journal article·2022-12Open access

Enhancing the interfacial perpendicular magnetic anisotropy and tunnel magnetoresistance by inserting an ultrathin LiF layer at an Fe/MgO interface

Takayuki Nozaki, Tomohiro Nozaki, Tatsuya Yamamoto, Makoto Konoto, Atsushi Sugihara, Kay Yakushiji, Hitoshi Kubota, Akio Fukushima, Shinji Yuasa

NPG Asia Materials· Volume 14· Issue 1

Abstract

Abstract Perpendicular magnetic anisotropy (PMA) is becoming increasingly important in spintronics research, especially for high-density magnetoresistive random access memories (MRAMs). The PMA induced at an Fe/MgO interface is widely used in magnetic tunnel junctions. Here, we propose inserting an ultrathin LiF layer at the interface in an epitaxial Fe/MgO junction. With a 0.3 nm-thick LiF layer, a large intrinsic interface PMA energy, Ki,0, of 2.8 mJ/m2 was achieved. We also found that the LiF/MgO bilayer tunneling barrier exhibited a large tunnel magnetoresistance (TMR) effect, suggesting that a coherent spin-dependent tunneling process was maintained in the ultrathin LiF layer. Atomic-scale interface engineering using fluoride can further improve the PMA and TMR properties of spintronic devices.
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Research context

OpenAlex topics: Magnetic properties of thin films · ZnO doping and properties · Magnetic Properties and Synthesis of Ferrites

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References (31)

