Tunneling magnetoresistance in La0.75Sr0.25MnO3 / CaMnO3 trilayers

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

Buenos Aires, Argentina

Workshop; At the Frontiers of Condensed Matter IV; 2008

Magnetic tunnel junctions are systems of much interest due to their potential technological applications. High spin polarization of the conduction electrons in the ferromagnetic electrodes enhances the tunneling magnetoresistance (TMR) effect.  Ferromagnetic manganites are nearly  half-metallic, which makes these compounds very good candidates for developing TMR devices. There are different kinds of insulating spacers that can be used as a barrier, and the transport properties of the junctions depend strongly on the properties of the spacer material [1]. We have fabricated magnetic tunnel junctions composed of La0.75Sr0.25MnO3 (LSMO) electrodes and CaMnO3 (CMO) spacers. LSMO films are ferromagnetic and metallic below room temperature and CMO is an antiferromagnetic insulator, presenting weak-ferromagnetism below $T_N sim $120 K in bulk. The trilayers where deposited by dc sputtering on STO substrates, and X-ray diffraction patterns indicate that they grow textured on the substrate´s (001) direction [2]. The junctions where defined by optical lithography with ion-etching. In this work, we present a study of the magneto-transport properties of a 100$mu$m diameter junction. The sample presents an insulating behavior over all the temperature range, indicating the barrier has no pinholes. We have measured TMR at low temperature and characterized the behavior of the barrier at different temperatures by analyzing I-V curves. [1] M. Bibes and A. Barthélémy IEEE Transactions on Electron Devices 54, 1003 (2007).  [3] M. Granada, M. Sirena, L. B. Steren and A. G. Leyva, Physica B 354, 113 (2004).