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

Abstract

Crystal and magnetic structure of iron substituted La0.7Ca0.3Mn0.5Fe0.5O3 manganite was investigated by powder neutron diffraction in the 10–300 К temperature range. It is established that the unit cell parameters at 300 K are a = 5.447(2) Å, b = 7.709(3) Å, c = 5.467(3) Å and they change vs. temperature with rates da/dT ∼ 1.3*10–4 Å*K−1, db/dT ∼ 1.7*10–4 Å*K−1 and dc/dT ∼ 1.6*10–4 Å*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, Tg, and irreversibility, Tirr, temperatures decrease, while the magnetic ordering temperature, Tmo, increases. Upon the temperature increase both the residual magnetization, Mr, and coercive field, Hc, 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 Dav ∼ 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 electrotransport properties in this sample were discussed.