High Magnetoresistance in Tunnel Junctions with Superlattice Barrier
C. H. Chen1*, R. Z. Qiu1, Y. H Cheng1, W. J. Hsueh1
1Department of Engineering Science and Ocean Engineering, National Taiwan University, Taipei, Taiwan
* presenting author:Chang Hung Chen, email:f96525066@ntu.edu.tw
In this study, we investigate the transmission spectra and the tunnel magnetoresistance (TMR) of a magnetic tunnel junction (MTJ) with a superlattice barrier composed of nonmagnetic metal and insulator. Under proper design, TMR ratio over 10⁴% can be reached. Compared to traditional MgO-based MTJ, superlattice-based MTJ can have better performance. Similarly to crystalline MgO, superlattice barrier also has crystalline properties which are the key to obtaining large TMR ratio. Moreover, there are more adjustable parameters, such as the lattice constant and the barrier height, in the artificial superlattice barrier than in a traditional crystalline-MgO barrier. Spin-dependent resonant tunneling of the superlattice-based MTJ is also studied. When the maximum of TMR ratio occurs at a certain thickness of the nonmagnetic metal layer, no resonant tunneling peaks appear in anti-parallel configuration. Therefore, the current in anti-parallel configuration will be small and the TMR ratio will be large. This ultrahigh TMR effect may be used to design spintronic devices.

Keywords: Tunnel magnetoresistance, Magnetic tunnel junctions, Superlattices