Dynamic Lorentz microscopy of micromagnetic structure in magnetic tunnel junctions

Lorentz microscopy was used to study the micromagnetic structure and magnetization reversal in magnetic tunnel junctions (MTJs) fabricated with different processing conditions including a preoxidation process. The authors find that the free layer in a MTJ has considerably more disorder than that seen in an isolated magnetic layer. The disorder changes with anneals that set the exchange bias, suggesting that the disorder arises from the antiferromagnetic layer and is transferred to the free layer by magnetostatic Neel coupling. The disorder and time-dependent fluctuations in the magnetic structure provide a foundation for understanding several sources of 1/f noise in MTJs. (c) 2006 American Institute of Physics.