Search results

1

Perturbed γ-γ Angular Correlation Studies of Isostructural Ag_{5}Zn_{8} and Ag_{5}Cd_{8} Intermetallic Compounds

100%

Wodniecki P., Wodniecka B., Marszałek M., Hrynkiewicz Α. Z.

Acta Physica Polonica A

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1995

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vol. 88

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issue 2

333-338

EN

Perturbed γ-γ angular correlation spectroscopy was applied to study hyperfine interaction parameters for ^{111}In probes in intermetallic compounds of D8_{2} structure. The perturbed γ-γ angular correlation spectra measured in Ag_{5}Zn_{8} and Ag_{5}Cd_{8} phases reflect a number, population and symmetry of nonequivalent substitutional sites occupied by the indium probes. The temperature dependences of the observed electric field gradients were measured in the temperature range 37-500 K

2

Crystallochemical Structure of Tourmalines Inferred from Mössbauer Spectroscopy

100%

Kraczka J., Pieczka A.

Acta Physica Polonica A

|

2001

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vol. 100

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issue 5

743-750

EN

In the Y octahedra of tourmalines theoretically may occur ions of Fe^{2+} and Fe^{3+}. The authors discuss Mössbauer measurements and confirm the ordered model of ionic distribution at these sites: the presence of Fe^{3+} ions in the Y octahedra and Al^{3+} ions in the Z octahedra. The spectra of different tourmalines annealed at temperatures ranging from 873 K to 1153 K show that Fe^{3+} ions can occur in both of these sites. The annealing has changed the symmetry of the neighbourhood of iron ions at the octahedral sites. It has been shown that the doublets with QS<2.00 mm/s should not been attributed to Fe^{2+}(Z). Also new results corroborating the existence of the iron ions in the mixed valence state in tourmalines have been presented.

3

Local States of Tellurium in Isolated Helical Chains

100%

Stanek J., Fornal P., Hafner S., Pfitzner A.

Acta Physica Polonica A

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2001

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vol. 100

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issue 5

807-815

EN

The local electronic state of Te in the helical chains of CuXY_{2(1-x)}Te_{2x} (X = Cl, Br; Y = Se, S) were studied using the Mössbauer spectroscopy of ^{125}Te at 10 K and 70 K. The isolated chains of Te in these compounds are less rigid than those in elemental Te. The determined data of quadrupole splittingΔ and Debye temperatureΘ_D are indicative of strong local ordering of Te in one of the two non-equivalent crystallographic positions. It was not possible to resolve crystallographic positions by the Mössbauer spectroscopy.

4

Magnetic Moment and Electronic Structure of Amorphous Alloys of the Type Fe_{80-x}TM_{x}B_{20}

63%

Nowakowska A., Dudek W., Oleniacz J., Zych W.

Acta Physica Polonica A

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1994

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vol. 86

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issue 6

1027-1036

EN

Magnetic properties of amorphous alloys of the type Fe_{80-x}TM_{x}B_{20} (0 ≤ x ≤ 20 at.%, TM = Ni, Co, Mn, Cr, V, Ti) are presented and analyzed. The basis of our research work was the Mössbauer measurements, magnetic saturation measurements, derivative thermo-magnetogravimetry and differential thermal analysis measurements. The magnetic moments are discussed in terms of Friedel's virtual-bound-state model for light TM impurities in strong ferromagnets. Some conclusions about the electronic structure are presented.

5

Magnetic Susceptibility Disaccommodation and Mössbauer Effect in Microcrystalline Fe-Si Ribbons

63%

Ciurzyńska W.

Acta Physica Polonica A

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2000

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vol. 97

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issue 4

719-728

EN

The magnetic susceptibility disaccommodation of the microcrystalline Fe-xSi (x=3, 5, 6.5, and 7.2 wt%) ribbons in the as-quenched state and after annealing at 1370 K for 1 h was investigated in the temperature range from 220 to 410 K. Simultaneously, the microstructure of those samples was studied using the Mössbauer spectroscopy. It is found that the isochronal disaccommodation curves may be decomposed into five elementary processes. Taking into account the results obtained from the Mössbauer spectra analysis, the relaxational process with activation energy equal to 0.84 eV may be considered as the Snoek relaxation. However, the relaxational processes of higher activation energy seem to be connected with jumps of C atoms in the vicinity of Fe atoms surrounded by 1, 2, 3, and 4 silicon atoms.

