Superlattices of Metallic Ferromagnetic Oxides: Interface Antiferromagnetic Coupling Effect Bhaskar Chandra Behera1, Venkata Ravindra A1, Prahallad Padhan1*, Wilfried Prellier2 1 2 Department of Physics, Indian Institute of Technology Madras, Chennai-600036, India Laboratoire CRISMAT, CNRS UMR 6508, ENSICAEN, 6 Bd du Marechal Juin, F-14050 Caen Cedex, France * Corresponding author’s e-mail: [email protected] Abstract Raman spectra and x-ray diffraction of the superlattices consisting of La0.7Sr0.3MnO3 (LSMO) and SrRuO3 (SRO) reveal orthorhombic structure of spacer layer LSMO and the presence of in-plane compressive strain, respectively. Magnetic measurements reveal enhanced coercivity, reduced magnetization, and switching of magnetic coupling with the magnetic field orientations. These magnetic properties are explained by the observed orthorhombic structure of spacer LSMO in Raman scattering. Keywords: Superlattice, Pulsed laser deposition, antiferromagnetic coupling, orthorhombic structures. Introduction The multilayers of two metallic ferromagnetic oxides LSMO and SRO exhibit several interesting magnetic properties such as exchange bias effect, inverted hysteresis loop, antiferromagnetic coupling switches to ferromagnetic coupling by changing the orientation of field etc. [1, 2]. So far, the attention has been mainly on the (001)-oriented LSMO/SRO superlattices, probably due to the simplicity of growth. However, the enhancement of magnetic properties observed for the (110) orientation LSMO and SRO thin films compared to (001) orientation due to the less crystal deformation, the more compact layer stacking therefore stronger interlayer spin-spin interaction, the faster and anisotropic relaxed unit cells, and the quenching of polar discontinuity [3, 4]. We have grown (110) oriented SRO/LSMO superlattices using multi-target pulsed laser deposition technique and studied their crystal and electronic structures and magnetic properties. Results and Discussions The x-ray diffraction patterns show the several satellite reflections apart from the substrate (110) STO peak confirms the long range periodicity of the superlattice structure with good crystallinity, shown in Figure 1. The observed out-of-plane lattice parameter of these superlattice is relatively larger compared to the bulk SRO value, indicating the presence of in-plane compressive strain due to the lattice mismatch of STO with bottom layer SRO. Raman spectra (not shown here) of these superlattices show the orthorhombic structure rather than expected rhombohedral structure for less than 4 u.c. thick LSMO spacer. Fig1: The -2 x-ray diffraction profiles and simulated spectra of (a) (110)STO/[14-u.c. SRO/2-u.c. LSMO]x15 and (b) (110)STO/[14-u.c. SRO/4-u.c. LSMO]x15 superlattices. The (110) Bragg’s reflection of STO as well as the satellite peaks are indicated. The temperature dependent magnetization curves M(T) show the in-plane antiferromagnetic coupling and out-of-plane ferromagnetic coupling between the SRO and LSMO layers of these superlattices below 160 K, the Tc of SRO. The field dependent magnetization curves (not shown here) measured at 10 K reveal the enhanced coercivity, reduced magnetization. These magnetic properties changes because of the observed orthorhombic structure of spacer LSMO layer in SRO/LSMO superlattice from the Raman scattering. Figure 2: Temperature dependent 0.1 T field cooled (a) inplane magnetization and (b) out-of-plane magnetization of the superlattices with n = 2 and 4. References  P. Padhan, W. Prellier, and R. C. Budhani, Appl. Phys. Lett. 88, (2006) 192509.  M. Ziese, I. Vrejoiu, and D. Hesse, Appl. Phys. Lett. 97, (2010) 052504.  I. C. Infante, F. Sanchez, J. Fontcuberta, M. Wojcik, E. Jedrika, S. Estrade, F. Peiro, J. Arbiol, V. Laukhin, and J. P. Espinos, Phys. Rev. B76, (2007) 224415.  J. X. Ma, X. F. Liu, T. Lin, G. Y. Gao, J.-P. Zhang, W. B. Wu, X. G. Li, and J. Shi, Phys. Rev. B79, (2009) 74424.