#################################################### # Karapetrova Jenia # requesting 6 days, at minimum=5 days # beamline 33BM, Investigating the strain state and lateral crystallinity in LaNiO3 films and superlattices # instrument 33BM-C fourc #################################################### # leo:~web33/beamtime-requests/req01277.txt # Internal Beam Time Request #1277 # created Tue May 05 12:09:09 -0500 2009 #################################################### apsrun: 2009-01 beamline: 33BM collaboration: No collaborator_Jenia: ON contact: jenia@anl.gov days: 6 description: Interfaces between two complex oxides can exhibit properties not found in the adjacent compounds, leading to tremendous interest in oxide interfaces as a means to stabilize electronic states not found in pure thin films or bulk crystals. However, the role of structural properties - such as strain, crystalline quality and long-range ordering of oxygen vacancies and octahedra rotations - in stabilizing interfacial states is less understood. We seek to investigate the strain state and lateral crystallinity in LaNiO3 (LNO) films and superlattices. LNO has the potential to improve a array of technologies from electrodes for ferroelectrics, spintronics as a ferromagnetic semiconductor in the La2NiMnO6 double perovskite,[1] and even predictions of superconductivity in LNO-based superlattices.[2] However, detailed accounts of the structural properties of thin layers of LNO, when strained and confined between other perovskite oxides, are lacking. We will investigate the structural properties of LNO films and LNO/manganite superlattices grown on SrTiO3 and LSAT substrates via ozone-assisted molecular beam epitaxy. Measurements of these samples using commercial diffractometers have confirmed that the superlattices are strained, with excellent out-of-plane crystallinity and chemically abrupt interfaces.[3] On Sector 33-BM, we will perform temperature dependent, specular and grazing incidence diffraction, requiring the use of the displex. Through these measurements, we will determine how the LNO films and superlattices accommodate the substrate-induced strain and how these structural modifications in turn affect the magnetic and electronic properties. Scientific Justification: We will determine the depth-dependence of the strain state, the exact composition of the superlattice structures, and explore in-plane charge ordering and coherent rotations of the oxygen octahedra through mesh scans near (H K ) peaks. These measurements will address the following scientific issues of interest to the general complex oxide community: 1) Are rotations of the oxygen octahedra present in strained LNO, as in the bulk? If present, how are these rotations affected by the substrate lattice parameters and film thickness? 2) How do errors in the desired superlattice structure (disorder) affect the magnetic properties of (LaNiO3)1/(LaMnO3)1 (111) superlattices (equivalent to ordered La2MnNiO6 double perovskites)? Can we enhance the Curie temperature of La2MnNiO6 by removing the disorder from the transition metal site? 3) Is charge disproportionation present in thin, strained layers of LaNiO3, as in bulk insulating nickelates?[4] Experiment: We propose to perform (0 0 L) and (H K ) scans on a series of LNO films and (LNO)/(SrMnO3) and (LNO)/(LaMnO3) superlattices. The (0 0 L) scans will be measured as a function of temperature from 150 – 350 K, requiring the use of a displex. Rocking curves will be measured at the (0 0 2) condition to look for evidence of microtwinning.[5] The (0 0 L) scans will be modeled to determine the composition and interfacial roughness of the superlattices. The (H K ) mesh scans will allow us to exam the strain state and in-plane crystallinity of the samples. Additionally, the mesh scans will allow us to determine if charge ordering is present in the films. [1] H. Z. Guo, et al., Phys. Rev. B. 77, 174423 (2008). [2] J. Chaloupka and G. Khaliullin, Phys. Rev. Lett. 100, 016404 (2008). [3] S. J. May, T. S. Santos, and A. Bhattacharya, Phys. Rev. B. 79, 115127 (2009). [4] J. L. Garcia-Munoz et al., Phys. Rev. B. 79, 134432 (2009). [5] U. Gebhart, et al., Phys. Rev. Lett. 98, 096101 (2007). equipment_required: experiment: Investigating the strain state and lateral crystallinity in LaNiO3 films and superlattices foreign_nationals: hazards: instrument: 33BM-C fourc instrument_other: minimumdays: 5 name: Karapetrova Jenia nonmembers: Steven J. May, Anand Bhattacharya, Philip J. Ryan submit: Submit unacceptable_dates: June 19 – 21 July 11, 18, 19 August 1 - 22 z34ID_details: #REMOTE_HOST: svo.xor.aps.anl.gov #REMOTE_ADDR: 164.54.124.13 #CONTENT_LENGTH: 4519 #HTTP_REFERER: http://www.aps.anl.gov/Sectors/33_34/admin/unireq.html #HTTP_USER_AGENT: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.0.5) Gecko/2008120122 Firefox/3.0.5 (.NET CLR 3.5.30729)