B.F. Bogacz

Unusual shape of the Mössbauer scattering line

Abstract The influence of the Rayleigh and Compton contributions to a Mossbauer scattering line is studied. A Mossbauer scattering spectrum of absorption character is theoretically predicted and experimentally observed for iron impurities in beryllium.

Hyperfine interactions and crystal site occupancies in RTiFe11−xCox (R=Y, Dy and Er) as seen by Mössbauer spectroscopy

Abstract RTiFe 11− x Co x (R=Y, Dy, Er) systems have been studied by 57 Fe Mossbauer spectroscopy at 295 and 78 K. The composition dependencies of hyperfine interaction parameters and the relative occupancies of Fe crystal sites by Co atoms were derived from the spectra. It was found that Co atoms strongly avoid the 8i sublattice and strongly prefer the 8f and 8j sites for the three studied systems. Some anomalies in behaviour of the quadrupole interaction were observed for ErTiFe 11− x Co x system which can be attributed to spin reorientation transition.

Mössbauer spectral and magnetic investigations of RFe10Cr2 compounds (R=rare earth)

Abstract The results of X-ray diffraction, magnetic susceptibility and Mossbauer investigations of RFe 10 Cr 2 intermetallic compounds (R=Y, Nd, Gd, Tb, Dy, Ho, Er and Tm) are presented and discussed. The variation with a sample composition of the lattice constants, unit cell volume, Curie temperature, iron and rare earth magnetic moments, magnetic anisotropy field and 57 Fe hyperfine interaction parameters are shown. The Curie temperatures of the RFe 10 Cr 2 series follow the same trend as in other R-Fe compounds and range from 466 K (for TmFe 10 Cr 2 ) to 585 K (for GdFe 10 Cr 2 ). Spin reorientation transition phenomena caused by the competition between the rare earth and iron sublattice magnetic anisotropies are observed for R=Tb, Dy and Er. The sample composition has little influence on the 57 Fe hyperfine interaction parameters. The numerical analysis of Mossbauer spectra shows that chromium atoms have a pronounced preference for occupying 8i sublattice in the whole series of the investigated compounds. From the magnetic susceptibility and Mossbauer data the approximate values of iron and rare earth magnetic moments are derived.

Investigation of YxFe80−xB20 and PrxFe80−xB20 amorphous alloys

Abstract The influence of Y and Pr on the magnetic properties of amorphous Y x Fe 80- x B 20 ( x = 0, 2, 4, 6 and 8) and Pr x Fe 80- x B 20 ( x = 2, 4 and 6) was investigated by Mossbauer spectroscopy and by magnetic measurements. It was found that the averaged value of 57 Fe hyperfine magnetic field, the value of the saturation magnetization and the Curie temperature decrease with the increase in Y or Pr content.

Experimental studies of spin reorientations in Er2−xPrxFe14B

57Fe Mossbauer spectroscopy, x-ray diffraction and magnetic measurements have been used to study the polycrystalline Er2−xPrxFe14B (x = 0.25, 0.5, 0.75, 1.0, 1.5) compounds. Special emphasis was put on the spin reorientation phenomena (change of spin orientation from planar to axial arrangement) occurring in this series. The spin reorientation in each compound has been investigated mainly by means of narrow step temperature scanning in the neighbourhood of the spin reorientation temperature, TSR. Initial magnetization versus temperature measurements allowed us to establish the temperature regions of reorientations and also the Curie temperatures of the compounds. Mossbauer temperature scanning was performed with a step of 2 K in the vicinity of TSR. The spectra obtained were analysed by using a procedure of simultaneous fitting and the transmission integral approach. Consistent fits were obtained; TSR and the composition dependences of hyperfine interaction parameters were derived from fits for all compounds studied. The TSR values obtained with both methods were compared and the spin phase diagram for the series was constructed.

Mössbauer and DSC studies of spin reorientations in Er2−xYxFe14B

Abstract Polycrystalline Er2−xYxFe14B (x=0.0, 0.5, 1.0, 1.5) compounds have been studied by 57Fe Mossbauer spectroscopy and differential scanning calorimetry (DSC) in the temperature range 80–370 K. The spin reorientation phenomenon has been studied extensively by narrow step temperature scanning in the vicinity of the spin reorientation temperature. Using the procedure of subtracting the Mossbauer 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 fields and quadrupole splittings. A consistent way of describing the Mossbauer spectra was proposed. The composition and temperature dependencies of hyperfine interaction parameters and subspectra contributions were derived from experimental spectra. Endothermic DSC peaks were observed for all compounds studied which correspond to the transition from basal plane to axial easy magnetisation direction. The spin reorientation temperatures and the enthalpies of transitions were established from the DSC data. A spin arrangement diagram was constructed and spin reorientation temperatures obtained by different methods were compared.

The Sound Field Around a Tuning Fork and the Role of a Resonance Box

Atypical two-tine tuning fork is barely audible when held vibrating at an arms length. It is enough, however, to touch its base to a table or, better, to a resonance box and the emitted sound becomes much louder. An inquiring student may pose questions: —Why is a bare tuning fork such a weak emitter of sound?—What is the role of the resonance box?—Where does energy connected with larger intensity of emitted acoustic waves come from?

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

Abstract 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 fitting procedure to investigate the influence of the transition on the shape of the spectra. The fitting program was specified to analyze the transition according to the ‘two state model’: spins flip abruptly from initial angle to final 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.

Mössbauer and calorimetric studies of spin reorientation processes in Er2-xPrxFe14C.

The Er2?xPrxFe14C (x = 0.25, 0.5) poly crystalline compounds have been synthesized and investigated by means of X-ray diffraction, 57Fe M?ssbauer spectroscopy and Differential Scanning Calorimetry (DSC). The influence of carbon on the spin reorientation phenomena with increasing praseodymium content was of special interest in these compounds. Investigations of spin reorientation phenomena were performed by means of 57Fe M?ssbauer spectroscopy with a narrow step temperature scanning in the neighborhood of the spin reorientation temperature. Obtained M?ssbauer spectra were analyzed using a procedure of simultaneous fitting and the transmission integral approach. Consistent description of Mossbauer spectra were obtained. 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 revealed weak thermal effect (heat absorption) during the transition process. Heat absorption was detected only for the compound with the lowest content of Pr (x = 0.25). The results obtained with different methods were analyzed and data were compared with those for Er2?xPrxFe14B series. The spin arrangement diagram was constructed.

Crystal and magnetic properties of Y2(Fe1−xMx)14B(M = Cu or Cr) compounds

Abstract The influence of the partial substitution of iron by copper or chromium on the crystal and magnetic properties of Y2Fe14B has been investigated with X-ray diffraction, magnetometric and Mossbauer effect methods. The substitution of iron by chromium results in the linear decrease in both the a and c lattice constants. The opposite effect is observed when iron is replaced by copper. The Curie temperature decreases when iron is substituted by chromium but it increases when copper replaces iron. The substitution process leads to a decrease in saturation magnetization of both series of compounds. In contrast to copper, the substitution of chromium for iron has a great influence on the 57Fe hyperfine magnetic fields which cannot be accounted for by the random distribution of the substituent atoms among iron crystal sites.