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Emission and transmission Mössbauer studies of La0.8Sr0.2CoO3-δ perovskites doped with ∼0.02 stoichiometric units of oxygen vacancy or 2.5% iron corroborate the occurrence of electronic phase separation in these systems. The effect of the small perturbation of the CoO3 sublattice with either iron ions or oxygen vacancies on the bulk magnetization as well as on the Mössbauer spectra is in good agreement with the double exchange based cluster model. The magnetoresistance does not show any peak near the Curie temperature, but reaches -84% in a field of 7.5 T at T = 8 K. Below TC ≈ 180 K the Mössbauer spectra distinctly include the contribution from paramagnetic and ferromagnetic regions, providing direct evidence for phase separation. No contribution to the spectra from Fe4+ ions can be observed, which is an unambiguous evidence that at low concentration iron (either directly doped or formed from 57Co by nuclear decay) is accommodated in the cobaltate lattice as Fe3+ ion. [ABSTRACT FROM AUTHOR]

In this paper we present 57Co emission Mössbauer and AC magnetic susceptibility studies of La0.8Sr0.2CoO3- δ perovskite. The observed coexistence of paramagnetic and magnetic subspectra in the 57Co emission Mössbauer spectra, as well as the difference of their isomer shifts support the existence of electronic phase separation in this perovskite, in good agreement with the double exchange based cluster model. [ABSTRACT FROM AUTHOR]

Eu0.8Sr0.2Fe x Co1− x O3− z CMR perovskites with different iron concentrations ( x = 0, 0.025, 0.075, 0.15, 0.3) were investigated by X-ray diffraction, AC magnetic susceptibility, magnetotransport, as well as 57Fe and 151Eu Mössbauer spectrometry. The valence state of europium ions was found to be trivalent, independently of the iron concentration. 57Fe Mössbauer spectra and magnetic susceptibility of the investigated perovskites presented complementary results for the magnetic transitions. [ABSTRACT FROM AUTHOR]

La0.8Sr0.257Fe0.05Co0.95O3-d perovskite is investigated by 57Fe transmission and emission Mössbauer spectroscopy, X-ray diffraction, AC magnetic susceptibility and magnetotransport measurements. Temperature dependence of the 57Fe Mössbauer isomer shift, quadrupole splitting, magnetic hyperfine field, line broadening, and relative spectral area is presented in a detailed manner for La0.8Sr0.257Fe0.05Co0.95O3-d . The oxidation state of iron is determined to be Fe3+, and the presence of preferential electronic charge compensation Fe3+ ? Fe4+ over that of Co3+ ? Co4+ is excluded. Relaxation of iron magnetic moments reflected by the 57Fe Mössbauer spectra of La0.8Sr0.257Fe0.05Co0.95O3-d are interpreted as evidence for the existence of superparamagnetic like Co clusters and a corresponding cluster glass magnetic phase formed below T ˜65 K. [ABSTRACT FROM AUTHOR]

Different factors have been studied that influence the residual resistivity analysis of gallium. A proper method to separate the impurity contribution from the measured resistivity has been established and the suitable experimental apparatuses and procedures have been developed. The empirical correlation between the impurity contribution of resistivity and the integral impurity concentration of gallium metal has been studied on the basis of data obtained from measurements on a large number of gallium samples of various purity grades. [ABSTRACT FROM AUTHOR]

A short introduction about biomagnetism and associated instrumentation is given in the first part of the paper. The application of SQUIDs and superconducting gradiometers in clinical biomagnetic instruments is reviewed in some detail. The construction and adjustment of a third order gradiometer is described later and a magnetocardiogram is displayed to demonstrate the capability of the instrument. [ABSTRACT FROM AUTHOR]