B. Sedlák

Mössbauer spectroscopy of goethite of small particle size

A series of synthetic acicular and natural goethite samples was examined by Mössbauer spectroscopy in the temperature range 5 to 290 K. From the temperature dependence of magnetic moment fluctuations the anisotropy constant has been estimated and the results have been compared with results of the magnetic measurements.

NMR spectra of57Fe in hexagonal ferrites with magnetoplumbite structure

The NMR spectra of57Fe in domains of MFe12O19 (M=Ba, Sr, Pb) were measured by spin echo technique at 4.2 K. The change of the heavy ion causes frequency shifts of lines corresponding to Fe3+ ions in 2b and 4f2 sites while leaving other lines essentially unchanged; the significant role of different Fe3+−M2+ bonding was found. The dipolar broadening of lines in BaFe12O19 caused by random and static displacement of bipyramidal Fe3+ ions from the mirror plane is calculated and the results are compared with the experiment.

57Fe NMR spectra in domain walls of hexagonal ferrites with magnetoplumbite structure

The domain wall NMR spectra of57Fe were measured on polycrystalline samples of BaFe12O19 and SrFe12O19 at 4·2 K. We have calculated the anisotropy of the hyperfine field dipolar component. The measured NMR spectra were interpreted supposing that the hyperfine field anisotropy is caused only by the dipolar field anisotropy.

Nuclear spin-lattice relaxation of60Co in ferromagnetic alloys Pt99Co1 and Pd99Co1

Nuclear spin-lattice relaxation (SLR) of60Co in the systems Pt99Co1, Pd99Co1 has been studied by very low temperature nuclear orientation technique. The thermal cycling method has been used. The difference of two orders of magnitude of Korringa constant has been found between Pt99Co1 and Pd99Co1.

Spin-2—on-line low temperature nuclear orientation facility at YASNAPP-2 complex in Jinr Dubna

The Spin-2 facility built at YASNAPP-2 experimental complex of the Joint Institute of Nuclear Research is described. The basic parameters of SPIN-2 and YASNAPP-2 are discussed.

Mössbauer study of defective goethite

The neutron irradiation influence on Mössbauer spectra of goethite is studied. The results are compared with the data obtained on small particle goethite samples and it is concluded, that the magnetic behaviour of goethite is especially influenced by the particle size.

Unusual magnetic behaviour of Mn spin in magnetic PtFe alloys: Nuclear orientation study

The low temperature nuclear orientation of54Mn in Pt99Fe1, Pt99,9Fe0.1 and Pt99,95Fe0.05 has been studied in the temperature rangé 5–60 mK and in the external magnetic field range 0–9 T. A considerable noncollinearity of Mn magnetic moments with respect to Bext has been found even at rather high Bext.

Nuclear orientation study of160Tb impurity in gadolinium single crystal

The low temperature nuclear orientation of160Tb in gadolinium single crystal has been studied in the temperature range 5–60 mK and in the external magnetic field Bext ≤9 T, applied both in the a- and c-axis directions. The obtained results indicate the noncollinearity between the Tb magnetic moments and the magnetization of the gadolinium matrix.

Nuclear orientation study of160Tb impurity in yttrium single crystal

The low temperature nuclear orientation of160Tb impurity in yttrium single crystal has been studied in the temperature range 5–60 mK and in the external magnetic field up to 9 T applied along a- or c-crystal axes. The experimental results are interpreted as a consequence of the interaction of Tb3+ ion with crystal field produced by the yttrium neighbours. A possible influence of technology used is also discussed.

Observation of Mn spin canting in PtFe alloys at low temperatures

The low-temperature nuclear orientation of 54Mn in Pt99Fe1 and Pt99.95Fe0.05 has been studied in the temperature range 12-50 mK and in the external magnetic field range 0-1.2 T. The strong temperature and external magnetic field dependence of the effective field Beff on 54Mn has been observed even in the range where the host itself is magnetically saturated. This behaviour is interpreted by noncollinearity of the Mn magnetic moments with respect to the macroscopic magnetisation direction.