Structural and Electrical Properties of Colossal Magnetoresistive LSMO Thin Films Prepared by KrF Laser Ablation Method
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Structural and Electrical Properties of Colossal Magnetoresistive LSMO Thin Films Prepared by KrF Laser Ablation Method Fumiaki Mitsugi1, Tomoaki Ikegami1, Kenji Ebihara1, Jagdish Narayan2 and Alexander M. Grishin3 1 Department of the Electrical and Computer Engineering, Kumamoto University, Kurokami, Kumamoto 860-8555, Japan 2 Department of the Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695-7916, USA 3 Department of Condensed Matter Physics, Royal Institute of Technology, S-10044 Stockholm, Sweden
ABSTRACT We prepared colossal magnetoresistive La0.8Sr0.2MnO3 thin films on the MgO, SrTiO3 and LaAlO3 single crystal substrates using KrF excimer pulsed laser ablation technique. The structural and electrical properties of the La0.8Sr0.2MnO3 thin films which were strained by the lattice mismatch are reported. The in-plane lattice mismatch between the La0.8Sr0.2MnO3 and MgO, SrTiO3 and LaAlO3 substrates are -7.8 %, -0.5 % and +2.3 %, respectively. The X-ray diffraction spectra of the films exhibited c-axis orientation. In the case of the La0.8Sr0.2MnO3 / LaAlO3 thin films with thickness over 100 nm, the divided (00l) peaks were observed. The surface morphology and transport property of the strongly stressed La0.8Sr0.2MnO3 / LaAlO3 were different from those of La0.8Sr0.2MnO3 / MgO and La0.8Sr0.2MnO3 / SrTiO3 thin films.
INTRODUCTION The perovskite manganites of the Re1-xAexMnO3 (Re : rare earth elements, Ae : alkaline earth elements) thin films have attracted much attention due to the negative colossal magnetoresistance (CMR) effect. The CMR thin films have potential for various device applications such as magnetic field sensor, hard disk read head and infrared bolometer. The large magnetoresistance (MR) ratio which is defined as (ρ0-ρH)/ρ0, where ρ0 and ρH are the resistivities measured at zero and H field is needed in low magnetic field and at room temperature. The transport properties of the CMR thin films are sensitive to the Mn3+ / Mn4+ (Re3+ / Ae2+) ratio and the radii of the Re3+ ion and Ae2+ ion [1-4]. There have been attempts to investigate the influence of these parameters on the crystalline structure, morphology and electrical property of the CMR thin films. Recently, there have been several reports on the La1-xSrxMnO3 (LSMO) thin films [5-8]. The LSMO system with 0.2 < x < 0.5 has higher resistivity peak temperature (Tp), close to Curie temperature, than that of a La1-xCaxMnO3 (LCMO) system [9-11] and is expected to apply the new device working at room temperature. The radius of Sr2+ ion and Ca2+ ion are 1.27 Å and 1.06 Å, respectively. The radius of perovskite A site of the LSMO is larger than that of LCMO, that is, the tolerance factor of the LSMO is very close to 1.00 and MnO6 octahedron is stable. The influence of strain caused by lattice mismatch between the thin film and substrate has been investigated. The understanding of the detailed influence of strain on the properties is desirable for the controlled preparation of the CMR thin films. When the stra
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