Magnetoelastic Coupling La0.7Ca0.3MnO3//BaTiO3 Ultra-Thin Films

Aurora Alberca (Consejo Superior de Investigaciones Científicas and Universidad Complutense Madrid, Spain)

Multiferroic heterostructures combining ferromagnets and ferroelectric materials play a key role in Spintronics for their applications in the design of novel devices [1-3]. La0.7Ca0.3MnO3 (LCMO) optimally doped epitaxial ?lms were grown on ferroelectric BaTiO3 (BTO) substrates. Electronic transport (magnetoresistance and electroresistance) and magnetic properties showed important anomalies in the temperature interval between 60 and 150 K, below the metal-insulator transition. Hysteresis loops display extremely unusual features: after switching at coercivity, the magnetization overshoots the eventual high-?eld value, so called Matteucci-cycles [4]. We study with x-ray diffraction the complex strain distribution in the ?lm caused by the substrate. Scanning probe microscopy reveals changes in BTO surface morphology at low temperature. LCMO thickness is a critical factor: 120-A-thick ?lms showed large anomalies sensitive to electric poling of the BTO, whereas the behavior of 150-A-thick ?lms is closer to that of the reference LCMO samples grown on SrTiO3 [5]. Based on magnetic depth profiles from Polarized Neutron Reflectometry, magnetic anisotropy from Ferromagnetic Resonance, and a magneto-elastic anisotropy model, the following picture is proposed: through inhomogeneous strain and electric polarization effects, the ferroelectric substrate induces an inhomogenous spin distribution in the magnetic layer, compatible with the magnetic granular behavior seen in magnetism and electronic transport. This inhomogeneous strain results in the coexistence of two magnetic moment populations: antiferromagnetic patches interspersed within ferromagnetic regions. Substrate poling effects and magnetoelectric coupling are also investigated.

[1] C. A. F. Vaz and C. H. Ahn, in Ferroelectrics-Physical Effects, edited by Mickaël Lallart (InTech, 2011), p. 329. [2] H. Lu, T. A. George, Y. Wang, I. Ketsman, J. D. Burton, C. W. Bark, S. Ryu, D. J. Kim, J. Wang, C. Binek, P. A. Dowben, A. Sokolov, C. B. Eom, E. Y. Tsymbal, and A. Gruverman, Appl. Phys. Lett. 100, 232904 (2012). [3] W. Eerestein, N. D. Mathur, and J. F. Scott, Nature 442, 759 (2006). [4] A. Alberca, N. M. Nemes, F. J. Mompean, N. Biskup, A. de Andres, C. Munuera, J. Tornos, C. Leon, A. Hernando, P. Ferrer, G. R. Castro, J. Santamaria, and M. Garcia-Hernandez, Phys. Rev. B 84, 134402 (2011) [5] A. Alberca, C. Munuera, J. Tornos, F. J. Mompean, N. Biskup, A. Ruiz, N. M. Nemes, A. de Andres, C. León, J. Santamaría, and M. García-Hernández, Phys. Rev. B 86, 144416 (2012)

Back to Seminar Home Page

Last modified 20-May-2013 by website owner: NCNR (attn: )