Magnetite single crystals with Al, Ga and Ti substitutions were measured by means of 57Fe nuclear magnetic resonance (NMR) technique. Satellite structure of NMR spectra well above the Verwey temperature was detected and analyzed to obtain information on the distribution of substituting cations on iron sublattices. It was confirmed that Al and Ti enter iron octahedral B-sites. Ga strongly prefers tetrahedral A-sites, nevertheless a low presence of Ga cations in B-sites was detected.

The temperature dependence of the O K-edge threshold has been investigated in a temperature range encompassing the Verwey transition. Both above and below T-V the O K-edge threshold changes linear with temperature whereas there is discontinuous energy shift of 13 meV at T-V. A comparison of our results to published low and high energy photoemission experiments suggests the presence of an asymmetric gap with respect to the Fermi level. This explains present fundamental differences between photoemission and infrared derived gap energies, and supports the polaronic image of the electrical conductivity of Fe3O4 above the Verwey transition temperature.

Elastic (Jahn–Teller) domains and magnetic domains in the tetragonal spinel Mn2FeO4 were studied using X-ray double-crystal topography, X-ray diffractometry and the colloid-SEM method. The Jahn–Teller domains of the measured samples are tetragonal with the [001] c-axis alternating perpendicularly (thick domains) and parallel (thin domains) with respect to the growth direction of the specimens. Boundary interfaces are of the (110) type consistent with the cubic spinel system. A complex magnetic domain structure is discussed in relation with the crystallographic orientation of the Jahn–Teller domains.

Single crystals of Bi2Sr2Ca1−xYxCu2O8+z with Y concentration between 0.0 and 0.51 have been prepared by the travelling-solvent-floating-zone method. The composition, structure, superconductivity and critical current density of this system were investigated. Evidence is found that yttrium has substituted the Ca ions, which leads to a linear decrease of c-axis length. However, a second phase is also found for high Y concentration (x>0.2) of which the c-axis length is nearly independent of the composition. The substitution of Ca by Y enhances Tc up to 95.3 K at x=0.2, but depresses Tc sharply for x>0.2. The temperature dependence of Jc(T) shows a kink at about 25 K (± 3 K) for x<0.5, indicating that there exist always two different pinning regimes in the Y-substituted single crystals.

The room-temperature spin wave spectrum in MnFe2O4 has been investigated by means of inelastic neutron scattering using the time-of-flight technique. The acoustical branch could be obtained in the [100]- and the [110]-directions up to nearly the Brillouin zone boundary. Values for the effective exchange parameters JAB and JBB have been derived. In both symmetry directions some low lying phonon branches could also be observed.

The room-temperature spin wave spectrum has been investigated in Mn1.7Fe1.3O4 by means of inelastic neutron scattering. The acoustical branch could be obtained in the symmetry directions. Values for the effective exchange parameters JAR and JRR have been derived. Some acoustical phonon branches could also be observed and the elastic constants C44 and (C11 – C12) were estimated.

Measurements of the Hall effect in manganese ferrites are reported. The temperature dependence of the Hall mobility gives no evidence of any need for band-conduction.