Oscillatory tunneling magnetoresistance in magnetic tunnel junctions with inserted nonmagnetic layer

From QCLab
Prof. Byong Chan Lee (Inha University)
  • Speaker: Prof. Byung Chan Lee (Inha University)
  • Date: Wednesday, February 1, 2017, at 17:00
  • Place: Jungho Seminar Room

When a crystalline nonmagnetic (NM) layer was inserted between the tunnel barrier and a magnetic layer in magnetic tunnel junctions (MTJs), it was observed that the tunneling magnetoresistance (TMR) decayed and oscillated as a function of the thickness of the nonmagnetic layer. In this talk, the TMR dependence on the NM layer is investigated theoretically. The conductance was calculated with the Landauer-Buttiker formalism, and the conductance difference between the parallel and anti-parallel magnetizations was given in an analytical form with the spin-dependent reflection amplitudes. In order to check the validity of our model, numerical calculations were carried out. An effective mass theory was adopted for the electronic structure of each materials, and several cases were considered. It was shown that our simple model agreed well with the results of the numerical calculations. Our model can be applied also to more realistic cases with the full-band structures. The oscillation period was determined from the external vectors of the Fermi surface of the NM material, and the selection rules for the oscillation period were obtained. Comparisons with the experimental data and the previous theoretical results will be presented.