis of heat capacity and Mössbauer data for LuZnSn2 compound

Łątka K., Przewoźnik J., Żukrowski J., Verbovytskyy Y., Gonçalves A. P.

Nukleonika

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2015

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Vol. 60, No. 1

97--101

EN

New analysis of heat capacity data is presented for LuZnSn2 compound that takes into account anharmonic effects together with the existence of Einstein modes. 119mSn Mössbauer spectroscopy was used to monitor the hyperfi ne parameters at the two crystallographically inequivalent Sn sites in the studied compound. The problem of non-unique mathematical resonance spectrum description and the problem how to choose physically meaningful set of hyperfi ne parameters will be thoroughly discussed. Measured quadrupole interaction constants by 119mSn Mössbauer spectroscopy give estimations for Vzz component of electric fi eld gradient tensor at both Sn sites in LuZnSn2.

5

Structural, magnetic, and Mössbauer effect studies of bornite

Przewoźnik J., Żukrowski J., Gondek Ł., Lemański A., Kapusta C., Piestrzyński A.

Nukleonika

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2013

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Vol. 58, No. 1

43-46

EN

The results of a combined study of bornite with Mossbauer spectroscopy, X-ray diffraction and DC magnetometry are reported. The orthorhombic crystallographic structure of the mineral is observed at 15 K and 300 K. It exhibits an increase of the orthorhombic distortion with decreasing temperature. Magnetic susceptibility shows a Curie-Weiss like behaviour between 230 K and 380 K corresponding to the effective magnetic moment of 7.2(3) mi B per formula unit. The material undergoes a transition to an antiferromagnetic-like state at 75 K. Mossbauer spectra at the paramagnetic range are doublets with a small quadrupole splitting and the isomer shift corresponding to a high spin Fe3+ state. Upon magnetic ordering, a coexistence of the paramagnetic doublet with a broadened magnetic sextet is observed indicating an inhomogeneous character of the magnetic transition. The hyperfine field of 350 kOe at 4.2 K is much lower than that observed for a high spin Fe3+ in oxides (510 kOe) which is attributed to covalence effects and a possible copper contribution to the effective magnetic moment of the compound.

6

Hyperfine interactions and irreversible magnetic behavior in multiferroic Aurivillius compounds

Jartych E., Gąska K., Przewoźnik J., Kapusta C., Lisińska-Czekaj A., Czekaj D., Surowiec Z.

Nukleonika

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2013

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Vol. 58, No. 1

47-51

EN

In this work investigations of structure and magnetic properties of conventionally sintered Bim+1Ti3Fem.3O3m+3 compounds with 4 less-than or equal to m less-than or equal to 8 were performed using X-ray diffraction, Mossbauer spectroscopy and vibrating sample magnetometry. Room-temperature Mossbauer spectra of the compounds correspond to a paramagnetic state, however, low temperature measurements (80 K) reveal the antiferromagnetic state with a residual paramagnetic phase. Temperature dependencies of magnetic susceptibility,chi sigma(T), provided magnetic ordering temperatures and revealed an irreversibility in Aurivillius compounds with m greater-than or equal to 5. In the case of Bi5Ti3FeO15 compound the chi sigma(T) dependence shows a paramagnetic behavior down to 2 K. The Bi6Ti3Fe2O18 compound reveals a magnetic ordering at 11 K. The compounds with m = 6-8 show a magnetic ordering at temperatures higher than 200 K. Highly irreversible character of their temperature dependencies of chi sigma indicates a spin-glass type disordered magnetism with frustration due to a random distribution of Fe on Ti at their sites.

7

The influence of high temperature plastic deformation on magnetic properties of Ni2MnGa type single crystals

Szczerba M. J., Przewoźnik J., Żukrowski J., Kapusta Cz., Szczerba M. S., Major B.

Archives of Metallurgy and Materials

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2009

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Vol. 54, iss. 2

439-447

EN

The work presents experimental results on the influence of high temperature plastic deformation on the magnetic properties of Ni2MnGa type single crystals. It has been shown that room temperature plasticity of the Ni2MnGa single crystals is limited to very small strains (lower than 10-2), whereas at 1073K these single crystals could be plastically compressed to strains greater than 5x10-1. Magnetic properties of deformed and undeformed samples have been studied in low and high magnetic field. The analysis of the obtained magnetic hysteresis at different temperatures indicate a significant impact of the plastic deformation on the coercive field and the remanent magnetization (an increase by a factor of 3) and a lack of the effect on the saturation magnetization.

PL

W pracy przedstawiono wyniki doświadczalne dotyczące wpływu wysokotemperaturowej deformacji plastycznej na własności magnetyczne monokryształów typu Ni2MnGa. Wykazano, iż plastyczność badanych monokryształów Ni2MnGa w temperaturze otoczenia jest ograniczona do bardzo małych odkształceń, nie większych niż 10-2, natomiast w 1073K badane monokryształy można ściskać do odkształceń wiekszych niż 5x10-1. Przeprowadzono badania własności magnetycznych w małym oraz w dużym polu na próbkach przed i po procesie wysokotemperaturowego ściskania. Analiza pętli histerezy magnetycznej uzyskanych przy różnych temperaturach wskazuje na istotny wpływ odkształcenia plastycznego na zwiększenie wartości pola koercji oraz namagnesowania resztkowego (około trzykrotne) i jego brak na wartość namagnesowania nasycenia.

8

Spin and lattice dynamics of La2/3Ca1/3MnO3 doped with 1% 119Sn

Przewoźnik J., Żukrowski J., Chmist J., Japa E., Kołodziejczyk A., Krop K., Kellner K., Gritzner G.

Nukleonika

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2004

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Vol. 49,suppl.3

37-42

EN

1 at.% 119Sn doped La0.67Ca0.33MnO3 compound was studied by Mössbauer spectroscopy, magnetization, AC susceptibility and resistivity measurements. Huge separation (66 K) of the transition temperatures from the ferromagnetic (FM) to paramagnetic (PM) state (TC) and from metallic to insulating state (TM-I) clearly shows that transition from FM metallic to PM insulator phase goes via FM insulator phase. The Mn lattice dynamics was studied by the relative changes of Lamb-Mössbauer factor f as a function of temperature. In the Debye approximation from the calculated ln(f/f0) values of the characteristic Debye temperatures (čD) were estimated for the FM (368(10) K) and PM (391(6) K) phases. No anomaly of -ln(f/f0) at TM-I and its rather spurious increase around TC was found. The 119Sn isotope as a local diamagnetic probe samples the transferred hyperfine field (Bhf) from its neighbour Mn magnetic moments and witnesses the dynamics of the Mn moments. Theoretical curve based on the molecular field theory was fitted to the experimental values of Bm hf ax and the value of the ordering temperature (TC * H 280 K) of Mn moments inside the large FM domains was estimated. It is much higher than the TC (172 K) obtained from magnetization measurement. The coexistence of FM and PM phases, which is evident from the shape of our 119Sn Mössbauer spectra, was confirmed for temperatures T e 150 K and indicates the inhomogeneous character of the magnetic transition.