Magnetic properties of self-assembled nanoscale La2/3Ca1/3MnO3 particles in an alumina matrix

We have investigated the processing and properties of La2/3Ca1/3MnO3 self-a ssembled nanodots formed in a nonmagnetic alumina matrix, which were produc ed by a pulsed-laser deposition process. The size of the nanodots was found to be in the range of 10-15 nm using high-resolution transmission electron microcopy. The average interlayer separation between two dots has been fou nd to be 2-5 nm, which is sufficient to decouple the magnetic grains. The d ecoupling of the grains is supported by the zero-field-cooled and field-coo led magnetization (M) data. The coercivity of the La2/3Ca1/3MnO3 nanodots h as been measured using magnetization measurements as a function of field (H ) at different temperatures above and below the blocking temperature of the samples. The coercivity is found to vary from 600 Oe at 10 K to 400 and 20 0 Oe at 20 and 50 K, respectively. Above the blocking temperature, the samp le is found to transform to a superparamagnetic magnetic state, resulting i n the disappearance of any hysteresis in the M-H loops. (C) 2001 American I nstitute of Physics.