Interplay between size and shape in the magnetic behaviour of epitaxial microtunnel junction arrays

Abstract

Arrays of epitaxial Fe/MgO/Fe planar tunnel junction elements have been fabricated with square or rectangular shape, micrometric sizes and nanometric interdistances in order to study the role of element shape geometry in the magnetic behaviour of these small structures. The elements are patterned from a continuous fully epitaxial trilayer by electron beam lithography. Magneto-optical measurements show that the patterning drastically modifies the magnetization reversal behaviour which can be tailored with the particular shape dimensions of the junction elements. In square elements, hysteresis loops with two stages and a remanence Mr ~ 0 are observed, revealing the antiparallel alignment due to top–bottom magnetostatic interaction. On the other hand, rectangular elements of a similar area present Mr ~ 1 and a two step reversal process when the field sign is changed, so that the magnetic state can be switched from parallel to antiparallel layer magnetization just by applying a small magnetic field.