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-assembled nanodots formed in a nonmagnetic alumina matrix, which were produced 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 found to be 2–5 nm, which is sufficient to decouple the magnetic grains. The decoupling of the grains is supported by the zero-field-cooled and field-cooled magnetization (M) data. The coercivity of the La2/3Ca1/3MnO3 nanodots has 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 200 Oe at 20 and 50 K, respectively. Above the blocking temperature, the sample is found to transform to a superparamagnetic magnetic state, resulting in the disappearance of any hysteresis in the M–H loops.