Gap state charge induced spin-dependent negative differential resistance in tunnel junctions
1 Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences Beijing 100190, China
2 Department of Physics and the Quantum Theory Project, University of Florida - Gainesville, FL 32611, USA
Received: 31 December 2015
Accepted: 16 April 2016
We propose and demonstrate through first-principles calculation a new spin-dependent negative differential resistance (NDR) mechanism in magnetic tunnel junctions (MTJ) with cubic cation disordered crystals (CCDC) AlOx or Mg1−xAlxO as barrier materials. The CCDC is a class of insulators whose band gap can be changed by cation doping. The gap becomes arched in an ultrathin layer due to the space charge formed from metal-induced gap states. With an appropriate combination of an arched gap and a bias voltage, NDR can be produced in either spin channel. This mechanism is applicable to 2D and 3D ultrathin junctions with a sufficiently small band gap that forms a large space charge. It provides a new way of controlling the spin-dependent transport in spintronic devices by an electric field. A generalized Simmons formula for tunneling current through junction with an arched gap is derived to show the general conditions under which ultrathin junctions may exhibit NDR.
PACS: 72.25.-b – Spin polarized transport / 73.50.Fq – High-field and nonlinear effects / 81.05.Zx – New materials: theory, design, and fabrication
© EPLA, 2016