Colossal magnetoresistance by avoiding a ferromagnetic state in the Mott system Ca3Ru2O7.
Transport and magnetic studies of Ca3Ru2O7 for temperatures ranging from 0.4 to 56 K and magnetic fields B up to 45 T lead to strikingly different behavior when the field is applied along the different crystal axes. A ferromagnetic (FM) state with full spin polarization is achieved for the B//a axis, but colossal magnetoresistance is realized only for the B//b axis. For the B//c axis, Shubnikov-de Haas oscillations are observed and followed by a less resistive state than that for B//a. Hence, in contrast with standard colossal magnetoresistive materials, the FM phase is the least favorable for electron hopping. These properties together with highly unusual spin-charge-lattice coupling near the Mott transition (48 K) are driven by the orbital degrees of freedom.
Lin
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Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506, USA.
Zhou
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Durairaj
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Schlottmann
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Cao
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