부산대학교 도서관

The magnetic and transport properties of anion- and cation-deficient [Nd.sub.0.52][Sr.sub.0.48]Mn[O.sub.3] films with different thicknesses, as well as of two films from this system grown on different SrTi[O.sub.3] and LaAl[O.sub.3] substrates, are studied. Below Curie temperature [T.sub.C], the films with different thicknesses exhibit phase separation: they represent magnetic clusters (drops) embedded in a nonconducting paramagnetic (at T > [T.sub.N], where TN is the Neel temperature) or antiferromagnetic (T < [T.sub.N]) matrix. The temperature dependences of the resistivity of the films are well described in terms of the polaron mechanism of conduction. In external magnetic field H = 0.01 T, the drops may reach 15 nm in size. They consist of magnetic polarons with a small radius (1-2 nm). The drops are shown to interact with each other in the films. Because of competition between drop-drop dipole interaction and the magnetic energy, the drops disintegrate into droplets with a size comparable to that of a magnetic polaron in a field of 1 T. An explanation is given for the discrepancy between our results and the frequently observed growth of the drops with a rise in the external magnetic field. As the film gets thicker, the fraction of the ferromagnetic phase grows with thickness nonlinearly. In the film grown on SrTi[O.sub.3] (compressed by 0.9%), the characteristic Neel and Curie temperatures are lower than in the film grown on LaAl[O.sub.3]. The diameters of ferromagnetic drops (both maximal at H = 0.01 T and minimal at H = 1 T) turn out to be roughly the same as in the films with different thicknesses. DOI: 10.1134/S1063784211100100
INTRODUCTION The available set of experimental data on the evolution of the magnetic-transport and magnetic characteristics of doped manganites away from the temperatures of magnetic and structural transitions in the [...]