INVESTIGADORES
WEHT Ruben Oscar
artículos
Título:
Structural Aspects of Magnetic Coupling in CaCu3Mn4O12 and CaCu3Ti4O12
Autor/es:
M. D. JOHANNES; W. E. PICKETT; R. WEHT
Revista:
MATERIALS RESEARCH SOCIETY SYMPOSIA PROCEEDINGS
Editorial:
Materials Research Society
Referencias:
Año: 2002 vol. 718 p. 25 - 33
ISSN:
0272-9172
Resumen:
Two perovskite-derived materials, CaCu3Mn4O12,
have drawn much recent interest due to their magnetoresistive,
dielectric, and mafnetoelectronic characteristics. Here we present
initial theoretical insights into each of these points, based on first
principles, density functional based calculations. Our results predict
CCMO to have a spin-asymmetric energy gap, which leads to distinct
temperature- and magnetic field-dependent changes in properties, and
helps to account for its observed negative magnetoresistivity. We have
studied CCTO primarily to gain insight into the exchange coupling in
both these compounds, where the conventional superexchange coupling
vanishes by symmetry for both nearest and next nearest Cu-Cu neighbors, a
consequence of the structure. In CCTO, it is necessary to go 5th Cu-Cu
neighbors to obstain a (superexchange) coupling that can provide the
coupling necessary to give three dimensional order. Non-superexchange
mechanisms may be necessary to describe the magnetic coupling in this
structural class.