Abstract
The electrical characteristics of single-type magnetic tunnel junctions (MTJs), Co/Al 2O 3/Ni 80Fe 20, were studied by means of the I–V, G–V, Z complex impedance spectra data along with the Simmons’ and Brinkman's fitting procedure. A Coulomb blockade (CB)-like phenomenon was observed in some of the single MTJ samples in the form of periodic peaks in the G–V curves. This effect is attributed to the quantized charge transport through the ferromagnetic “nano-islands” formed within the Al 2O 3 layer. Artificial island-type MTJs were fabricated by inserting a very thin Co layer into the Al 2O 3 barrier layer, Co/Al 2O 3/Co/Al 2O 3/Ni 80Fe 20, followed by annealing. The observed CB behavior in these island-type MTJs not only strongly supports the explanation to the described effect in the single MTJs but also demonstrates the possibility to fabricate the MTJs with the intended CB for application.
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