Spontaneous cationic ordering in chemical-solution-grown La 2 CoMnO 6 double perovskite thin films

摘要

Double perovskite oxides are of interest because of their electric, magnetic, and elastic properties; however, these properties are strongly dependent on the ordered arrangement of cations in the double perovskite structure.Therefore, many efforts have been made to improve the level of cationic ordering to obtain optimal properties while suppressing antisite defect formation.Here, epitaxial double perovskite La2CoMnO6 thin films were grown on top of (001)-STO oriented substrates by a polymer-assisted deposition chemical solution approach.Confirmation of the achievement of full Co/Mn cationic ordering was found by scanning transmission electron microscopy (STEM) measurements; EELS maps indicated the ordered occupancy of BB sites by Co/Mn cations.As a result, optimal magnetic properties (Msat6B/f.u.and Tc230K) are obtained.We show that the slow growth rates that occur close to thermodynamic equilibrium conditions in chemical solution methods represent an advantageous alternative to physical deposition methods for the preparation of oxide thin films in which complex cationic ordering is involved.Using polymers to control the growth of ceramic thin films can make it easier to produce materials for spintronic applications, which use electron spin instead of charge to carry information.When the semiconductor lanthanum cobalt manganese oxide (La2CoMnO6) adopts a crystal arrangement known as a double perovskite structure, it takes on boosted magnetic properties.Narcis Mestres from the Institut de Cincia de Materials de Barcelona in Spain and colleagues have developed a fabrication strategy that lets La2CoMnO6 epitaxial thin films grow in an optimal orientation for device applications.The team used a mixture of water-soluble polymers to bind to metal cations and slow down crystallization rates so that the most thermodynamically favored perovskite structure formed.The resulting surfaces were smooth down to a nanometer scale, and had significantly higher magnetism than samples grown with conventional vapor deposition techniques.Double perovskites have a wide range of properties and a corresponding broad range of potential applications, including magneto-optic and spintronic devices.However, their electric, magnetic, and elastic properties are strongly dependent on the ordered arrangement of cations in the double perovskite structure.In this work we show that the particular crystallization and growth process conditions (very slow rate, close to thermodynamic equilibrium conditions) of Polymer Assisted Deposition (PAD), promote very high B-site cationic ordering.Confirmation of the achievement of full Co/Mn cationic ordering is found in PAD grown epitaxial La2CoMnO6/SrTiO3double perovskite thin films displaying optimal magnetic properties.