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MA: Magnetismus

MA 11: Spin-Structures and Magnetic Phase Transitions II

MA 11.3: Vortrag

Montag, 27. März 2006, 15:30–15:45, HSZ 403

Spin State Transformations of a 3d Ion in the Pyramidal Environment under Lattice Distortions — •Karina Lamonova, Helen Zhitlukhina, Sergei Orel, and Yurii Pashkevich — A.A. Galkin Donetsk Phystech NASU, 83114 Donetsk, Ukraine

The spin state (SS) transitions in the metal-containing pyramidal complexes originated from the crystal structure deformations are the research subject of this work. As the metal ions, we considered the transition metals with the 3d6 and 3d4 configurations. The SS transitions of the metal ions from low spin (LS, S=0) to the intermediate spin (IS, S=1) and high spin (HS, S=2) under change of the metallic ion effective charge Zeff and displacements of the oxygen ions has been investigated in the frame of crystal field approximation. The features of the SS stability have been calculated without spin-orbit interaction accounting, and then with the accounting one. Some critical points over Zeff at which an accident degeneracy of SSs have been revealed. Near these critical points, the negligible distortions can crucially influence on the SS changing. The ground SS of pyramidal Me-O complex is very sensitive to the symmetry and magnitude of the oxygen cage distortions. We probed the breathing like distortions, the displacement of the 3d-ion along Z axis, Jan-Teller like ion displacements, and the displacements like pyramidal plane corrugation. The SS diagrams in the parameter space No-dqeffective chargeNo-dq-No-dqdistortion magnitudeNo-dq have been built. It is revealed the IS ground state exists for all kind considered distortions at the corresponding choice of the Zeff value. Jan-Teller distortions stabilize the IS state in a wide range of Zeff that consistent with experimental data on layered cobaltites.