6

Temperature Dependence of Magnetization in Transition Metal Ultrathin Films of Various Thicknesses

63%

Świrkowicz R.

Acta Physica Polonica A

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1991

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vol. 80

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issue 5

689-697

EN

Temperature dependence of the local magnetization in the spin-wave regime is calculated within the framework of the multiband model for ultrathin films consisting of 5, 7 and 9 monolayers. The temperature range in which the calculated results can be fitted to the Bloch T^{3/2} law is found in all cases. The Bloch coefficient Bay corresponding to temperature dependence of the average film magnetization is found to be proportional to 1/D, where D is the thickness of the film. The spatial distribution of the local magnetization is obtained. The Bloch coefficient corresponding to the surface layer appears to be greater than the one corresponding to the central layer, namely B_{s} > B_{c}. The ratio B_{s}/B_{c} is increasing with an increase of the film thickness. The calculated results are well consistent with experimental ones obtained for ultrathin films of various thicknesses.

7

Structural Relaxation in Fe_{78}Nb_{2}B_{20} Amorphous Alloy Studied by Mössbauer Spectroscopy

63%

Kansy J., Hanc A., Rasek J., Haneczok G., Pająk L., Stokłosa Z., Kwapuliński P.

Acta Physica Polonica A

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2011

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vol. 119

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issue 1

41-43

EN

It was shown that soft magnetic properties of Fe_{78}Nb_{2}B_{20} amorphous alloy can be significantly improved by applying 1-h annealing at temperature 623 K (permeability increases even about 8 times). The Mössbauer Spectroscopy technique indicated that the optimized microstructure (corresponding to the maximum magnetic permeability) is free of iron nanograins and should be attributed to annealing out of free volume and a reduction of internal stresses i.e. to the relaxed amorphous phase.

8

New Graphical Interface to the MOSGRAF Suite

63%

Duraj Ł., Ruebenbauer K.

Acta Physica Polonica A

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2011

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vol. 119

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issue 1

75-77

EN

A contribution is devoted to the recent development of the MOSGRAF suite used to process Mössbauer data and to generate reference functions for the modern spectrometers of the MsAa-x (x=1, 2, 3, 4) family. Newly developed interface is designed for the Microsoft Windows-XP® or higher system of this class. However one can use some older system of this class as well provided some plug-ins are installed additionally. The lowest useable system is Microsoft Windows-98® - 32-bit edition. The new version of the MOSGRAF suite is compatible with 32-bit and 64-bit systems. MOSGRAF is fully compatible with MsAa-x spectrometers, however a powerful tool to convert ASCII data files from other spectrometers is provided. Data processing programs are compiled by the high efficiency Fortran-90 Lahey-Fujitsu® compiler. One of the most important new features is the ability to process velocity calibration data obtained by the new method based on the measurement of the time lapse between fringes of the Michelson-Morley interferometer.

9

Maximum Entropy Method in Mössbauer Spectroscopy - a Problem of Magnetic Texture

63%

Satuła D., Szymański K., Dobrzyński L.

Acta Physica Polonica A

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2011

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vol. 119

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issue 1

78-80

EN

A reconstruction of the three dimensional distribution of the hyperfine magnetic field, isomer shift and texture parameter z from the Mössbauer spectra by the maximum entropy method is presented. The method was tested on the simulated spectrum consisting of two Gaussian hyperfine field distributions with different values of the texture parameters. It is shown that proper prior has to be chosen in order to arrive at the physically meaningful results.

10

Experimental Evidence for Jahn-Teller Transition in a Fe(II)Fe(III) Bimetallic Oxalate

63%

Tang G., He Y., Xu F., Zhang Q.

Acta Physica Polonica A

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2013

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vol. 123

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issue 1

118-120

EN

Bimetallic oxalate {[N-(n-C_4H_9)_4][FeFe(C_2O_4)_3]}_{n} has been investigated by the Mössbauer spectroscopy. The Mössbauer studies confirm that high-spin Fe(III) (S=5/2) and Fe(II) (S=2) ions are present in the compound. These spectra above 60 K consist of three quadrupole doublets, indicating that there are three different Fe sites in the material. The Mössbauer results reveal that spontaneous magnetization of Fe(II) sublattices increases more steeply than that of Fe(III) sublattices as the temperature decreases from T_{C}. Great increase of quadrupole splitting at 50 K provides compelling evidence for the predicted Jahn-Teller transition.

