Influence of the substrate on the anomalous Nernst effect of magnetite thin films
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Influence of the substrate on the anomalous Nernst effect of magnetite thin films. R. Ramos1, A. Anadón1,2, I. Lucas1,3, L. Farrell4, M.H. Aguirre1,2, R.G.S. Sofin5, I.V. Shvets4, P.A. Algarabel2,6, L. Morellón1,2, M.R. Ibarra1,2 1
Instituto de Nanociencia de Aragón, Universidad de Zaragoza, E-50018 Zaragoza, Spain. Departamento de Física de la Materia Condensada, Universidad de Zaragoza, E-50009 Zaragoza, Spain. 3 Fundación ARAID, 50018 Zaragoza, Spain. 4 Centre for Research on Adaptive Nanostructures and Nanodevices, School of Physics, Trinity College Dublin, Dublin 2, Ireland. 5 Department of Physics, College of Science, Sultan Qaboos University, Muscat, Oman. 6 Instituto de Ciencia de Materiales de Aragón, Universidad de Zaragoza and Consejo Superior de Investigaciones Científicas, 50009 Zaragoza, Spain. 2
ABSTRACT We present a comparative study of the anomalous Nernst effect (ANE), measured at room temperature for magnetite thin films deposited on different substrates in order to study the effects induced by the substrate, compressive or tensile strain and structural defects as anti-phase boundaries (APB), on the observed ANE. From our preliminary results we have observed an increase of the measured ANE in the case of compressive strain compared with the tensile one. Moreover our results also suggest that the density of APBs also play an important role in the ANE values. INTRODUCTION Thermoelectric effects are a consequence of the interaction between charge and heat currents with applications as electric cooling systems or thermal power generators. Despite decades of research into thermoelectric materials, the efficiency of such devices, which is described by their figure of merit (z =α2/ρκ), has remained low, due to the interdependence between the Seebeck (α) effect, the resistivity (ρ) and the thermal conductivity (κ). One common approach to increase the figure of merit is the phonon-glass electron-crystal, which consists on the minimization of the thermal conductivity of the material at the same time that the electrical conductivity is enhanced. However, there is a fundamental limitation in the electronic part of the thermal conductivity. One promising approach to overcome this problem and increase the versatility of thermoelectric devices involves exploiting the spin of the electron, in addition to its charge and transport properties. The discovery of the spin Seebeck effect (SSE) [1] and more particularly, its observation in magnetic insulators [2, 3] offers a new approach for thermoelectric energy conversion, since it involves properties of two different materials that can be optimized independently and the absence of mobile carriers in the thermally active part of the device removes the associated joule heating.
Therefore the study of magnetic oxides is of interest for the understanding of spin dependent thermoelectric properties and the heat-spin interaction, one such property is the anomalous Nernst effect (ANE), which consists on the generation of an electric field in the direction defined by the
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