A high-speed polarizing microscope system combined with a 37 T pulse magnet has been developed. This system was applied to successfully visualize the field-induced collapse of charge-orbital ordering in a layered manganite La(1/2)Sr(3/2)MnO(4). Quantitative analyses of the obtained polarizing microscope images provided clear evidence of this transition in contrast to rather moderate changes in magnetization and magnetoresistance. The ability of this system to carry out quantitative analysis was further tested through the observation of Faraday rotation in a Tb(3)Ga(5)O(12) crystal. The Verdet constant determined from the polarizing images is in reasonable agreement with that in literature. Local intensity analyses of the images indicate that we can investigate magneto-optical signals within an accuracy of 0.85% in an area of 9.6 x 9.6 microm(2).
We have investigated temperature and magnetic-field dependence of dielectric properties in the orthorhombic GdMnO3 single crystal which is located near the phase boundary between the ferroelectric/spiral-antiferromagnetic phase and the paraelectric/A-typeantiferromagnetic one. In this compound, strong phase competition between these two phases results in a unique phase diagram with large temperature and magnetic-field hystereses. Based on the phase diagram, we have successfully demonstrated the persistent and reversible phase switching between them by application of magnetic fields.
We have investigated the magnetic and dielectric properties of orthorhombic Eu 1Ày Y y MnO 3 (0 y 0:6) single crystals without the presence of the 4f magnetic moments of the rare-earth ions. In y ! 0:2, the magnetic-structure driven ferroelectricity is observed. The ferroelectric transition temperature is steeply reducing with increasing y. In y ! 0:52, two ferroelectric phases (P k a and P k c) are coexistent at low temperatures. In these phases, ferroelectricity has different origin, which is evidenced by the distinctive poling-electric-field dependence of electric polarization. Namely, the electric polarization along the c-axis (P c ) is easily saturated by a poling electric field, therefore P c is caused by the bc-spiral antiferromagnetic order. On the other hand, the electric polarization along the a-axis (P a ) is probably attributed to the collinear E-type antiferromagnetic order, because P a is unsaturated even in a poling field of 10 6 V/m.
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