Noise Measurement in Magnetic Tunnel Junctions

An investigation has been carried out on the low frequency noise in magnetic tunnel junctions in various magnetic states. The noise measurements show similar 1/f spectra in either the parallel or antiparallel magnetic state. The transition region of applied magnetic field, switching from parallel to antiparallel and vice versa, indicates a 1/f$^{2}$ spectrum along with an increase in the low frequency noise. This 1/f$^{2}$ spectrum and noise increase is found to be an artifact resulting from the magnetic after effect which occurs in the magnetic switching regions. Removing the effects of the magnetic after effect, only 1/f spectra are measured. The shot noise at higher frequency where the 1/f noise is negligible is also found in the tunnel junctions. Though it appears to be linear with the applied current, the shot noise observed can be largely enhanced.