Observation of change in the oxidation state at ferromagnet/insulator interface upon thermal annealing
Department of Physics, University of Connecticut 2152 Hillside Road, Storrs, CT 06269, USA
2 Advanced Photon Source, Argonne National Laboratory 9700 S. Cass Avenue, Argonne, IL 60439, USA
3 IBM Almaden Research Center - 650 Harry Road San Jose, CA 95120, USA
Accepted: 28 May 2001
It is reported that the magnetoresistance (MR) of magnetic tunneling junction (MTJ) like improves upon thermal annealing. We investigate the mechanism of this improvement by comparing the X-ray absorption spectra (XAS) of half-MTJ structures (/) before and after annealing. Before annealing, XAS show the presence of few angstroms of - and -oxides, which disappeared after annealing at 250 °C for 1/2 hour. We attribute enhanced MR upon annealing to the disappearance of and oxides at the interface which reduce the spin-polarization of the conduction electrons and cause spin-flip scattering, both leading to inferior performance of MTJ.
PACS: 85.75.Ss – Magnetic field sensors using spin polarized transport / 82.65.+r – Surface and interface chemistry; heterogeneous catalysis at surfaces / 81.05.Je – Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
© EDP Sciences, 2001