Controlled fabrication of nano-scale double barrier magnetic tunnel junctions using focused ion beam milling method

The controlled fabrication method for nano-scale double barrier magnetic tunnel junctions (DBMTJs) with the layer structure of Ta(5)/Cu(10)/Ni79Fe21(5)/Ir22Mn78(12)/Co60Fe20B20(4)/Al(1)–oxide/Co60Fe20B20(6)/Al(1)–oxide/Co60Fe20B20(4)/Ir22Mn78(12)/Ni79Fe21(5)/Ta(5) (thickness unit: nm) was used. This method involved depositing thin multi-layer stacks by sputtering system, and depositing a Pt nano-pillar using a focused ion beam which acted both as a top contact and as an etching mask. The advantages of this process over the traditional process using e-beam and optical lithography in that it involve only few processing steps, e.g. it does not involve any lift-off steps. In order to evaluate the nanofabrication techniques, the DBMTJs with the dimensions of 200 nm×400 nm, 200 nm×200 nm nano-scale were prepared and their R–H, I–V characteristics were measured.