1. Heating asymmetry induced by tunneling current flow in magnetic tunnel junctions
- Author
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Clarisse Ducruet, R. C. Sousa, B. Dieny, C. Portemont, Y. Dahmane, Laurent Vila, K. Mackay, J.-P. Nozieres, Erwan Gapihan, Ioan Lucian Prejbeanu, J. Herault, SPINtronique et TEchnologie des Composants (SPINTEC), Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Service de Physique des Matériaux et Microstructures (SP2M - UMR 9002), Institut Nanosciences et Cryogénie (INAC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), CROCUS Technology, ANR-07-NANO-052-02 Project, and European Project: 246942,EC:FP7:ERC,ERC-2009-AdG,HYMAGINE(2010)
- Subjects
010302 applied physics ,[PHYS]Physics [physics] ,Materials science ,Physics and Astronomy (miscellaneous) ,Condensed matter physics ,Fermi level ,02 engineering and technology ,Dissipation ,021001 nanoscience & nanotechnology ,01 natural sciences ,symbols.namesake ,Tunnel magnetoresistance ,Exchange bias ,Ballistic conduction ,0103 physical sciences ,symbols ,Current (fluid) ,0210 nano-technology ,Joule heating ,Quantum tunnelling - Abstract
International audience; In this work, exchange bias was used as a probe to characterise the temperature profile induced by the inelastic relaxation of electrons tunnelling across a MgO barrier. Thermally assisted magnetic random access memory (TA-MRAM) cells comprising a magnetic tunnel junction (MTJ) with a reference pinned layer and a FeMn exchange biased storage layer were used. The pinning direction of the ferromagnetic storage layer is reversed when heated above the blocking temperature of the antiferromagnetic layer (FeMn). The power density required to reach this blocking temperature in the FeMn layer depends on the current polarity, indicating that the heat source term associated with the current flowing through the barrier depends itself on the current direction in contrast to simple Joule heating. This effect is due to the mechanism of energy dissipation in tunnelling. The tunnelling itself is ballistic i.e., without dissipation. However, after tunnelling, the hot electrons very quickly relax to the Fermi energy thereby loosing their excess energy in the receiving electrode. Therefore, the heat is essentially generated on one side of the barrier so that the whole profile of temperature throughout the pillar depends on the current direction. Full 3D thermal simulations also confirmed the temperature profile asymmetry. The proper choice of heating current direction (i.e., voltage polarity applied to the MTJ) can yield a reduction of about 10% in the heating power density required to enable writing in thermally assisted MRAM cells.
- Published
- 2012
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