Realization of an effective ultrahigh magnetic field on a nanoscale

In tunnel junctions of which at least one side is a ferromagnet, very large magnetic polarization change (≈ 0.1μ_B) and splitting of the spin-up and spin-down Fermi energy (≈ 0.1 eV) can be created under steady state finite current conditions (bias voltage ≈ 1 volt). This is much higher than can be created by the highest magnetic field on earth. We illustrate this with a specific calculation of a recently observed very large Hall effect in the Al side of a Co-I-Al tunnel junction. Other recent experiments that support this idea are discussed.