Influence of growth and annealing conditions on low-frequency magnetic 1/f noise in MgO magnetic tunnel junctions

Magnetic 1/f noise is compared in magnetic tunnel junctions with electron-beam evaporated and sputtered MgO tunnel barriers in the annealing temperature range 350-425 degrees C. The variation of the magnetic noise parameter (alpha(mag)) of the reference layer with annealing temperature mainly reflects the variation of the pinning effect of the exchange-bias layer. A reduction in alpha(mag) with bias is associated with the bias dependence of the tunneling magnetoresistance. The related magnetic losses are parameterized by a phase lag e, which is nearly independent of bias especially below 100 mV. The similar changes in magnetic noise with annealing temperature and barrier thickness for two types of MgO magnetic tunnel junctions indicate that the barrier layer quality does not affect the magnetic losses in the reference layer. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4764314]