The structure and transport properties of Sm1-xCaxMnO3 with 0.4less than or equal toxless than or equal to0.8 were investigated. With decreasing temperature from 350 K, cooperative Jahn-Teller (JT) distortion develops, leading to the formation of a charge ordered (CO) state and anomalies in the lattice parameters and resistivities. At low temperature the magnetoresistance effect originates from the polarization of the localized t(2g) spins under the magnetic field and decreases with the increase in Ca2+ content x, whereas the stability of the CO state at the CO transition temperature T-CO strongly depends on both Ca2+ content and cooperative JT distortion. These interesting phenomena sufficiently confirm the close relationship among charge, lattice, spin, and orbital degrees of freedom. (C) 2004 American Institute of Physics.
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