Fabrication of Magnetic Tunnel Junctions with a Synthetic Ferrimagnetic Free Layer for Magnetic Field Sensor Applications

Magnetic tunnel junctions (MTJs) with a CoFeB/Ru/Ni80Fe20 synthetic ferrimagnetic free layer and an MgO barrier layer were fabricated. The effect of the shape and thickness of the free layer on the magnetic field sensor characteristics was systematically investigated. We achieved a high sensitivity of 4.8%/Oe in the MTJ with a 70-nm-thick Ni80Fe20 layer and an aspect ratio of 1.0. Here, sensitivity is defined as TMR/(2Hk), where TMR is tunnel magnetoresistance ratio in the MTJ and Hk is a magnetic anisotropy field of the free layer. Furthermore, we successfully increased the detection field range up to 230 Oe while keeping high sensitivity and linearity.

[1]  D. Lacour,et al.  Wide range and tunable linear TMR sensor using two exchange pinned electrodes , 2009, 0906.4267.

[2]  P. P. Freitas,et al.  Field detection in MgO magnetic tunnel junctions with superparamagnetic free layer and magnetic flux concentrators , 2009 .

[3]  S. Eguchi,et al.  Transmission electron microscopy study on the crystallization and boron distribution of CoFeB/MgO/CoFeB magnetic tunnel junctions with various capping layers , 2009 .

[4]  Gang Xiao,et al.  Field sensing characteristics of magnetic tunnel junctions with (001) MgO tunnel barrier , 2008 .

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

[6]  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..

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

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

[9]  Yingjian Chen,et al.  PtMn-based spin-dependent tunneling materials with thin alumina barrier fabricated by two-step natural oxidation , 2002 .

[10]  William J. Gallagher,et al.  Exchange-biased magnetic tunnel junctions and application to nonvolatile magnetic random access memory (invited) , 1999 .

[11]  Saied N. Tehrani,et al.  High density submicron magnetoresistive random access memory (invited) , 1999 .

[12]  Anita Fink,et al.  Picotesla field sensor design using spin-dependent tunneling devices , 1998 .

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

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

[15]  M. Oogane,et al.  Development of Highly Sensitive Terrestrial Sensor using TMR Junctions , 2008 .