D. A. Mota

Magnetoelastic Coupling and Domain Reconstruction in La0.7Sr0.3MnO3 Thin Films Epitaxially Grown on SrTiO3

D. A. MotaIFIMUP 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

OUTLINE

Motivation and aim

LSMO thin films processing

Results and discussion

Summary and future work

Acknowledgments


MOTIVATION


Why perovskites?

Manganites

MOTIVATION


strain

lattice mismatch

Mn-O bond lenghtsMn-O-Mn bond angles

StructureTransportMagnetic

strongly dependent

Substrate properties SrTiO3

STO antiferrodistortive phase transition at T= 105 K

MOTIVATION – LSMO RESULTS


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 TiO6 octahedra couple to the MnO6 ones, inducing both static and dynamic changes in their configuration. The static effect appears only below TSTO 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)

La0.53Sr0.47MnO3; 11 uc; STO (100).

MOTIVATION – LSMO RESULTS


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)

La0.7Sr0.3MnO3; 26 – 220 nm; STO (001).

OPEN QUESTIONS AND AIM OF THIS WORK


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.

RESULTS AND DISCUSSION


D. A. Mota et al. in preparation






Figure. HRTEM picture of a cross-sectional sample of 330 nm LSMO thin film deposited on STO substrate


SUMMARY AND FUTURE WORK


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 TSTO yields rotations of MnO6 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 TSTO.

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

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D. A. Mota