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We could make nano-sized columnar domains with a checkerboard pattern in inorganic spinels by harnessing the Jahn-Teller structural distortion. Transmission electron microscope images reveal that the fundamental domain structures consist of two types of long nanorods with the ~4X4X70 nm3 size, which are alternatively stacked in a way that the cross sectional and side views show checkerboard and herringbone patterns, respectively. The strain induced by the Jahn-Teller distortion is discussed to cause this peculiar self-assembled nanostructure in the coherent mixture of two spinel phases. This pure solid state self-assembly can be implemented to fabricate heterogeneous nanostructures with practical functionalities.
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Here, an intriguing glass transition in (La,Pr,Ca)MnO_3 is imaged using a variable-temperature magnetic force microscope. In contrast to the speculated spin-glass picture, our results show that the observed static magnetic configuration seen below the glass-transition temperature arises from the cooperative freezing of the first-order antiferromagnetic (charge ordered) to ferromagnetic transition. Our data also suggest that accommodation strain is important in the kinetics of the phase transition.
(Weida Wu et al., Nature Materials, 5, 881-886, 2006)
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Multiferroic materials exhibit simultaneously magnetism and ferroelectricity, and extraordinary cross-coupling phenomena between magnetism and ferroelectricity in multiferroics have been recently discovered. Examples of the cross-coupling phenomena include the reversible 180 degree polarization flipping in TbMn2O5 (N. Hur et al., Nature 2004). Soonyong Park has recently succeeded in growing large-size single crystals (up to 2 cm) of TbMn2O5 by using a flux method.
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