11

Magnetic Properties of Fe_3O_4 Films on Fe(001)

63%

Zając M., Aernout D., Freindl K., Matlak K., Spiridis N., Ślęzak M., Ślęzak T., Korecki J.

Acta Physica Polonica A

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2007

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vol. 112

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issue 6

1318-1325

EN

We investigated the magnetic properties of ultrathin magnetite films deposited directly on MgO(001) and on a Fe(001) buffer layer. In both cases the magnetite surface structure could be identified using low energy electron diffraction. The conversion electron MÖssbauer spectroscopy measurements proved that, for magnetite films deposited on the Fe buffer, superparamagnetic relaxation was strongly suppressed. The effect of a Fe overlayer on the magnetite film grown directly on MgO is considerably weaker. Longitudinal Kerr magnetometry indicated the presence of the ferromagnetic interfacial coupling between Fe and magnetite films. We conclude that the density of antiphase boundaries for films grown on the Fe buffer is lower than that of Fe_3O_4/MgO films.

12

Mössbauer-Effect Study of Calciomagnetites

63%

Dubiel S., Cieślak J., Orewczyk J., Jasieńska S.

Acta Physica Polonica A

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1998

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vol. 93

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issue 3

547-561

EN

Ca_{x}Fe_{3-x}O_{4} samples, with x ≤ 0.28 , prepared from α-Fe_{2}O_{3} and CaO by the Bridgman method were investigated by means of ^{57}Fe Mössbauer spectroscopy. Room temperature spectra gave evidence that the samples were multiphase, the calciomagnetite being the dominant phase with a contribution of 73% to 99%, depending on the sample. Analysis of the subspectra associated with the calciomagnetite gave evidence that Ca-ions reside on the tetrahedral (A) sites and have not random distribution. Their presence on those sites causes a reduction of the hyperfine field at Fe nuclei occupying the octahedral positions (B) by 12.3(1.0) kOe per one Ca-ion and a decrease in the average hf field, 〈H_{B}〉/dx, at the rate of 29 kOe/mol% for x ≤ 0.07 and of 387 kOe/mol% for larger x. In addition, a linear correlation between 〈H_{B}〉 and the average isomer shift, 〈I_{B}〉, was revealed to hold. It indicates that addition of Ca-ions into the magnetite causes a decrease in the spin-density and an increase in the charge-density at Fe nuclei occupying the B-sites.

13

Process of Amorphization Induced by Mechanical Alloying of Iron with Tungsten and Niobium

63%

Jartych E., Oleszak D., Żurawicz J.

Acta Physica Polonica A

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2001

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vol. 100

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issue 5

731-736

EN

Mechanical alloying method was used to synthesise powders of iron with tungsten and niobium. Mössbauer spectroscopy and X-ray diffraction have been applied to monitor the progress in solid-state reactions. In the case of Fe-W system, exhibiting a positive heat of mixing, no trace of amorphization was observed for 20 and 33 at.% of W, as the calculations of phase diagram (CALPHAD) method suggest. During the mechanical alloying process, two solid solutions Fe(W) and W(Fe) were obtained. Mössbauer measurements allowed to recognise the Fe(W) solid solution as a ferromagnetic phase, while the W(Fe) solid solution as a paramagnetic one. In the case of Fe-Nb system, exhibiting a negative heat of mixing, single phase amorphous alloys were synthesised during mechanical alloying of iron with 48 and 64 at.% of Nb. For both investigated compositions, the final products of mechanical alloying processes were amorphous paramagnetic alloys.

14

High-Pressure Mössbauer Studies of Magnetism in ScFe_2 and Sc_{0.4}Ti_{0.6}Fe_2 Laves Phases

63%

Rupprecht K., Lu J., Wortmann G., Przewoźnik J., Żukrowski J.

Acta Physica Polonica A

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2001

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vol. 100

|

issue 5

789-797

EN

We report on ^{57}Fe-Mössbauer studies of the magnetic properties in ScFe_2 and Sc_{0.4}Ti_{0.6}Fe_2 performed as a function of pressure and temperature. Both systems crystallize in the C14-type Laves phase structure with two different Fe sites 6h and 2a. The ferromagnetic properties of ScFe_2 (T_C=540 K at ambient pressure) change around 30 GPa to antiferromagnetic order of the 6h sites with non-magnetic 2a sites. The ordering temperature is lowered to T_N=300 K at 51 GPa. This pressure-dependent behaviour of ScFe_2 resembles that observed within the Sc_{1-x}Ti_xFe_2 series as a function of x. In ferromagnetic Sc_{0.4}Ti_{0.6}Fe_2 we observe, as a function of temperature and of pressure, an abrupt high-moment to low-moment transition of the Fe band moments of the 6h sites, accompanied by a rearrangement of the spin directions. In both systems the decrease in the Fe moments is accompanied by a strong increase in the volume coefficient of the isomer shift, originating from a reduced s-electron shielding capability of the d-electrons in the low-moment state.