Show source-provided references
1. Yuasa, S., Nagahama, T., Fukushima, A., Suzuki, Y. & Ando, K. Giant room-temperature magnetoresistance in single-crystal Fe/MgO/Fe magnetic tunnel junctions. Nat. Mater. 3, 868–871 (2004).10.1038/nmat1257 ↗
2. Parkin, S. S. et al. Giant tunnelling magnetoresistance at room temperature with MgO (100) tunnel barriers. Nat. Mater. 3, 862–867 (2004).10.1038/nmat1256 ↗
3. Ikeda, S. et al. A perpendicular-anisotropy CoFeB–MgO magnetic tunnel junction. Nat. Mater. 9, 721–724 (2010).10.1038/nmat2804 ↗
4. Yang, H. X. et al. First-principles investigation of the very large perpendicular magnetic anisotropy at Fe|MgO and Co|MgO interfaces. Phys. Rev. B 84, 054401 (2011).10.1103/PhysRevB.84.054401 ↗
5. Okabayashi, J. et al. Perpendicular magnetic anisotropy at the interface between ultrathin Fe film and MgO studied by angular-dependent X-ray magnetic circular dichroism. Appl. Phys. Lett. 105, 122408 (2014).10.1063/1.4896290 ↗
6. Ikeda, S. et al. Recent progress of perpendicular anisotropy magnetic tunnel junctions for nonvolatile VLSI. Spin 02, 1240003 (2012).10.1142/S2010324712400036 ↗
7. Amiri, P. K. et al. Electric-Field-Controlled Magnetoelectric RAM: Progress, Challenges, and Scaling. IEEE Trans. Magn. 51, 3401507 (2015).10.1109/TMAG.2015.2443124 ↗
8. Nozaki, T. et al. Recent progress in the voltage-controlled magnetic anisotropy effect and the challenges faced in developing voltage-torque MRAM. Micromachines 10, 327 (2019).10.3390/mi10050327 ↗
9. Worledge, D. C. et al. Spin torque switching of perpendicular Ta∣CoFeB∣MgO-based magnetic tunnel junctions. Appl. Phys. Lett. 98, 022501 (2011).10.1063/1.3536482 ↗
10. Pai, S.-F. et al. Enhancement of perpendicular magnetic anisotropy and transmission of spin-Hall-effect-induced spin currents by a Hf spacer layer in W/Hf/CoFeB/MgO layer structures. Appl. Phys. Lett. 104, 082407 (2014).10.1063/1.4866965 ↗
11. Sinha, J. et al. Enhanced interface perpendicular magnetic anisotropy in Ta|CoFeB|MgO using nitrogen-doped Ta underlayers. Appl. Phys. Lett. 102, 242405 (2013).10.1063/1.4811269 ↗
12. Sato, H. et al. Perpendicular-anisotropy CoFeB−MgO magnetic tunnel junctions with a MgO/CoFeB/Ta/CoFeB/MgO recording structure. Appl. Phys. Lett. 101, 022414 (2012).10.1063/1.4736727 ↗
13. Kubota, H. et al. Enhancement of perpendicular magnetic anisotropy in FeB free layers using a thin MgO cap layer. J. Appl. Phys. 111, 07C723 (2012).10.1063/1.3679393 ↗
14. Xiang, Q., Mandal, R., Sukegawa, H., Takahashi, Y. K. & Mitani, S. Large perpendicular magnetic anisotropy in epitaxial Fe/MgAl2O4(001) heterostructures. Appl. Phys. Exp. 11, 063008 (2018).10.7567/APEX.11.063008 ↗
15. Nozaki, T. et al. Highly efficient voltage control of spin and enhanced interfacial perpendicular magnetic anisotropy in iridium-doped Fe/MgO magnetic tunnel junctions. NPG Asia Mater. 9, e451–e451 (2017).10.1038/am.2017.204 ↗
16. Nozaki, T. et al. Enhancement in the interfacial perpendicular magnetic anisotropy and the voltage-controlled magnetic anisotropy by heavy metal doping at the Fe/MgO interface. APL Mater. 6, 026101 (2018).10.1063/1.5018162 ↗
17. Pankieiev, M. & Kita, K. Effects of oxide replacement with fluoride at the CoFeB interface on interface magnetic anisotropy and its voltage control. AIP Adv. 8, 055901 (2018).10.1063/1.5006420 ↗
18. Xue, Q. et al. Tunnel magnetoresistance in epitaxial (100)-oriented FeCo/LiF/FeCo magnetic tunnel junctions. Appl. Phys. Lett. 109, 192407 (2016).10.1063/1.4967473 ↗
19. Narayananellore, S. K., Doko, N., Matsuo, N., Saito, H. & Yuasa, S. Fabrication of magnetic tunnel junctions with a single-crystalline LiF tunnel barrier. Jpn. J. Appl. Phys. 57, 04FN04 (2018).10.7567/JJAP.57.04FN04 ↗
20. Liu, F. et al. Resonant TMR inversion in LiF/EuS based spin-filter tunnel junctions. AIP Adv. 6, 085004 (2016).10.1063/1.4960837 ↗
21. Vlaic, P., Burzo, E. & Carva, K. Are insulating LiF barriers relevant for spin-polarized tunnelling applications? Insights from first-principles calculations. J. Phys. D: Appl. Phys. 49, 305302 (2016).10.1088/0022-3727/49/30/305302 ↗
22. Mitani, S., Moriyama, T. & Takanashi, K. Structure and tunnel magnetoresistance in Fe/MgF[sub 2]/Co junctions with an oxide seed layer on an Fe bottom electrode. J. Appl. Phys. 91, 7200 (2002).10.1063/1.1452200 ↗
23. Harada, K., Makabe, K. S., Akinaga, H. & Suemasu, T. Room temperature magnetoresistance in Fe3Si/CaF2/Fe3Si MTJ epitaxially grown on Si(111). J. Phys.: Conf. Ser. 266, 012088 (2011).10.1088/1742-6596/266/1/012088 ↗
24. Furubayashi, T. & Nakatani, I. Giant magnetoresistance in granular Fe–MgF2 films. J. Appl. Phys. 79, 6258 (1996).10.1063/1.362025 ↗
25. Kobayashi, N., Ohnuma, S., Masumoto, T. & Fujimori, H. (Fe–Co)–(Mg-fluoride) insulating nanogranular system with enhanced tunnel-type giant magnetoresistance. J. Appl. Phys. 90, 4159–4162 (2001).10.1063/1.1376415 ↗
26. Ono, K et al. Electrical Conduction and Tunneling Magnetoresistance of Fe,Co/MgF2 Granullar Multilayers. Jpn. J. Appl. Phy. 41, 97–102 (2002).10.1143/JJAP.41.97 ↗
27. Shiota, Y. et al. Quantitative evaluation of voltage-induced magnetic anisotropy change by magnetoresistance measurement. Appl. Phys. Exp. 4, 043005 (2011).10.1143/APEX.4.043005 ↗
28. Bloemen, P. J. H., Johnson, M. T., den Broeder, F. J. A. & de Vries, J. J. Magnetic anisotropy in metallic multilayers. Rep. Prog. Phys. 59, 1409–1458 (1996).10.1088/0034-4885/59/11/002 ↗
29. Nozaki, T. et al. Large voltage-induced changes in the perpendicular magnetic anisotropy of an MgO-based tunnel junction with an ultrathin Fe Layer. Phys. Rev. Appl. 5, 044006 (2016).10.1103/PhysRevApplied.5.044006 ↗
30. Koo, J. W. et al. Large perpendicular magnetic anisotropy at Fe/MgO interface. Appl. Phys. Lett. 103, 192401 (2013).10.1063/1.4828658 ↗
31. Sukegawa, H. et al. Tunnel magnetoresistance with improved bias voltage dependence in lattice-matched Fe/spinel MgAl2O4/Fe(001) junctions. Appl. Phys. Lett. 96, 212505 (2010).10.1063/1.3441409 ↗