Annealing of CoFeB/MgO based single and double barrier magnetic tunnel junctions: Tunnel magnetoresistance, bias dependence, and output voltage

Co40Fe40B20/MgO single and double barrier magnetic tunnel junctions (MTJs) were grown using target-facing-target sputtering for MgO barriers and conventional dc magnetron sputtering for Co40Fe40B20 ferromagnetic electrodes. Large tunnel magnetoresistance (TMR) ratios, 230% for single barrier MTJs and 120% for the double barrier MTJs, were obtained after postdeposition annealing in a field of 800 mT. The lower TMR ratio for double barrier MTJs can be attributed to the amorphous nature of the middle Co40Fe40B20 free layer, which could not be crystallized during postannealing. A highly asymmetric bias voltage dependence of the TMR can be observed for both single and double barrier MTJs in the as-deposited states and after field annealing at low temperature. The asymmetry decreases with increasing annealing temperature and the bias dependence becomes almost symmetric after annealing at 350 °C. Maximum output voltages of 0.65 and 0.85 V were obtained for both single and double barrier MTJs, respectively, after...

[1]  T. Miyazaki,et al.  Giant magnetic tunneling e ect in Fe/Al2O3/Fe junction , 1995 .

[2]  Kinder,et al.  Large magnetoresistance at room temperature in ferromagnetic thin film tunnel junctions. , 1995, Physical review letters.

[3]  Peter M. Levy,et al.  Quenching of magnetoresistance by hot electrons in magnetic tunnel junctions , 1997 .

[4]  Kazuhiro Saito,et al.  Influence of crystal structure and oxygen content on exchange-coupling properties of IrMn/CoFe spin-valve films , 1999 .

[5]  M. Sato,et al.  Effects of interface oxidization in ferromagnetic tunnel junctions , 1999, IEEE International Magnetics Conference.

[6]  K. Inomata,et al.  Magnetoresistance oscillations in-double ferromagnetic tunnel junctions with layered ferromagnetic nanoparticles , 2000 .

[7]  T. Schulthess,et al.  Spin-dependent tunneling conductance of Fe | MgO | Fe sandwiches , 2001 .

[8]  A. Umerski,et al.  Theory of tunneling magnetoresistance of an epitaxial Fe/MgO/Fe(001) junction , 2001 .

[9]  M. Gillies,et al.  Asymmetric bias voltage dependence of the magnetoresistance of Co/Al2O3/Co magnetic tunnel junctions: Variation with the barrier oxidation time , 2001 .

[10]  G. Gieres,et al.  Low tunnel magnetoresistance dependence versus bias voltage in double barrier magnetic tunnel junction , 2003 .

[11]  Magnon- and phonon-assisted tunneling in a high-magnetoresistance tunnel junction using Co75Fe25 ferromagnetic electrodes , 2003, cond-mat/0302210.

[12]  S. Lee,et al.  Interface and microstructure evolutions in synthetic ferrimagnet-based spin valves upon exposure to postdeposition annealing , 2003 .

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

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

[15]  Shoji Ikeda,et al.  Dependence of Giant Tunnel Magnetoresistance of Sputtered CoFeB/MgO/CoFeB Magnetic Tunnel Junctions on MgO Barrier Thickness and Annealing Temperature , 2005 .

[16]  S. Dijken,et al.  Influence of the annealing field strength on exchange bias and magnetoresistance of spin valves with IrMn , 2005 .

[17]  N. Tezuka,et al.  Bias voltage effect on tunnel magnetoresistance in fully epitaxial MgO double-barrier magnetic tunnel junctions , 2005 .

[18]  K. Tsunekawa,et al.  230% room temperature magnetoresistance in CoFeB/MgO/CoFeB magnetic tunnel junctions , 2005, INTERMAG Asia 2005. Digests of the IEEE International Magnetics Conference, 2005..

[19]  J. M. D. Coey,et al.  Influence of annealing on the bias voltage dependence of tunneling magnetoresistance in MgO double-barrier magnetic tunnel junctions with CoFeB electrodes , 2006 .

[20]  Shoji Ikeda,et al.  Effect of high annealing temperature on giant tunnel magnetoresistance ratio of CoFeB/MgO/CoFeB magn , 2006, cond-mat/0610526.

[21]  Ming-Jinn Tsai,et al.  Interfacial and annealing effects on magnetic properties of CoFeB thin films , 2006 .

[22]  W. C. Lim,et al.  Compositional change of MgO barrier and interface in CoFeB / MgO / CoFeB tunnel junction after annealing , 2006 .

[23]  J. Zhu,et al.  Annealing effects on structural and transport properties of rf-sputtered CoFeB∕MgO∕CoFeB magnetic tunnel junctions , 2006 .

[24]  Gang Xiao,et al.  Thermal stability of magnetic tunneling junctions with MgO barriers for high temperature spintronics , 2006 .

[25]  Xiufeng Han,et al.  High magnetoresistance in Co–Fe–B-based double barrier magnetic tunnel junction , 2006 .

[26]  S. Ikeda,et al.  Effect of electrode composition on the tunnel magnetoresistance of pseudo-spin-valve magnetic tunnel junction with a MgO tunnel barrier , 2007 .

[27]  W. C. Lim,et al.  Structural analysis of the CoFeB thin film in Ru∕CoFeB and MgO∕CoFeB layers , 2007 .

[28]  K. Tsunekawa,et al.  Crystallization of Amorphous CoFeB Ferromagnetic Layers in CoFeB/MgO/CoFeB Magnetic Tunnel Junctions , 2007 .

[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 .