High Magnetoresistance Ratio and Low Resistance–Area Product in Magnetic Tunnel Junctions with Perpendicularly Magnetized Electrodes

We fabricated perpendicularly magnetized MgO-based magnetic tunnel junctions (p-MgO-MTJs) with a [Co/Pt]n/CoFeB/CoFe bottom electrode layer (free layer) and a CoFe/CoFeB/TbFeCo top electrode layer (reference layer). The insertion of thin CoFeB/CoFe layers at the barrier/electrode interfaces and post-annealing at a relatively low temperature of 225 °C simultaneously yielded high magnetoresistance (MR) ratios of up to 85% at room temperature and a low resistance–area (RA) product of 4.4 Ω µm2. Such a high MR ratio in low-RA p-MgO-MTJs is the key to developing ultrahigh-density spin-transfer-torque magnetoresistive random access memories (MRAMs).

[1]  Koji Ando,et al.  Ultralow resistance-area product of 0.4Ω(μm)2 and high magnetoresistance above 50% in CoFeB∕MgO∕CoFeB magnetic tunnel junctions , 2006 .

[2]  I. Mertig,et al.  Tunneling magnetoresistance with amorphous electrodes , 2008 .

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

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

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

[6]  T. Miyazaki,et al.  Tunneling magnetoresistance of magnetic tunnel junctions using perpendicular magnetization L10-CoPt electrodes , 2008 .

[7]  Koji Ando,et al.  Giant tunneling magnetoresistance effect in low-resistance CoFeB∕MgO(001)∕CoFeB magnetic tunnel junctions for read-head applications , 2005 .

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

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

[10]  T. Daibou,et al.  Tunnel Magnetoresistance Over 100% in MgO-Based Magnetic Tunnel Junction Films With Perpendicular Magnetic L1$_{0}$-FePt Electrodes , 2008, IEEE Transactions on Magnetics.

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

[12]  A. Fert,et al.  Spin-torque-induced switching and precession in fully epitaxial Fe/MgO/Fe magnetic tunnel junctions , 2009 .

[13]  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..

[14]  P. L. Trouilloud,et al.  Magnetoresistance measurement of unpatterned magnetic tunnel junction wafers by current-in-plane tunneling , 2003 .

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

[16]  Shigeki Nakagawa,et al.  Perpendicular magnetic tunnel junction with tunneling magnetoresistance ratio of 64% using MgO (100) barrier layer prepared at room temperature , 2008 .

[17]  H. Ohno,et al.  Perpendicular Magnetic Tunnel Junctions with CoFe/Pd Multilayer Electrodes and an MgO Barrier , 2009, IEEE Transactions on Magnetics.

[18]  S. Yuasa,et al.  Effect of Ta getter on the quality of MgO tunnel barrier in the polycrystalline CoFeB∕MgO∕CoFeB magnetic tunnel junction , 2007 .

[19]  S. Yuasa,et al.  Dependence of spin-transfer switching current on free layer thickness in Co–Fe–B∕MgO∕Co–Fe–B magnetic tunnel junctions , 2006 .

[20]  L. Ye,et al.  Effect of Annealing and Barrier Thickness on MgO-Based Co/Pt and Co/Pd Multilayered Perpendicular Magnetic Tunnel Junctions , 2008, IEEE transactions on magnetics.

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

[22]  Shinji Yamagata,et al.  Novel Stack Structure of Magnetic Tunnel Junction with MgO Tunnel Barrier Prepared by Oxidation Methods: Preferred Grain Growth Promotion Seed Layers and Bi-layered Pinned Layer , 2009 .