Magnetic switching properties of magnetic tunnel junctions using a synthetic ferrimagnet free layer

Magnetic tunnel junctions (MTJs) using a synthetic ferrimagnet (SyF) free layer consisting of Co90Fe10/Ru/Co90Fe10 were deposited on a thermally oxidized Si substrate using an ultrahigh-vacuum sputtering system, and were patterned into micron to submicron sizes using electron-beam lithography and Ar ion milling. Magnetic switching properties and tunneling magnetoresistance (TMR) were investigated. A SyF free layer can maintain high remanence even for the aspect ratio of 1, and exhibits a size-independent switching field in all element widths from 0.25 to 16 mum investigated. Additionally, these MTJs show large TMR ratio up to 40% after annealing at 250 degreesC for 60 min. These results demonstrate that a SyF free layer can be applied to future spintronics nanodevices. (C) 2004 American Institute of Physics.