P. Pawlik

Influence of lanthanum on structural and magneto-optic properties of diamagnetic glasses of the TeO2–WO3–PbO system

This paper is focused on the design, fabrication and characterization of tellurite glass of composition TeO2–WO3–PbO in terms of La2O3 addition. The effect of La2O3 on the structure of the obtained glasses has been investigated by means of spectrophotometric and ellipsometric measurements in the UV-Vis-NIR spectral region and then relevant optical parameters have been calculated. The DC magnetic susceptibility study has been used to investigate the influence of lanthanum ion (La3+) on the structural and magnetic properties of the investigated glass system. Based on DTA, PALS and Raman studies, it can be stated that modification of the basic structural units with La3+ ions, namely the TeO4 trigonal bipyramid (tbp) and the TeO3 trigonal pyramid (tp), both having a lone pair of electrons occupying one of the equatorial positions, affect the magnetic properties of these glasses.

Nanocrystalline (Pr,Dy)-(Fe,Co)-Zr-Ti-B magnets produced directly by rapid solidification

Hard magnetic thick ribbon samples of a series of Pr9-xDyxFe60Co13Zr1+yTi3-yB14 alloys (where x=0;1 and y=0;1) (having average thicknesses tr of~ 140 µm) were produced directly by the melt-spinning technique under an Ar atmosphere. The phase constitution of the samples in the as-cast state was determined by X-ray diffractomety and Mossbauer spectroscopy. Hysteresis loops measurements at room temperature indicated very good hard magnetic properties for the alloys, which the coercivity attaining a maximum values of 1.58 MA/m. This is comparable with the coercivities of commercial NdFeB magnets based on melt spun ribbon and with those for nanocrystalline Nd-Fe-B magnets produces by other processes such as mechanical alloying or HDDR.

Iron Doped SBA-15 Mesoporous Silica Studied by Mössbauer Spectroscopy

Mesoporous silica SBA-15 containing propyl-iron-phosphonate groups were considered to confirm their molecular structure. To detect the iron-containing group configuration the Mossbauer spectroscopy was used. Both mesoporous silica SBA-15 containing propyl-iron-phosphonate groups and pure doping agent iron acetylacetate were investigated using Mossbauer spectroscopy. The parameters such as isomer shift, quadrupole splitting, and asymmetry in 57Fe Mossbauer spectra were analyzed. The differences in Mossbauer spectra were explained assuming different local surroundings of Fe nuclei. On this base we were able to conclude about activation of phosphonate units by iron ions and determinate the oxidation state of the metal ion. To examine bonding between iron atoms and phosphonic units the resonance Raman spectroscopy was applied. The density functional theory DFT approach was used to make adequate calculations. The distribution of active units inside silica matrix was estimated by comparison of calculated vibrational spectra with the experimental ones. Analysis of both Mossbauer and resonance Raman spectra seems to confirm the correctness of the synthesis procedure. Also EDX elemental analysis confirms our conclusions.

Correlation Between The Size Of Nd60Fe30Al10 Sample, Cast By Various Techniques And Its Coercivity

The present study is concerned with the correlation between the magnetic properties of the Nd60Fe30Al10 sample and its size, in particular its dimension measured in the direction of heat removal. We compared samples produced using the three methods: melt‐spinning, die casting under pressure, and suction casting. The samples were of various shapes such as ribbons, plates, rods and pipes. We found that despite the differences in the shape of the samples and the technique of their casting, their magnetic properties did not differ significantly. Hence we may conclude that it is the sample dimension measured along the direction perpendicular to the heat‐removing surface which is the parameter that mostly decides about the cooling rate.

Rotational hysteresis and magnetization reversal mechanisms in Sm–Fe–N permanent magnets

Abstract The mechanism of magnetization reversal processes in Sm–Fe–N permanent magnets has been investigated on the basis of the analysis of the rotational hysteresis energy, W r , calculated from the magnetic torque curves. Moreover, the anisotropy constants K 1 and K 2 have been determined from the Fourier analysis of the torque curves. The results are compared with the theoretical predictions.