Effects of a thin Mg layer on the structural and magnetoresistance properties of CoFeB/MgO/CoFeB magnetic tunnel junctions

Y. Lu , C. Deranlot (1) , A. Vaures (1) , F. Petroff (1) , J. -M. George , Y. Zheng (2) , D. Demailles

1 Laboratoire Albert Fert (ex-UMPhy Unité mixte de physique CNRS/Thales)
2 INSP - Institut des Nanosciences de Paris

We have combined in situ reflection high energy electron diffraction, high-resolution transmission electron microscopy, and magnetotransport experiments to investigate the role of a thin inserted Mg layer on the crystalline texture of MgO barriers in magnetic tunnel junctions grown in a standard sputtering system. It was found that an ultrathin Mg layer of 2-6 angstrom can efficiently promote a MgO (001) texture prior to any annealing. For thicker Mg layers, the MgO (001) texture was found to degrade due to the hexagonal structure of Mg. For tunneling magnetoresistance (TMR), the efficient role of the MgO crystallization induced by the Mg layer appears after a 400 degrees C annealing. The optimum was found for a 4 angstrom inserted Mg layer with a TMR of 120% at room temperature (210% at 3 K) which could be considerably improved for fully (001) oriented magnetic tunnel junctions. (c) 2007 American Institute of Physics. (c) 2007 American Institute of Physics.

Domaines: Matière Condensée [cond-mat]

Y. Lu, C. Deranlot, A. Vaures, F. Petroff, J. -M. George, et al.. Effects of a thin Mg layer on the structural and magnetoresistance properties of CoFeB/MgO/CoFeB magnetic tunnel junctions. Applied Physics Letters, 2007, 91 (22), pp.222504. ⟨10.1063/1.2819530⟩. ⟨hal-01293153⟩