Magnetotransport properties and phase separation in iron substituted lanthanum-calcium manganite

Crystal and magnetic structure of iron substituted La0.7Ca0.3Mn0.5Fe0.5O3 manganite was investigated by powder neutron diffraction in the 10-300 K temperature range. It is established that the unit cell parameters at 300 K are a = 5.447(2) angstrom, b = 7.709(3) angstrom, c = 5.467(3) angstrom and they change vs. temperature with rates da/dT similar to 1.3*10(-4) angstrom*K-1, db/dT similar to 1.7*10(-4) angstrom*K-1 and dc/dT similar to 1.6*10(-4) angstrom*K-1, respectively. It was also realized the measurements of magnetization and electrical resistivity in the 5-300 K temperature range including in magnetic fields up to 1 T. Magnetic phase separation was observed. Upon the field increase the glass, T-g, and irreversibility, T-irr, temperatures decrease, while the magnetic ordering temperature, T-mo, increases. Upon the temperature increase both the residual magnetization, M-r, and coercive field, H-c, decrease. A complex frustrated magnetic state in which the long-range G-type antiferromagnetic phase coexists with the short-range ferromagnetic clusters was established. An average size of ferromagnetic clusters is D-av similar to 20 nm. An anomalous temperature behavior of electrical conductivity for La0.7Ca0.3Mn0.5Fe0.5O3 was found which confirms a transformation of various magnetic states. Different models of conduction mechanism were considered. The origin of the unusual magnetic state, the electrical conduction mechanisms, and the relationship between magnetic and electrotran-sport properties in this sample were discussed.