Influence of substrate in all-ferromagnetic superlattices B.C. Behera a , P. Padhan a , W. Prellier b,n a Department of Physics, Indian Institute of Technology Madras, Chennai 600036, India b Laboratoire CRISMAT, CNRS UMR 6508, ENSICAEN, 6 Bd du Marechal Juin, F-14050 Caen Cedex, France article info Article history: Received 28 November 2014 Received in revised form 28 March 2015 Accepted 5 April 2015 Available online 8 April 2015 abstract The Raman scattering and magnetization of the superlattices consisting of ultrathin layer of two metal- like ferromagnets La 0.7 Sr 0.3 MnO 3 (LSMO) and SrRuO 3 (SRO) grown on (001)-oriented LaAlO 3 (LAO) and SrTiO 3 (STO) substrates, were studied. The Raman spectrum of LAO/[1-u.c. LSMO/2-u.c. SRO] x60 super- lattice shows modes which are shifted towards higher frequencies relative to that of LAO/[2-u.c. SRO/1-u. c. LSMO] x60 superlattice. However, the Raman spectra of these superlattices indicate the presence of orthorhombic structures of LSMO and SRO for both stacking orders. The STO/[1-u.c. LSMO/2-u.c. SRO] x60 superlattices exhibit Curie temperature (T C ) at 270 K and Neel temperature (TN) at 140 K. Surpris- ingly, T C of superlattice on LAO grown simultaneously with STO reduces to 209 K for in-plane magnetic field and to 99 K for out-plane field. But for the reverse stacking grown on LAO the T C increases to 121 and 218 K for in-plane and out-of-plane orientation of field, respectively. The superlattices grown on LAO do not show any signature of T N . Our result clearly indicates the influence of substrate induced stress and stacking order on exchange coupling between the LSMO and SRO in the superlattices, providing a useful tool towards tailoring the magnetic properties of heterostructures. & 2015 Elsevier B.V. All rights reserved. The superlattice consisting of ferromagnetic constituents La 0.7 Sr 0.3 MnO 3 (LSMO) and SrRuO 3 (SRO) exhibits several func- tionalities like antiferromagnetic coupling [1–4], magnetocaloric effect [5,6], magnetoresistance [7] etc.. Though there are several explanations for these physical properties, a detailed article re- ports that these physical properties are controlled by the structure of LSMO [3]. The LSMO can be stabilized in rhombohedral [8], orthorhombic [3,9] and mixture of both phases. The electronic and magnetic properties observed in La 1 x Sr x MnO 3 compounds are strongly controlled by the Sr-substitution [10–14]. The chemical doping similar to hydrostatic pressure, induces the local lattice distortions in bulk manganite leading to the change in bond lengths and/or angles, and thus modified the crystal structures, electronic and magnetic properties. In case of thin films of LSMO, additional source of lattice distortion is the substrate-induced strain, which is also an effective tool to tailor the electron–lattice coupling and the magnetic properties. For example, Boschker et al. [9] have observed an orthorhombic crystal structure of LSMO films grown on (LaAlO 3 ) 0.3 -(Sr 2 AlTaO 6 ) 0.7 substrate. Yang et al. [15] have observed the decrease in the saturation magnetization, and mag- netoresistance with the increase in the tensile tetragonal distor- tions of the LSMO thin film. Similarly, Tsui et al. found a magnetic anisotropy, and that Curie temperature of LSMO thin films is robust with lattice strain [16]. On the other hand, the magnetic properties of SRO and orthorhombic structure are also sensitive to the substrate-induced strain [17]. Here, we have explored the epitaxial superlattices consisting of ultrathin layer of LSMO (1 unit cell (u.c.)) and SRO (2 u.c.) grown on (001)-oriented LaAlO 3 (LAO) and SrTiO 3 (STO) substrates using pulsed laser deposition techni- que. The crystal structure, electronic structure and magnetic properties of these superlattices with both stacking order are presented in this articles. Multitarget pulsed laser deposition with a KrF excimer laser (λ ¼248 nm) has been used for the synthesis of thin films and superlattice structures. The details of the deposition process are described in our previous articles [1–3]. The deposition rate for SRO and LSMO are  0.73 Å/pulse. The superlattices comprising of 60 time repetitions of [1-u.c. LSMO/2-u.c. SRO] or [2-u.c. SRO/1-u.c. LSMO] bilayers were grown simultaneously on the (001)-oriented LAO and STO substrates. The structural characterizations of the superlattices were performed by using x-ray diffraction. The Ra- man spectra were recorded on a Jobin-Yvon LabRAM HR800UV spectrometer instrument equipped with highly efficient thermo- electrically cooled charge coupled device (CCD) [3]. The magnetic properties measurements were carried out using a super- conducting quantum interface device based magnetometer (Quantum Design MPMS-5). The magnetic field cooled tempera- ture dependent magnetization (M) measurement is performed in the presence of 0.1 T external magnetic field (H) along the in-plane and out-of-plane directions of (001) oriented LAO and STO Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jmmm Journal of Magnetism and Magnetic Materials http://dx.doi.org/10.1016/j.jmmm.2015.04.018 0304-8853/& 2015 Elsevier B.V. All rights reserved. n Corresponding author. Fax: þ33 231951600. E-mail address: wilfrid.prellier@ensicaen.fr (W. Prellier). Journal of Magnetism and Magnetic Materials 388 (2015) 22–27