Magnetic and transport properties of La0.6Sr0.4MnO3/La0.9Sr0.1MnO3/ La0.6Sr0.4MnO3.

M. SIRENA; M. GRANADA; L. B. STEREN; J. GUIMPEL

S. C. de Bariloche

Workshop; V Latin American Workshop on Magnetism, Magnetic Materials and their Applications; 2001

In the last decade, a lot of work has been done in the study of magnetic coupling and magnetoresistance in metallic multilayers. More recently, the observation of an intrinsic "colossal" magnetoresistance effect in manganite compounds has led to an enlargement of this materials group. The scope of this work is to study magnetic and transport properties of trilayers based on manganite compounds. Thin films and trilayers have been grown by dc sputtering on MgO and SrTiO3 substrates. Films of La0.6Sr0.4MnO3 (A) and La0.9Sr0.1MnO3 (B), with thickness varying from 10nm to 300nm, have been preapared in order to study the intrinsic properties of these materials. X-ray diffraction patterns show that both series of samples grow strongly textured in the c direction perpendicular to the film surface. The similar structure and lattice parameters make these films specially attractive to build multilayers with interfaces of good quality. The temperature and magnetic field dependence of the magnetization and resistivity have been measured in these samples. La0.6Sr0.4MnO3 thin films are ferromagnetic with a Curie temperature (TCA) around room temperature. These manganites present a metal-insulator transition below TCA and exhibit colossal magnetoresistance. On the other hand, films with low Sr concentration although ferromagnetic (TCB<TCA), are insulator. Each compound preserves its general properties, even for small thicknesses (~10nm). As a consequence of reducing the film size, a depression of the Curie point is observed. A/B/A trilayers have been prepared with different A and B thicknesses (10nm< thA < 50nm and 10nm < thB< 50nm). The growth of the heterostructure has been controlled by X-ray diffraction. The magnetic coupling between A layers has been studied through magnetization and ferromagnetic resonance measuremens. A detailed analisys of the interlayer coupling has been performed at two temperatures, i.e. at room temperature, where the spacer is paramagnetic and at T=77K, where it is ferromagnetic. Transport measurements are under progress.