15

Local versus Bulk Properties of CeAg_{2}Sn_{2}

63%

Görlich E.

Acta Physica Polonica A

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1994

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vol. 85

|

issue 2

253-257

EN

Results of electrical resistivity and ^{119}Sn Mössbauer effect measurements for two samples of CeAg_{2}Sn_{2} compound are presented. A sharp drop in resistance of an annealed sample at 3.5 K might have suggested a superconducting transition while for the as-melted specimen only a modest change in ρ vs. T slope is observed at this temperature. Resonance γ-absorption reveals differences and similarities on a microscopic scale between the two samples. The occurrence of certain regions of a long-range magnetic ordering within the CeAg_{2}Sn_{2} phase is unambiguously demonstrated by the presence of hyperfine splitting. Temperature variation of the hyperfine field follows a molecular field spin-½ function.

16

Electronic and Magnetic Properties of Y(FeV)_{12} Compound and its Carbides

63%

Deniszczyk J., Borgieł W.

Acta Physica Polonica A

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1997

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vol. 91

|

issue 2

459-462

EN

Electronic and magnetic properties of body centered tetragonal YFe_{8}V_{4} carbon doped compounds were determined by tight-binding linear muffin-tin orbitals method assuming experimental values of lattice constants. Total, partial densities of states and magnetic moments for YFe_{8}V_{4} and its carbides for different positions of carbon within unit cell of parent compound were calculated and discussed. In spite of carbides' unit volume decrease enhancement of magnetization and Curie temperature were obtained. Results are in quantitative agreement with experimental data.

17

A Search for Thermal Vacancies Forming Close Frenkel Pairs in Fe-Cr Alloys

63%

Chojcan J.

Acta Physica Polonica A

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2001

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vol. 100

|

issue 5

723-729

EN

The room temperature Mössbauer spectra of ^{57}Fe were measured for the bcc Fe_{0.948}Cr_{0.052} solid solution quenched into water being at about 295 K from different temperatures not exceeding 1000 K, i.e. from the temperatures for which probabilities of formation of "clear" (Schottky) vacancies as well as vacancies forming the separate interstitial-vacancy (Frenkel) pairs are negligibly low. The obtained data were analysed in terms of concentration of unoccupied places in the 14-site surroundings of an ^{57}Fe Mössbauer probe in the sample. It turned out that the concentration of vacancies detected by the probe increases with temperature very rapidly - at the rate of about 10^{-4} K^{-1}. The result may suggest that the Mössbauer probe is sensitive to a possible thermal distortion of the lattice or creation of very close Frenkel pairs (the interstitial is the nearest neighbour of the vacant lattice site).

18

Charge and Spin Density Perturbation on Iron Nuclei by Non-Magnetic Impurities Substituted on the Iron Sites in α-Fe

63%

Błachowski A.

Acta Physica Polonica A

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2008

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vol. 114

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issue 6

1563-1571

EN

The paper is aimed at the review of the charge and spin density perturbation on the iron nucleus in the bcc iron-based binary alloys containing as the impurity either 4d (Nb, Mo, Ru, Rh, Pd) or 5d (Os, Ir, Au) metals. Additionally, Ga was used as such impurity as well. Measurements were performed by means of the ^{57}Fe transmission Mössbauer spectroscopy at room temperature. Powder X-ray diffraction data for alloys investigated show linear dependence of the lattice constant versus impurity concentration. The Mössbauer data were treated assuming random distribution of the impurity over the iron sites and additive effect for the charge density perturbation, and additive in the algebraic sense effect for the corresponding spin density perturbation. Hence, the effect of impurity depends solely on the distance between impurity and the iron nucleus under above assumptions. It has been found that impurities being further away than a third or in some cases as the second neighbor do not contribute directly to the charge and spin perturbation. On the other hand, they have usually some minor effect on the average charge and spin density. Generally, the perturbation to either charge or spin density has some oscillatory character versus distance from the impurity. The phase and period of the charge oscillation is vastly different from the phase and period of the spin oscillation in the majority of cases. Substitution of the impurities with the increasing number of 4d or 5d electrons leads to the lowering of the electron density on the iron nucleus and causes decreased band spin density on this nucleus. Subsequent impurities donate more and more d-type electrons to the band, and the latter screen more and more effectively s-like electrons. Hence, the density of the s-like electrons on the iron nucleus diminishes. Impurities with 5d electrons have generally stronger effect on the charge and spin density perturbation than impurities with 4d electrons.

