A magneto-optical Kerr effect system with a spatial resolution of 2 μm was used to measure the local M-H loops for the free layer of a magnetic tunnel junction with a structure of Ta/Cu/Ta/NiFe/Cu/Mn75Ir 25/Co70Fe30/Al2O3/Co 70Fe30/Ta to investigate the exchange bias field H E and the coercivity HC for the free layer. The H E and HC measured along the direction of the free layer varied symmetrically with respect to the junction center. The measurements indicate that the enhanced HC correlated with HE, and HE could be reasonably explained by using an "orange-peel- type" coupling based on variations in the thickness of the pinned layer along the direction of the free layer. The variation in HE along the pinned-layer's direction could be ascribed to that of the free-layer's thickness, and the increase in HE at the junction edge along the pinned layer was due to a decrease in the thickness of the free layer near the edge. However, the nearly constant HC along the pinned layer indicates that the thickness of the free layer can be excluded from the mechanism for enhancing HC, which is a unique difference in the parameters involved in HE and HC, and in the mechanism for enhancing HC.
ASJC Scopus subject areas
- Physics and Astronomy(all)