Spatial control of magnetic anisotropy for current induced domain wall injection in perpendicularly magnetized CoFeB|MgO nanostructures

Magnetic anisotropy of perpendicularly magnetized CoFeB|MgO films is spatially tailored using depth controlled Ar ion etching with patterned etching masks. Nanowires with patterned etching have significantly reduced coercivity compared to those without the etching. We show that the sign of the anisotropy can be locally changed by partially etching the MgO layer, and as a consequence, 90° domain walls can be created at the boundary of etched/non-etched region. Direct current application to the nanowire can result in moving such 90° domain walls, which can prove as an efficient mean to inject domain walls into perpendicularly magnetized nanowires.

[1]  Effect of spin current on uniform ferromagnetism: domain nucleation. , 2005, Physical review letters.

[2]  H. Ohno,et al.  Current-induced domain wall motion in perpendicularly magnetized CoFeB nanowire , 2011 .

[3]  L. Buda-Prejbeanu,et al.  Fast current-induced domain-wall motion controlled by the Rashba effect. , 2011, Nature materials.

[4]  M. Gajek,et al.  Size dependence of spin-torque induced magnetic switching in CoFeB-based perpendicular magnetization tunnel junctions (invited) , 2012 .

[5]  D. Ravelosona,et al.  Tailoring magnetism by light-ion irradiation , 2004 .

[6]  Bernard Rodmacq,et al.  Current-driven spin torque induced by the Rashba effect in a ferromagnetic metal layer. , 2010, Nature materials.

[7]  A. Aziz,et al.  Artificial domain structures realized by local gallium focused Ion-beam modification of Pt∕Co∕Pt trilayer transport structure , 2005 .

[8]  S. Yuasa,et al.  Giant room-temperature magnetoresistance in single-crystal Fe/MgO/Fe magnetic tunnel junctions , 2004, Nature materials.

[9]  Hideo Ohno,et al.  Current-induced effective field in perpendicularly magnetized Ta/CoFeB/MgO wire , 2011 .

[10]  Controlled domain-wall injection in perpendicularly magnetized strips , 2010 .

[11]  Michael L. Schneider,et al.  Reversal mechanisms in perpendicularly magnetized nanostructures , 2008 .

[12]  Bruce D. Terris,et al.  Characterization of the magnetic modification of Co/Pt multilayer films by He+, Ar+, and Ga+ ion irradiation , 2002 .

[13]  H. Ohno,et al.  Current-Driven Magnetization Switching in CoFeB/MgO/CoFeB Magnetic Tunnel Junctions , 2005, INTERMAG 2006 - IEEE International Magnetics Conference.

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

[15]  H. Ohno,et al.  Dependence of magnetic anisotropy on MgO thickness and buffer layer in Co20Fe60B20-MgO structure , 2011 .

[16]  O. Hellwig,et al.  Influence of ion irradiation on switching field and switching field distribution in arrays of Co/Pd-based bit pattern media , 2011 .

[17]  J. Slonczewski.  Currents, torques, and polarization factors in magnetic tunnel junctions , 2004, cond-mat/0404210.

[18]  A. Panchula,et al.  Giant tunnelling magnetoresistance at room temperature with MgO (100) tunnel barriers , 2004, Nature materials.

[19]  G. Hu,et al.  Intrinsic distribution of magnetic anisotropy in thin films probed by patterned nanostructures. , 2006, Physical review letters.

[20]  S. Parkin,et al.  Magnetic Domain-Wall Racetrack Memory , 2008, Science.

[21]  T. Devolder,et al.  Planar patterned magnetic media obtained by ion irradiation , 1998, Science.

[22]  C. Rettner,et al.  Rotation and wall propagation in multidomain Co/Pd islands , 2005, IEEE Transactions on Magnetics.

[23]  Aurelien Manchon,et al.  Nonequilibrium intrinsic spin torque in a single nanomagnet , 2008 .

[24]  S. Seo,et al.  Tilting of the spin orientation induced by Rashba effect in ferromagnetic metal layer , 2010 .

[25]  Gen Tatara,et al.  Current-induced domain wall motion in Rashba spin-orbit system , 2008 .

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

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

[28]  H. Ohno,et al.  Domain wall dynamics driven by spin transfer torque and the spin–orbit field , 2012, Journal of physics. Condensed matter : an Institute of Physics journal.

[29]  H. Ohno,et al.  Tunnel magnetoresistance of 604% at 300K by suppression of Ta diffusion in CoFeB∕MgO∕CoFeB pseudo-spin-valves annealed at high temperature , 2008 .