We report on electrical bias voltage manipulation of the magnetic domain structures of patterned ferromagnetic Fe dots on a ferroelectric BaTiO3 underlayer using a scanning probe microscope technique. Piezoresponse force microscopy is used to apply local electric field on the Fe dots/BaTiO3 hybrid structure and to map the ferroelectric domain structures simultaneously. Magnetic force microscope observation also demonstrates that the magnetic domain structures of the Fe dots significantly change with the application of voltage at room temperature through the coupling between piezoelectric and magnetostrictive effects, indicating that the Fe dots/BaTiO3 hybrid structure provides a promising basis for controlling micromagnetic domain structures using electric voltage.

A variation in the magnetization and magnetic domain structures of epitaxial Fe dots on a single crystal BaTiO 3 substrate is demonstrated in association with the structural phase transition of ferroelectric BaTiO 3. The temperature dependent magnetization of Fe dots drops suddenly at 282 K and increases again at 189 K with decreasing temperature. The variations clearly correspond to the successive structural phase transitions of BaTiO 3 from tetragonal to orthorhombic phases and from orthorhombic to rhombohedral phases. After a thermal cycle between room temperature and 150 K passing through these phase transitions, the initial magnetic domain structure of Fe dots with an enclosed magnetic flux structure changes to a single-domain-like structure due to interfacial strain between Fe and BaTiO 3 arising from possible switching of c-axis orientation of BaTiO 3 substrate.

Resistive relaxation in field-induced insulator-metal transition of a (La 0.4 Pr 0.6 ) We have investigated the resistive relaxation of a (La0.4Pr0.6)1.2Sr1.8Mn2O7 single crystal, in order to examine the slow dynamics of the field-induced insulator to metal transition of bilayered manganites. The temporal profiles observed in remanent resistance follow a stretched exponential function accompanied by a slow relaxation similar to that obtained in magnetization and magnetostriction data. We demonstrate that the remanent relaxation in magnetotransport has a close relationship with magnetic relaxation that can be understood in the framework of an effective medium approximation by assuming that the first order parameter is proportional to the second order one.