Small-Angle Neutron Scattering Study on Ferromagnetic Correlation in (La,Tb)_2/3Ca_1/3MnO₃

Abstract

In order to make clear a correlation between mesoscopic ferromagnetic cluster and the colossal magnetoresistance in perovskite based manganites, the systems (La_1-xTb_x)_2/3Ca_1/3MnO₃ with x = 0.1 and 0.3 have been studied by small-angle neutron scattering technique. We investigated the property of mesoscopic ferromagnetic (short range ordered) cluster under the various magnetic fields and temperatures. In the sample of x = 0.3, a large number of short range ordered cluster is created below T = 150 K and persists in the two-phase coexistence state down to 8 K. The short range ordered clusters merge into single ferromagnetic domains with applying magnetic field of H = 5 T, resulting in the drop of resistivity of the order of 10⁴. According to our model calculation, we found that roughly 50% of the system remained short range ordered phase at T = 8 K and H = 0 T. The fractional volume of the short range order phase decreased to 18% with applying magnetic field up to H = 1 T.