Temperature dependence of magnetic and magnetotransport properties in BiFeO 3 thin films by pulsed laser deposition
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Temperature dependence of magnetic and magnetotransport properties in BiFeO3 thin films by pulsed laser deposition P. Tiberto1, G. Barrera1,2, F. Celegato1, M. Coïsson1, P. Rizzi2, F. Vinai1, A.C. Garcia Castro3, L. Salamanca-Riba4, R.D. Vispute4, F.J. Espinoza Beltran3, J. Muñoz Sandaña3 1 INRIM, Electromagnetism Division strada delle Cacce 91, 10135 Torino (TO), Italy 2 Università degli Studi di Torino, Dipartimento di Chimica via P. Giuria 7, 10125 Torino (TO), Italy 3 Unidad Queretaro, Centro de Investigacion y Estudios Avanzados del IPN Queretaro, Mexico 4 Materials Science and Engineering Department, University of Maryland Baltimore, Maryland, USA ABSTRACT Multiferroic BFO/SRO/Si trilayers have been prepared by pulsed laser deposition in the form of thin films. As a function of the BFO layer thickness, magnetic and magneto-transport properties have been investigated at room temperature and down to 5 K. At low BFO layer thickness, a residual γ-Fe2O3 phase, which interacts interfacially with the SRO and BFO layers, is responsible for moderately hard magnetic properties of the film. On increasing BFO layer thickness, more homogeneous deposits are obtained with uniform magnetic and magnetoresistive properties. INTRODUCTION Multiferroic materials have been extensively studied in recent years because of their unique feature of combining multiple ferroic properties at the same time [1,2,3,4]. As an example BiFeO3 (BFO) is a perovskite structure that is characterised by both ferroelectric and ferromagnetic properties at room temperature [5,6,7]. The possibility to control the orientation of the magnetisation in BFO systems using an electric field instead of a magnetic one makes them particularly interesting both for fundamental studies and for applications, especially in nanosructures, spintronics, and random access memories [8,9,10]. In this work, BFO thin films have been grown epitaxially on SRO underlayers by means of a pulsed laser deposition technique. Magnetic and magneto-resistance measurements have been used to investigate the role played by the BFO layer thickness on the magnetic properties of the bilayers. Inhomogeneities in the deposition at low BFO thickness and interfacial effects have been demonstrated to be significant in the room temperature and low temperature magnetisation reversal processes. EXPERIMENT SrRuO3 (SRO) layers have been deposited on Si(100) substrates by means of a multitarget pulsed laser deposition (PLD) setup, exploiting a KrF laser with a wavelength of 248 nm, an impulse of 1 J/cm2 with a duration of 20 ns and a repetition rate of 10 Hz. During the
deposition, the base pressure of the vacuum chamber was of the order of 1⋅10-7 mbar and the O2 pressure was of the order of 1 mbar. The substrate was heated at 650 °C. Subsequently, on top of the SRO layer, a BiFeO3 (BFO) layer has been deposited with the same technique, starting from Bi2O3 and Fe2O3 targets. The thickness of the two layers for the studied samples is reported in Table I. The preparation conditions are the same for both S
