Spintronics is a technique that uses the spin of electrons in electronic devices. The principle is based on physical properties such as magnetoresistance, (Nobel Prize 2007, Albert Fert), meaning that the electric conductivity of a system can depend on the magnetic field applied to the device. The spin-polarized scanning tunneling microscope (SP-STM) is a perfect example of this physics. It involves a magnetic tip and a magnetic surface ; therefore is an essential tool for local analysis of electronic and magnetic properties of surfaces. The aim of our study is to understand and simulate spin-polarized scanning tunneling microscopy images of a Cr(001) surface going beyond the classical Tersoff-Hamann approximation. We use an textitab initio method using PWSCF package, alongside a tight binding approach (TB) well fitted. First, we have performed a very detailed study of chromium electronic and magnetic properties, focusing deeply on surface states localized around the Fermi level. As a matter of fact, there is a controversy concerning the understanding of spectra obtained by STS. We have clearly identified surface states involved, and noticed that the peak in question is of a dz2 − pz symmetry. We have studied the decay of orbital wavefunctions above the Cr(001) surface to see that the PDOS that would be observed by STS would be a mix of pz and dz2 orbitals. Finally, in order to study the ballistic electronic transport, we have simulated an ideal system corresponding to a SP-STM set-up, namely Fe(001)-Cr(001) surfaces separated by vacuum. We have also simulated a real Fe tip-Cr(001) system as a tunneling contact. THe general behavior and the resulting TMR are in good agreement with experimental results.
