Magnetoelectric phenomena in manganites R0.6Ca0.4MnO3 (R = pr, nd) with charge ordering suppressed by a magnetic fieldстатья
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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация:A change in electric polarization (up to 300 mu C/m(2)) upon magnetic-field suppression of a charge-ordered anti ferromagnetic state upon a transition to the ferromagnetic conducting phase (H-cr similar to 65-80 kOe at 4.2 K) is discovered in Pr0.6Ca0.4MnO3 and Nd0.6Ca0.4MnO3 single crystals. The transition is also accompanied by a jump in magnetization and magnetostriction. The dependence of the induced polarization sign on the polarity of the electric field in which the sample was preliminarily cooled indicates the existence of spontaneous electric polarization. The effect is the strongest in Nd0.6Ca0.4MnO3 and is weaker by a factor of 5-10 in Pr0.6Ca0.4MnO3, for which the tolerance factor is higher. The observed effect may be associated with recently predicted noncentrosymmetric structures in doped manganites with x similar to 0.5 (see D.V. Efremov, J. van den Brink, and D.I. Khomskii, Nature Materials 3, 853 (2004)), in which e(g) electrons are not localized upon charge and orbital ordering at one manganese ion, but are distributed among neighboring ions, thus forming an ordered polar dimer structure.