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1.
Rev Sci Instrum ; 81(4): 043701, 2010 Apr.
Article in English | MEDLINE | ID: mdl-20441339

ABSTRACT

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).

2.
Phys Rev Lett ; 93(22): 227202, 2004 Nov 26.
Article in English | MEDLINE | ID: mdl-15601112

ABSTRACT

The magnetic and electrical properties of high-quality single crystals of A-site disordered (solid solution) Ln0.5Ba0.5MnO3 are investigated near the phase boundary between the spin-glass insulator and colossal-magnetoresistive ferromagnetic metal, locating near Ln=Sm. The temperature dependence of the ac susceptibility and the x-ray diffuse scattering of Eu0.5Ba0.5MnO3 are analyzed in detail. The uniformity of the random potential perturbation in Ln0.5Ba0.5MnO3 crystals with a small bandwidth yields, rather than the phase separation, an homogeneous short ranged charge or orbital order which gives rise to a nearly atomic spin-glass state. Remarkably, this microscopically disordered "charge-exchange-glass" state alone is able to bring forth the colossal magnetoresistance.

3.
Phys Rev Lett ; 90(17): 177203, 2003 May 02.
Article in English | MEDLINE | ID: mdl-12786099

ABSTRACT

The orbital-charge-spin ordering phase diagram for half-doped perovskites Ln(1/2)Ba(1/2)MnO3 (Ln = rare earth) with ordered Ln/Ba cations has been investigated comparatively with that of the Ln/Ba solid-solution analogs. A large modification of the phase diagram is observed upon the A-site disordering near the original bicritical point between the charge-orbital ordering and ferromagnetic metallic phases. The random potential by quenched disorder inherent in the A-site solid solution is found to suppress the respective long-range orders and gives rise to the colossal magnetoresistive state.

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