Dresden 2006 – scientific programme

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MA: Magnetismus

MA 24: Magnetic Thin Films III

MA 24.1: Talk

Thursday, March 30, 2006, 10:15–10:30, HSZ 03

Spin-polarized grain boundary transport in reversibly strained La_0.7Sr_0.3MnO₃ polycrystalline films — •Gangineni Ramesh Babu, K. Dörr, K. Nenkov, N. Kozlova, K.-H. Müller, and L. Schultz — IFW Dresden, PF 270116, D-01171 Dresden, Germany

La_0.7Sr_0.3MnO₃ (LSMO) is a ferromagnetic manganese oxide with half-metal like character, with a ferromagnetic Curie temperature T_C of about 370 K. The high spin polarization has been demonstrated using tunnelling experiments in epitaxial trilayer structures of LSMO with SrTiO₃ (STO) insulating barrier, where a huge value of tunnelling magnetoresistance of TMR = 1800 % at low temperature has been found recently [1]. Polycrystalline LSMO films contain a network of many grain boundaries typically acting as tunnel barriers. Thus, they also show large TMR at low temperature. In this work, we have prepared polycrystalline films of LSMO on monocrystalline actuator platelets of Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃(001) (PMN-PT) [2] in order to study the grain boundary tunnelling transport in dependence on controlled in-plane strain. Reversible strain by up to 0.15 % has been applied to the films using the inverse piezoelectric effect of the substrates. Temperature-dependent resistance and magnetoresistance data in dependence on applied strain will be discussed with regard to the microstructure of the films. Further, it has been tried to prepare epitaxial trilayer tunnel junctions on PMN-PT(001) and measure their current-voltage characteristics under various strain states.
This work is supported by DFG, FOR 520.
[1] Bowen M et al., Appl. Phys. lett, 82, 233 (2003)
[2] Thiele C, Dörr K et al., Appl. Phys. Lett (in press)