1. Magnetoelastic Coupling and Domain Reconstruction in La 0.7 Sr 0.3 MnO 3 Thin Films Epitaxially Grown on SrTiO 3 D. A. Mota IFIMUP and IN-Institute of Nanoscience and Nanotechnology, Department of Physics and Astronomy, Faculty of Science of University of Porto, Rua do Campo Alegre, 687, 4169-007 Porto, Portugal NEW CHALLENGES IN THE EUROPEAN AREA: YOUNG SCIENTIST’S 1ST INTERNATIONAL BAKU FORUM 20 – 25 MAY 2013, BAKU, AZERBAIJAN

2. OUTLINE  Motivation and aim  LSMO thin films processing  Results and discussion  Summary and future work  Acknowledgments Magnetoelastic Coupling and Domain Reconstruction in La 0.7 Sr 0.3 MnO 3 Thin Films Epitaxially Grown on SrTiO 3

3. MOTIVATION Magnetoelastic Coupling and Domain Reconstruction in La 0.7 Sr 0.3 MnO 3 Thin Films Epitaxially Grown on SrTiO 3 Why perovskites? Manganites

4. MOTIVATION Magnetoelastic Coupling and Domain Reconstruction in La 0.7 Sr 0.3 MnO 3 Thin Films Epitaxially Grown on SrTiO 3 strain lattice mismatch Mn-O bond lenghts Mn-O-Mn bond angles Structure Transport Magnetic strongly dependent Substrate properties SrTiO 3 STO antiferrodistortive phase transition at T= 105 K

5. MOTIVATION – LSMO RESULTS Magnetoelastic Coupling and Domain Reconstruction in La 0.7 Sr 0.3 MnO 3 Thin Films Epitaxially Grown on SrTiO 3 Result of a coupling between the charge carriers in the film and the soft phonon in the STO, through linked oxygen octahedral motions. The motions of the TiO 6 octahedra couple to the MnO 6 ones, inducing both static and dynamic changes in their configuration. The static effect appears only below T STO and do not explain the anomalous temperature behavior of both resistivity and magnetization -> a dynamical coupling was assumed. This effect should not be observed in thicker films due to the penetration depth of the soft phonons that was estimated to be just 2-3 atomic layers. Segal et al., PRL 107, 105501 (2011)  La 0.53 Sr 0.47 MnO 3 ;  11 uc;  STO (100).

6. MOTIVATION – LSMO RESULTS Magnetoelastic Coupling and Domain Reconstruction in La 0.7 Sr 0.3 MnO 3 Thin Films Epitaxially Grown on SrTiO 3 Dynamical coupling with soft phonon assumed in an earlier work, was disproved: Since similar temperature behavior of the magnetization is also observed in thicker films. Mechanism proposed -> magnetic domain reconstruction. Pesquera et al., PRB 84, 184412 (2011)  La 0.7 Sr 0.3 MnO 3 ;  26 – 220 nm;  STO (001).

7. OPEN QUESTIONS AND AIM OF THIS WORK Magnetoelastic Coupling and Domain Reconstruction in La 0.7 Sr 0.3 MnO 3 Thin Films Epitaxially Grown on SrTiO 3  Very different mechanisms have been used to explain the temperature behavior of the magnetic and transport properties;  No quantitative analysis was presented in order to understand the results obtained in the LSMO thin films;  We aim at correlating the order parameter of the STO phase transition with the magnetic and transport properties changes occuring at 105 K;  LSMO thin films deposited onto STO(100) substrates by pulsed laser deposition with thicknesses between 20 and 330 nm.

8. RESULTS AND DISCUSSION Magnetoelastic Coupling and Domain Reconstruction in La 0.7 Sr 0.3 MnO 3 Thin Films Epitaxially Grown on SrTiO 3 D. A. Mota et al. in preparation

9. RESULTS AND DISCUSSION Magnetoelastic Coupling and Domain Reconstruction in La 0.7 Sr 0.3 MnO 3 Thin Films Epitaxially Grown on SrTiO 3 D. A. Mota et al. in preparation

10. RESULTS AND DISCUSSION Magnetoelastic Coupling and Domain Reconstruction in La 0.7 Sr 0.3 MnO 3 Thin Films Epitaxially Grown on SrTiO 3 Figure. HRTEM picture of a cross-sectional sample of 330 nm LSMO thin film deposited on STO substrate D. A. Mota et al. in preparation

11. SUMMARY AND FUTURE WORK Magnetoelastic Coupling and Domain Reconstruction in La 0.7 Sr 0.3 MnO 3 Thin Films Epitaxially Grown on SrTiO 3  This work shows how the lattice distortions associated with the STO phase transition induce changes of the physical properties of LSMO thin films ensured by an interface-mediated magnetoeloastic effect;  The increasing rotation angle below the T STO yields rotations of MnO 6 octahedra, which due to the high sensitivity to structural changes of LSMO tune Mn-intersite hopping of charge carriers and localized spin arrangements.  Above the critical thickness, formation of randomly oriented magnetic domain reconstructions, mediated by the order parameter of the STO, takes place in order to relax the increasing tension.  Future work: Study the effect of different applied magnetic fields on the magnetization above T STO.

12. Thank You!! This work was supported by the Fundação para a Ciência e Tecnologia and COMPETE/QREN/EU, through the project PTDC/CTM/099415/2008