No abstract

A sensitive field- and frequency-dependent magnetoimpedance (MI) has been observed in nanocrystalline Fe73.5Cu1Nb3Si13.5B9 ribbons. A maximum value for the MI ration ΔZ/Z=[Z(H)−Z(Hmax)]/Z(Hmax), of more than 400% was obtained in these nanocrystalline ribbons (annealed for 3–5 h at 550 °C). A peak in the field dependence of the MI ratio ΔZ/Z was observed in nanocrystalline samples, but not in the as-quenched amorphous samples. The sensitivity attained a value larger than 60% Oe−1 in the field range 3–7 Oe at 800 kHz for the nanocrystalline ribbons. Domain observation experiments show that the transverse domain structure observed in nanocrystalline samples is responsible for their giant MI effects, and the domain wall movements in the transverse domain pattern region are dominant during the initial magnetization processes in both longitudinal and transverse directions of the applied field. The correlation between the magnetization processes and the giant MI effects is discussed briefly based on the view of a modified skin effect.

A giant magnetoresistance effect (∼46% at 20 K under 7 T) and anomalous magnetic properties were found in a highly epitaxial double perovskite LaBaCoO (LBCO) thin film on (001) MgO. Aberration-corrected Electron Microscopy and related analytical techniques were employed to understand the nature of these unusual physical properties. The as-grown film is epitaxial with the c-axis of the LBCO structure lying in the film plane and with an interface relationship given by (100) || (001) and [001] || [100] or [010]. Orderly oxygen vacancies were observed by line profile electron energy loss spectroscopy and by atomic resolution imaging. Especially, oxygen vacancy and nanodomain structures were found to have a crucial effect on the electronic transport and magnetic properties.

No abstract