Reduction of switching current density in perpendicular magnetic tunnel junctions by tuning the anisotropy of the CoFeB free layer

The spin torque switching behavior of perpendicular magnetic tunnel junctions consisting of a CoFeB free layer and a CoFeB/Ru/(Co/Pd)n exchanged coupled fixed layer is investigated. At first, the Ru and CoFeB layer thickness is tuned in the CoFeB/Ru/(Co/Pd)n structure to form a ferromagnetically exchange coupled structure with a strong PMA at an annealing treatment of 325 °C for 1 h. Then it is shown that that the CoFeB free layer thickness plays an important role in the switching current density. The switching current density decreases with the increase of the CoFeB free layer thickness. A minimum switching current density of 1.87 MA/cm2 is achieved for a device with 60 nm diameter. The mechanism involved in the switching current reduction with the decrease of CoFeB free layer thickness is also studied.

[1]  William J. Gallagher,et al.  Fabrication and characterization of MgO-based magnetic tunnel junctions for spin momentum transfer switching , 2007 .

[2]  J. Nowak,et al.  Spin torque switching of perpendicular Ta∣CoFeB∣MgO-based magnetic tunnel junctions , 2011 .

[3]  H. Ohno,et al.  A perpendicular-anisotropy CoFeB-MgO magnetic tunnel junction. , 2010, Nature materials.

[4]  Bernard Rodmacq,et al.  Pt/Co/oxide and oxide/Co/Pt electrodes for perpendicular magnetic tunnel junctions , 2009 .

[5]  H. Ohno,et al.  Junction size effect on switching current and thermal stability in CoFeB/MgO perpendicular magnetic tunnel junctions , 2011 .

[6]  J. Slonczewski.  Current-driven excitation of magnetic multilayers , 1996 .

[7]  J. Katine,et al.  Current-induced magnetization reversal in nanopillars with perpendicular anisotropy , 2006 .

[8]  Mark H. Kryder,et al.  Spin valves exchange biased by Co/Ru/Co synthetic antiferromagnets , 1998 .

[9]  H. Ohno,et al.  Magnetic Tunnel Junctions for Spintronic Memories and Beyond , 2007, IEEE Transactions on Electron Devices.

[10]  A. Natarajarathinam,et al.  Magnetic tunnel junctions with Co-based perpendicular magnetic anisotropy multilayers , 2010 .

[11]  Ilya Krivorotov,et al.  Switching current reduction using perpendicular anisotropy in CoFeB-MgO magnetic tunnel junctions , 2011 .

[12]  M. Nakayama,et al.  Spin transfer switching in TbCoFe∕CoFeB∕MgO∕CoFeB∕TbCoFe magnetic tunnel junctions with perpendicular magnetic anisotropy , 2008 .

[13]  S. Ikeda,et al.  MgO barrier-perpendicular magnetic tunnel junctions with CoFe/Pd multilayers and ferromagnetic insertion layers , 2009, 0910.4204.

[14]  Asano,et al.  Magnetoelastic contribution to the interface anisotropy of Pd/Co metallic multilayers. , 1996, Physical review. B, Condensed matter.

[15]  J. Katine,et al.  Ultrafast switching in magnetic tunnel junction based orthogonal spin transfer devices , 2010 .

[16]  High temperature annealing stability of magnetic properties in MgO-based perpendicular magnetic tunnel junction stacks with CoFeB polarizing layer , 2011 .

[17]  Berger.  Emission of spin waves by a magnetic multilayer traversed by a current. , 1996, Physical review. B, Condensed matter.

[18]  D. Dimitrov,et al.  Switching-current reduction in perpendicular-anisotropy spin torque magnetic tunnel junctions , 2010 .

[19]  Ilya Krivorotov,et al.  Deep subnanosecond spin torque switching in magnetic tunnel junctions with combined in-plane and perpendicular polarizers , 2011 .

[20]  Ilya Krivorotov,et al.  Low writing energy and sub nanosecond spin torque transfer switching of in-plane magnetic tunnel junction for spin torque transfer random access memory , 2011 .

[21]  J. Zhu,et al.  Spin Torque and Field-Driven Perpendicular MRAM Designs Scalable to Multi-Gb/Chip Capacity , 2006, IEEE Transactions on Magnetics.

[22]  B. Diény,et al.  Magnetoresistance in Co∕Pt based magnetic tunnel junctions with out-of-plane magnetization , 2008 .

[23]  Z. Diao,et al.  Spin transfer switching current reduction in magnetic tunnel junction based dual spin filter structures , 2005 .

[24]  Kay Yakushiji,et al.  Spin-polarized current-induced magnetization reversal in perpendicularly magnetized L10-FePt layers , 2006 .

[25]  H. Meng,et al.  Reduction of switching current by spin transfer torque effect in perpendicular anisotropy magnetoresistive devices (invited) , 2011 .

[26]  Z. Diao,et al.  Spin-transfer torque switching in magnetic tunnel junctions and spin-transfer torque random access memory , 2007 .

[27]  H. Meng,et al.  Annealing effects on CoFeB-MgO magnetic tunnel junctions with perpendicular anisotropy , 2011 .

[28]  J. Zhu,et al.  Co∕Pt multilayer based magnetic tunnel junctions using perpendicular magnetic anisotropy , 2008 .