Magnetism and electronic transport signatures of Exchange-bias in La0.75Sr0.25MnO3/LaNiO3 multilayers"

J.C. ROJAS SANCHEZ; M. GRANADA; G. LEYVA; L.B. STEREN

Conferencia; Villa Conference on Complex Oxides Heterostructures; 2009

Magnetoresistive systems have been widely studied due to their potential application in spintronics devices. In particular, the development of oxides-based devices has attracted much interest lately [1]. In a previous work, we have shown that trilayers composed of La0.75Sr0.25MnO3 (LSMO) ferromagnetic electrodes and LaNiO3 (LNO) spacers present a giant magnetoresistance effect. [2] In the present work we show that the magnetic properties of theses structures present unexpected behaviour that makes them very interesting from a fundamental point of view. A detailed study of the magnetism of LSMO/LNO structures reveals that these multilayers exhibit an exchange-bias anisotropy in spite of the fact that LNO is a Pauli paramagnet. Bilayers and multilayers with different LNO thickness have been grown by magnetron dc sputtering on crystalline (001) SrTiO3 substrates. X-ray diffraction measurements indicate that the samples grow highly textured in the (001) direction. [3] The relative shift of the magnetization loops along the magnetic field axis measured at low temperatures and different cooling conditions is the main evidence of an exchange-bias like behaviour. Moreover, we measure different coercive fields, when measured in zero-field-cooling (ZFC) and field-cooling (FC) experiments. The FC experiments were carried out after cooling the samples from 250K to 5K with different applied fields (1kOe < H < 4kOe). The temperature dependence of the exchange bias effect has been also studied. Preliminary magneto-transport measurements, performed in the same experimental conditions will be also presented.