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 μm investigated. Additionally, these MTJs show large TMR ratio up to 40% after annealing at 250 °C for 60 min. These results demonstrate that a SyF free layer can be applied to future spintronics nanodevices.

[1]  Parkin,et al.  Oscillations in exchange coupling and magnetoresistance in metallic superlattice structures: Co/Ru, Co/Cr, and Fe/Cr. , 1990, Physical review letters.

[2]  William J. Gallagher,et al.  Two-dimensional magnetic switching of micron-size films in magnetic tunnel junctions , 2000 .

[3]  Saied N. Tehrani,et al.  Switching characteristics and magnetization vortices of thin-film cobalt in nanometer-scale patterned arrays , 2000 .

[4]  S. Parkin,et al.  Thickness-dependent magnetic properties of Ni81Fe19, Co90Fe10 and Ni65Fe15Co20 thin films , 2002 .

[5]  Bloemen,et al.  Oscillatory interlayer exchange coupling in Co/Ru multilayers and bilayers. , 1994, Physical review. B, Condensed matter.

[6]  E. Wohlfarth,et al.  A mechanism of magnetic hysteresis in heterogeneous alloys , 1948, Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences.

[7]  Koichiro Inomata,et al.  Magnetic switching field and giant magnetoresistance effect of multilayers with synthetic antiferromagnet free layers , 2002 .

[8]  P. Freitas,et al.  Synthetic ferrimagnet free layer tunnel junction for magnetic random access memories , 2002 .

[9]  Single domain observation for synthetic antiferromagnetically coupled bits with low aspect ratios , 2003 .

[10]  Naoki Kobayashi,et al.  GaN-free transparent ultraviolet light-emitting diodes , 2003 .

[11]  A. Dinia,et al.  Temperature dependence of the magnetoresistance in Co/Ru sandwich and superlattice structures , 1995 .