Exchange biased CoFeB-MgO tunnel junctions at the onset of perpendicular anisotropy with in-plane/out-of-plane sensing capabilities

We investigate the transport properties of exchange biased CoFeB-MgO tunnel junctions at the onset of perpendicular anisotropy of the CoFeB free layer. Angular dependent measurements of the tunnel conductance (varying the applied magnetic field from the in-plane to the out-of-plane direction) show linear and hysteresis-free switching under low applied magnetic fields, demonstrating a new concept for a reversible in-plane/out-of-plane magnetoresistive sensor. State-of-the-art sensitivities were achieved, and a value of 0.4% TMR/Oe is observed in the direction perpendicular to the tunnel junction plane. An analysis of the anisotropy energies at play is performed based on a Stoner--Wohlfarth like model.

[1]  G Autès,et al.  Strong enhancement of the tunneling magnetoresistance by electron filtering in an Fe/MgO/Fe/GaAs(001) junction. , 2010, Physical review letters.

[2]  Camelia Albon,et al.  Tunneling magnetoresistance sensors for high resolutive particle detection , 2009 .

[3]  Paulo P. Freitas,et al.  Evidence of spin-polarized direct elastic tunneling and onset of superparamagnetism in MgO magnetic tunnel junctions , 2010 .

[4]  Siya Lozanova,et al.  Angular position device with 2D low-noise Hall microsensor , 2010 .

[5]  S. Cardoso,et al.  Resonant tunneling through electronic trapping states in thin MgO magnetic junctions. , 2011, Physical review letters.

[6]  S. Yuasa,et al.  Giant tunnel magnetoresistance in magnetic tunnel junctions with a crystalline MgO(0 0 1) barrier , 2007 .

[7]  J. Osborn.  Demagnetizing Factors of the General Ellipsoid , 1945 .

[8]  G. Reiss,et al.  Structural study of amorphous CoFeB thin films exhibiting in-plane uniaxial magnetic anisotropy , 2009 .

[9]  O. Heinonen,et al.  Perpendicular spin torque in magnetic tunnel junctions. , 2010, Physical review letters.

[10]  Gang Xiao,et al.  Effects of superparamagnetism in MgO based magnetic tunnel junctions , 2009 .

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

[12]  Z. Wen,et al.  Perpendicular magnetization of Co2FeAl full-Heusler alloy films induced by MgO interface , 2011 .

[13]  Siya Lozanova,et al.  A novel 3-D Hall magnetometer using subsequent measurement method , 2009 .

[14]  Tunneling processes in thin MgO magnetic junctions , 2010 .

[15]  Xg Zhang,et al.  Magnetic tunnel junction sensor with Co/Pt perpendicular anisotropy ferromagnetic layer , 2009 .

[16]  Gang Xiao,et al.  In situ detection of single micron-sized magnetic beads using magnetic tunnel junction sensors , 2005 .

[17]  Single-shot time-domain studies of spin-torque-driven switching in magnetic tunnel junctions. , 2009, Physical review letters.

[18]  Paulo P. Freitas,et al.  OPTIMIZATION AND INTEGRATION OF MAGNETORESISTIVE SENSORS , 2011 .

[19]  B. Diény,et al.  First-principles investigation of the very large perpendicular magnetic anisotropy at Fe|MgO and Co|MgO interfaces , 2010, 1011.5667.

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

[21]  William J. Gallagher,et al.  Shape-anisotropy-controlled magnetoresistive response in magnetic tunnel junctions , 1997 .

[22]  P. Freitas,et al.  The effect of pinhole formation/growth on the tunnel magnetoresistance of MgO-based magnetic tunnel junctions , 2009 .

[23]  J. M. D. Coey,et al.  Magnetoresistance sensor with an out-of-plane magnetized sensing layer , 2005 .

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

[25]  Paulo P. Freitas,et al.  Field detection in single and double barrier MgO magnetic tunnel junction sensors , 2008 .

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

[27]  D. Mauri,et al.  Temporal coherence of MgO based magnetic tunnel junction spin torque oscillators. , 2009, Physical review letters.

[28]  T. Ito,et al.  Electric field effects on magnetocrystalline anisotropy in ferromagnetic Fe monolayers , 2010 .

[29]  J. Coey,et al.  Magnetism and Magnetic Materials , 2001 .

[30]  Magnetic tunneling junction based magnetic field sensors: Role of shape anisotropy versus free layer thickness , 2011 .

[31]  N. P. Barradas,et al.  Effect of free layer thickness and shape anisotropy on the transfer curves of MgO magnetic tunnel junctions , 2008 .

[32]  Gang Xiao,et al.  Quantitative detection of DNA labeled with magnetic nanoparticles using arrays of MgO-based magnetic tunnel junction sensors , 2008 .

[33]  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 .

[34]  Chunghee Nam,et al.  Magnetic field sensing scheme using CoFeB∕MgO∕CoFeB tunneling junction with superparamagnetic CoFeB layer , 2006 .

[35]  J. Paul,et al.  Wide range and tunable linear TMR sensor using two exchange pinned electrodes , 2009 .

[36]  J. M. Slaughter,et al.  Materials for Magnetoresistive Random Access Memory , 2009 .