Nanoelectronics Understanding Quantum Transport in Magnetic Tunnel Junctions

Electron Tunneling is one of the most important subjects in condensed matter physics and provides an important and versatile spectroscopic tool for the experimentalists. Ferromagnetic metals are ideal contacts for spin injection and detection, but the intervening tunnel barrier required to accommodate the large difference in conductivity introduces defects, trapped charge and material interdiffusion, which severely compromise performance. In particular Magnetic Tunnel Junctions (MTJs) with MgO barriers are a subject that has aroused the interest of the scientific community in the last decade. The interest in such MTJs based devices arise from the room temperature Large Tunnel Magnetoresistence (TMR) theoretically predicted in the beginning of this century and the important number of technological applications such as forefront spin-transfer-torque magnetic random access memories, read heads, novel microwave devices and sensors for small magnetic fields.

The objectives of the present project are:

• Development of a methodology to calculate the elastic conductance in tunnel junctions starting from DFT calculations.

– Study of the electronic structure of Fe/MgO/Fe magnetic tunnel junctions from ab-initio (Density functional Theory) calculation.

– Study of the elastic conductance using as starting point the Hamiltonian obtained in the previous point.

• Understanding the different inelastic phenomena that compromise the large Tunnel Magnetic Resistance (TMR) in these systems.

– Study of the inelastic conductance taking as a starting point Density Functional Theory calculations and including inelastic effects using perturbation theory.

Even the main subject is to study the elastic and inelastic tunnel in Fe/MgO/Fe magnetic tunnel junctions, we think that the methodology developed in this project can be useful for the study of different tunnel junction based devices. The main objective of the present plan is to improve the overall understanding of the inelastic electron tunneling spectroscopy (IETS) in magnetic junctions.