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Condensed Matter Seminars

ics Condensed Matter
Friday, November 9, 2012
2:30 PM
Physics Building, Room 313
Note special date.
Note special time.
Masa Matsuda [Host: Seunghun Lee]
Oak Ridge National Laboratory
"Spin-lattice coupling and anomalous magnetic excitations in the triangular lattice antiferromagnet Ag2CrO2"
Spin-lattice coupling plays an important role in selecting the ground state in the geometrically frustrated magnets, since a small amount of structural distortion is sufficient to lift the ground state degeneracy and stabilize a long-range magnetic order. Ag2CrO2 consists of insulating triangular lattice planes of CrO2 (Cr3+ ion with S=3/2), which are separated by the metallic Ag2 layers. Interestingly, the electric transport in the Ag2 layer is strongly affected by the magnetism in the CrO2 layer. We found from their neutron diffraction experiments that a partially disordered state with 5 sublattices abruptly appears at TN=24 K, accompanied by a structural distortion [1]. The spin-lattice coupling stabilizes the anomalous state, which is expected to appear only in limited ranges of further-neighbor interactions and temperature. The nonnegligible further-neighbor interactions suggest the existence of the RKKY interaction mediated by the conduction electrons. We have also performed inelastic neutron scattering study of this material and found anomalous magnetic excitations, which cannot be explained simply by the linear spin-wave theory. The exotic behaviors in Ag2CrO2 are noteworthy. [1] M. Matsuda et al., PRB 85, 144407 (2012)

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