Effect of MgO Underlying Layer on the Growth of GaOx Tunnel Barrier in Epitaxial Fe/GaOx/(MgO)/Fe Magnetic Tunnel Junction Structure

We investigated the effect of a thin MgO underlying layer (~3 monoatomic layers) on the growth of GaOx tunnel barrier in Fe/GaOx/(MgO)/Fe(001) magnetic tunnel junctions. To obtain a single-crystalline barrier, an in situ annealing was conducted with the temperature being raised up to 500 °C under an O2 atmosphere. This annealing was performed after the deposition of the GaOx on the Fe(001) bottom electrode with or without the MgO(001) underlying layer. Reflection high-energy electron diffraction patterns after the annealing indicated the formation of a single-crystalline layer regardless of with or without the MgO layer. Ex situ structural studies such as transmission electron microscopy revealed that the GaOx grown on the MgO underlying layer has a cubic MgAl2O4-type spinel structure with a (001) orientation. When without MgO layer, however, a Ga-Fe-O ternary compound having the same crystal structure and orientation as the crystalline GaOx was observed. The results indicate that the MgO underlying layer effectively prevents the Fe bottom electrode from oxidation during the annealing process. Tunneling magneto-resistance effect was observed only for the sample with the MgO underlying layer, suggesting that Ga-Fe-O layer is not an effective tunnel-barrier.

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

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

[3]  M. Miyao,et al.  Atomically Controlled Epitaxial Growth of Single-Crystalline Germanium Films on a Metallic Silicide , 2012, 1210.1027.

[4]  MgGa2O4 spinel barrier for magnetic tunnel junctions: Coherent tunneling and low barrier height , 2016, 1611.03606.

[5]  A. Dinia,et al.  Tunnel magnetoresistance in magnetic tunnel junctions with a ZnS barrier , 2001 .

[6]  均 金井,et al.  第一原理計算による超低RA(<0.5Ωμm2)トンネル接合の検討 , 2010 .

[7]  W. Wegscheider,et al.  Spin polarized tunneling through single-crystal GaAs(001) barriers , 2002 .

[8]  Masaaki Tanaka,et al.  Spin-dependent transport properties of a GaMnAs-based vertical spin metal-oxide-semiconductor field-effect transistor structure , 2015, 1510.07497.

[9]  Ikhtiar,et al.  Large magnetoresistance in Heusler-alloy-based epitaxial magnetic junctions with semiconducting Cu(In0.8Ga0.2)Se2 spacer , 2016 .

[10]  Susana Cardoso,et al.  Magnetic tunnel junction sensors with pTesla sensitivity , 2014 .

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

[12]  M. Hehn,et al.  Tantalum oxide as an alternative low height tunnel barrier in magnetic junctions , 2001 .

[13]  P. Lai,et al.  Review of Noise Sources in Magnetic Tunnel Junction Sensors , 2011, IEEE Transactions on Magnetics.

[14]  G. Kiriakidis,et al.  Indium oxide as a possible tunnel barrier in spintronic devices , 2005 .

[15]  J. Coey,et al.  Room-temperature magnetoresistance in CoFeB/STO/CoFeB magnetic tunnel junctions , 2009 .

[16]  M. Oogane,et al.  Fabrication of Magnetic Tunnel Junctions with Amorphous CoFeSiB Ferromagnetic Electrode for Magnetic Field Sensor Devices , 2013 .

[17]  S. Yuasa,et al.  Investigation on the formation process of single-crystalline GaOx barrier in Fe/GaOx/MgO/Fe magnetic tunnel junctions , 2017 .

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

[19]  Kazuo Kobayashi,et al.  TMR film and head technologies , 2006 .

[20]  T. Sagara,et al.  Magnetoresistive Sensors , 1993, IEEE Translation Journal on Magnetics in Japan.

[21]  Xiaoguang Zhang,et al.  Layer KKR approach to Bloch-wave transmission and reflection: Application to spin-dependent tunneling , 1999 .

[22]  Koichiro Inomata,et al.  Tunnel magnetoresistance with improved bias voltage dependence in lattice-matched Fe/spinel MgAl2O4/Fe(001) junctions , 2010 .

[23]  A. Panchula,et al.  Magnetic tunnel junctions with ZnSe barriers , 2003 .

[24]  C. H. de Groot,et al.  Gallium oxide as an insulating barrier for spin-dependent tunneling junctions , 2000 .

[25]  Shinji Yuasa,et al.  High Magnetoresistance in Fully Epitaxial Magnetic Tunnel Junctions with a SemiconductingGaOxTunnel Barrier , 2016 .

[26]  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..

[27]  H. Sato,et al.  Electrical detection of spin accumulation and relaxation in p -type germanium , 2017 .

[28]  Anita Fink,et al.  Picotesla Field Sensor Design Using Spin Dependent Tunneling Devices , 1998, 7th Joint MMM-Intermag Conference. Abstracts (Cat. No.98CH36275).

[29]  Origin of Very Low Effective Barrier Height in Magnetic Tunnel Junctions with a Semiconductor GaOx Tunnel Barrier , 2011 .

[30]  M. Eddrief,et al.  Structural and transport properties of epitaxial Fe/ZnSe/FeCo magnetic tunnel junctions , 2001 .

[31]  J. Herfort,et al.  Epitaxial Fe3Si/Ge/Fe3Si thin film multilayers grown on GaAs(001) , 2014 .

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