19

A Dilute-Limit Heat οf Solution of Aluminium in Iron Studied with ^{57}Fe Mössbauer Spectroscopy

63%

Chojcan J., Ostrasz A.

Acta Physica Polonica A

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2008

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vol. 114

|

issue 6

1573-1578

EN

The room temperature ^{57}Fe Mössbauer spectra for binary iron-based solid solutions Fe_{1-x}Al_x, with x in the range 0.03 ≤ x ≤ 0.05, were analysed in terms of binding energy E_b between two Al atoms in the Fe-Al system. The extrapolated values of E_b for x= 0 were used for computation of the dilute-limit heat of solution of aluminium in iron. The results were compared with that resulting from the Miedema's model of alloys as well as those derived from the heat of formation of the system, obtained with both calorimetric measurements and theoretical calculations. The comparison shows that our Mössbauer spectroscopy findings are in good agreement with all the other results mentioned above.

20

Properties of SmT_{2}Sn_{2} (T = Ni,Cu) Phases

63%

Görlich E. A., Kmieć R., Łątka K., Pacyna A.

Acta Physica Polonica A

|

1997

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vol. 92

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issue 2

319-322

EN

Ternary compounds SmNi_{2}Sn_{2} and SmCu_{2}Sn_{2} were investigated with the X-ray diffraction, magnetic susceptibility and electric resistivity methods, as well as using the ^{119}Sn Mossbauer effect under the applied magnetic field. Magnetic susceptibilities of these compounds show the Curie-Weiss behaviour in the temperature range from 15 K to 280 K with the enhanced values of the temperature independent term χ_{0}. Both resistivity and magnetic measurements indicate the occurrence of the magnetic ordering in SmCu_{2}Sn_{2} below T_{N} = 8 K. The Mossbauer investigations carried out at 4.2 K under an applied magnetic field of up 6 T indicate a more complex magnetic structure and a considerable anisotropy. SmNi_{2}Sn_{2} remains paramagnetic down to 5 K.

Refine search results

Perturbed γ-γ Angular Correlation Studies of Isostructural Ag_{5}Zn_{8} and Ag_{5}Cd_{8} Intermetallic Compounds

Crystallochemical Structure of Tourmalines Inferred from Mössbauer Spectroscopy

Local States of Tellurium in Isolated Helical Chains

Magnetic Moment and Electronic Structure of Amorphous Alloys of the Type Fe_{80-x}TM_{x}B_{20}

Magnetic Susceptibility Disaccommodation and Mössbauer Effect in Microcrystalline Fe-Si Ribbons

Temperature Dependence of Magnetization in Transition Metal Ultrathin Films of Various Thicknesses

Structural Relaxation in Fe_{78}Nb_{2}B_{20} Amorphous Alloy Studied by Mössbauer Spectroscopy

New Graphical Interface to the MOSGRAF Suite

Maximum Entropy Method in Mössbauer Spectroscopy - a Problem of Magnetic Texture

Experimental Evidence for Jahn-Teller Transition in a Fe(II)Fe(III) Bimetallic Oxalate

Magnetic Properties of Fe_3O_4 Films on Fe(001)

Mössbauer-Effect Study of Calciomagnetites

Process of Amorphization Induced by Mechanical Alloying of Iron with Tungsten and Niobium

High-Pressure Mössbauer Studies of Magnetism in ScFe_2 and Sc_{0.4}Ti_{0.6}Fe_2 Laves Phases

Local versus Bulk Properties of CeAg_{2}Sn_{2}

Electronic and Magnetic Properties of Y(FeV)_{12} Compound and its Carbides

A Search for Thermal Vacancies Forming Close Frenkel Pairs in Fe-Cr Alloys

Charge and Spin Density Perturbation on Iron Nuclei by Non-Magnetic Impurities Substituted on the Iron Sites in α-Fe

A Dilute-Limit Heat οf Solution of Aluminium in Iron Studied with ^{57}Fe Mössbauer Spectroscopy

Properties of SmT_{2}Sn_{2} (T = Ni,Cu) Phases