Magnetic and transport properties of La0.7Ca0.3MnO3 films controlled by structural disorder

The magnetic and the transport properties of an amorphous, a partially amorphous and a lattice-strained crystalline La0.7Ca0.3MnO3 film have been investigated. It was shown that the amorphous film exhibited Pauli paramagnetism with a, small ferromagnetic contribution provided by the interfacial crystalline inclusions. A crystalline film with nano-scale amorphous inclusions demonstrates a superposition of the ferromagnetic (corresponding to the crystalline matrix) and the superparamagnetic (corresponding to the amorphous inclusions) contributions to the magnetization. The fitted average size of the superparamagnetic particles, obtained by using a Langevin function, is completely coincident with the size of amorphous clusters represented by high-resolution electron-microscopy images. The percolating nature of the metal-insulator transition is demonstrated for the lattice-strained crystalline film.