Determining the tunnel spin-polarization density of states near the Fermi level using IR magnetoreflectance spectroscopy

We present the experimental results on magnetorefractive effect (MRE) in ferromagnetic metal-insulator multilayer films of different composition with tunnelling magnetoresistance (TMR). The shape and magnitude of the MRE dependences are found to be very sensitive to the effective polarization of the electron density of state near the Fermi level. The spin-polarization density of states around the Fermi level for ferromagnetic film is directly extracted from the magnetoreflection spectra in the middle infrared region. The influence of the ferromagnetic layer thickness on the spin-polarization of the tunnelling electrons and as results on the TMR and MRE effects has been determined.