[JRG Seminar] Superexchange Interaction in Orthorhombic Perovskite Oxides:
* SPEAKERS
Name
Affiliation
E-mail
Dr. Beom Hyun Kim
POSTECH
Prof. Ki-Seok KIM (APCTP) kimks(at)apctp.org
* HOST(Applicant)
Name
Affiliation
E-mail
-
* DATE / TIME
2009-03-18, 2pm
* PLACE
512 Hogil Memorial Bldg., APCTP Headquarters,
* ABSTRACT
The perovskite oxides (AMO3) which consist of Mn3+ or Cu2+ show the strong interplay between the orbital, lattice, and spin degrees of freedom. Due to the Jahn-Teller (JT) effect, the doubly degenerate eg orbitals are split and the C-type orbital ordering occurs. Different hopping nature of the orbital ordered system induces the A-type antiferromagnetism (A-AFM) in LaMnO3 and TeCuO3. The mismatch of A-O and M-O bond lengths causes the oxides to have the GdFeO3 type distortion in which the MO6 octahedra are tilted cooperatively. Decreasing the A-site ionic size, the M-O-M angle decreases from 180o to 90o and the magnetic interaction of the A-AFM is reduced. Moreover, the magnetic transition occurs from the A-type to E-type through the spiral ordering in the large tilting cases in RMnO3 (R: rare-earth element) systems and from the AFM to ferromagnetic in Se1-xTexCuO3 systems.
In this study, we have set the microscopic Hamiltonian for the perovskite oxides, where the structure is deformed by the GdFeO3-type octahedral tilting and the JT distortion. Solving this microscopic model, we have examined the magnetic interaction of RMnO3 and Se1-xTexCuO3 systems. We have studied the nearest neighbor and next nearest neighbor interactions for a series of RMnO3 systems systematically by varying the tilting angle, distortion angle, and the JT splitting. For Se1-xTexCuO3, we have shown that the C-type orbital order leads to the A-type magnetic ground state, and that the sp hybridization between oxygen and Se or Te plays a key r
