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Insufficient reproducibility and measured results that are difficult to interpret are the main obstacles to widespread practical implementation of the magnetic Barkhausen noise technique as a useful non-destructive tool. This work gives a clear experimental proof that precise control of the surface magnetic field stabilizes the subsurface Barkhausen noise readout with respect to the magnetizing yoke lift-off. The surface magnetic fields above the sample were measured at two different distances by Hall sensors; the real sample field was obtained by linear extrapolation of these surface field waveforms to the sample face. This extrapolated field waveform was then adjusted to the standard triangular/sinusoidal shapes with a multi-parameter digital feedback procedure. The Barkhausen noise signal was measured locally with a bobbin coil placed on the same surface area where the magnetic field was measured. [ABSTRACT FROM AUTHOR]

Abstract: Cubic perovskite SrTi1−x Mn x O3 nanopowders with x = 0–0.5, which is much higher than the conventionally believed Mn incorporation limit, and particles sizes 10–80 nm have been successfully synthesized using the citrate sol–gel method. The crystalline structure, the morphology, the chemical composition and the lattice constant behavior versus the annealing temperature and the Mn concentration have been characterized using X-ray diffraction, scanning electron microscopy and proton-induced X-ray emission techniques. Studies of Raman light scattering and the magnetic properties revealed the activation of the TO2 polar mode and the magnetic ordering effects at low temperatures. Such features are treated as possible evidence of non-d 0 Mn-driven transition to a polar phase with multiferroicity in heavily concentrated perovskite SrTi1−x Mn x O3 nanopowders. [Copyright &y& Elsevier]

We use computational and experimental methods to study d° ferromagnetism at a charge-imbalanced interface between two perovskites. In SrTi03/KTa03 superlattice calculations, the charge imbalance introduces holes in the SrTiO3 layer, inducing a d0 ferromagnetic half-metallic 2D hole gas at the interface oxygen 2p orbitals. The charge imbalance overrides doping by vacancies at realistic concentrations. Varying the constituent materials shows ferromagnetism to be a general property of hole-type d0 perovskite interfaces. Atomically sharp epitaxial d0 SrTi03/KTa03, SrTi03/KNb03, and SrTi03/NaNb03 interfaces are found to exhibit ferromagnetic hysteresis at room temperature. We suggest that the behavior is due to the high density of states and exchange coupling at the oxygen tig band in comparison with the more studied d band t2g symmetry electron gas. [ABSTRACT FROM AUTHOR]