Magnetotransport characteristics of strained La 0.7 Sr 0.3 MnO 3 epitaxial manganite films

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SORDER, AND PHASE TRANSITION IN CONDENSED SYSTEMS

Magnetotransport Characteristics of Strained La0.7Sr0.3MnO3 Epitaxial Manganite Films G. A. Ovsyannikova, b, *, A. M. Petrzhika, I. V. Borisenkoa, A. A. Klimova, Yu. A. Ignatova, V. V. Demidova, and S. A. Nikitova a

Institute of Radio-Engineering and Electronics, Russian Academy of Sciences, Mokhovaya 11, Moscow, 125009 Russia * e-mail: [email protected] b Chalmers University of Technology, Göteborg, SE-41296 Sweden Received April 4, 2008

Abstract—The electrical and magnetic characteristics of La0.7Sr0.3MnO3 (LSMO) epitaxial manganite films are investigated by different methods under conditions when the crystal structure is strongly strained as a result of mismatch between the lattice parameters of the LSMO crystal and the substrate. Substrates with lattice parameters larger and smaller than the nominal lattice parameter of the LSMO crystal are used in experiments. It is shown that the behavior of the temperature dependence of the electrical resistance for the films in the lowtemperature range does not depend on the strain of the film and agrees well with the results obtained from the calculations with allowance made for the interaction of electrons with magnetic excitations in the framework of the double-exchange model for systems with strongly correlated electronic states. Investigations of the magneto-optical Kerr effect have revealed that an insignificant (0.3%) orthorhombic distortion of the cubic lattice in the plane of the NdGaO3(110) substrate leads to uniaxial anisotropy of the magnetization of the film, with the easy-magnetization axis lying in the substrate plane. However, LSMO films on substrates (((LaAlO3)0.3 + (Sr2AlTaO6)0.7)(001)) ensuring minimum strain of the films exhibit a biaxial anisotropy typical of cubic crystals. The study of the ferromagnetic resonance lines at a frequency of 9.76 GHz confirms the results of magnetooptical investigations and indicates that the ferromagnetic phase in the LSMO films is weakly inhomogeneous. PACS numbers: 74.45.+c, 74.50.+r, 75.70.Cn DOI: 10.1134/S1063776109010075

1. INTRODUCTION

However, a number of problems associated with the influence of the strain on the electrical and magnetic properties of LSMO films have remained unclear and call for further investigation. There is no experimentally confirmed model of the temperature dependence of the electrical resistance for films at low temperatures [4], the problems regarding the influence of the film strain on the magnetic anisotropy [3] and the Curie temperature [5, 6] remain unsolved, etc.

Rare-earth manganite perovskites Re1 – xAxMnO3 (where Re is a rare-earth element of the La or Nd type and A is an alkaline-earth metal of the Sr or Ca type) exhibit a wide spectrum of unusual electrical and magnetic properties, including the colossal magnetoresistance effect (see reviews [1–4]). The parameters of epitaxial films of these materials very often differ substantially from the characteristics of single crystals. As was shown in a number of works [2, 3, 5–12],