Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Article
  • Published:

Spontaneous exchange bias formation driven by a structural phase transition in the antiferromagnetic material

Nature Materials volume 17, pages 28–35 (2018)Cite this article

Subjects

Abstract

Most of the magnetic devices in advanced electronics rely on the exchange bias effect, a magnetic interaction that couples a ferromagnetic and an antiferromagnetic material, resulting in a unidirectional displacement of the ferromagnetic hysteresis loop by an amount called the ‘exchange bias field’. Setting and optimizing exchange bias involves cooling through the Néel temperature of the antiferromagnetic material in the presence of a magnetic field. Here we demonstrate an alternative process for the generation of exchange bias. In IrMn/FeCo bilayers, a structural phase transition in the IrMn layer develops at room temperature, exchange biasing the FeCo layer as it propagates. Once the process is completed, the IrMn layer contains very large single-crystal grains, with a large density of structural defects within each grain, which are promoted by the FeCo layer. The magnetic characterization indicates that these structural defects in the antiferromagnetic layer are behind the resulting large value of the exchange bias field and its good thermal stability. This mechanism for establishing the exchange bias in such a system can contribute towards the clarification of fundamental aspects of this exchange interaction.

This is a preview of subscription content, access via your institution

Access options

Buy this article

  • Purchase on Springer Link
  • Instant access to full article PDF
Buy now

Prices may be subject to local taxes which are calculated during checkout

Figure 1: Structural and magnetic characterization of the samples.
Figure 2: TEM and selective area diffraction (SAD) paired images of a Ta/IrMn/Ta sample.
Figure 3: Influence of the FeCo layer on the IrMn phase transition.
Figure 4: Magnetic characterization after crystallization of the IrMn layer.
Figure 5: Changing the direction of the magnetization in the FeCo layer as the crystalline phase of the IrMn layer develops.

Similar content being viewed by others

References

  1. Nogués, J. & Schuller, I. K. Exchange bias. J. Magn. Magn. Mater. 192, 203–232 (1999).

    Article  Google Scholar 

  2. Meiklejohn, W. H. & Bean, C. P. New magnetic anisotropy. Phys. Rev. 102, 1413–1414 (1956).

    Article  Google Scholar 

  3. Jungwirth, T., Marti, X., Wadley, P. & Wunderlich, J. Antiferromagnetic spintronics. Nat. Nanotech. 11, 231–241 (2016).

    Article  CAS  Google Scholar 

  4. Nogués, J. et al. Exchange bias in nanostructures. Phys. Rep. 442, 65–117 (2005).

    Article  Google Scholar 

  5. Dieny, B. et al. Giant magnetoresistive in soft ferromagnetic multilayers. Phys. Rev. B 43, 1297–1300 (1991).

    Article  CAS  Google Scholar 

  6. Kent, A. D. & Worledge, D. C. A new spin on magnetic memories. Nat. Nanotech. 10, 187–191 (2015).

    Article  CAS  Google Scholar 

  7. Nogués, J., Leighton, C. & Schuller, I. K. Correlation between antiferromagnetic interface coupling and positive exchange bias. Phys. Rev. B 61, 1315–1317 (2000).

    Article  Google Scholar 

  8. Samant, M. G., Lüning, J., Stöhr, J. & Parkin, S. S. P. Thermal stability of IrMn and MnFe exchange-biased magnetic tunnel junctions. Appl. Phys. Lett. 76, 3097–3099 (2000).

    Article  CAS  Google Scholar 

  9. van der Heijden, P. A. A. et al. Thermally assisted reversal of exchange biasing in NiO and FeMn based systems. Appl. Phys. Lett. 72, 492–494 (1998).

    Article  CAS  Google Scholar 

  10. Vallejo-Fernandez, G., Aley, N. P., Fernandez-Outon, L. E. & O’Grady, K. Control of the setting process in CoFe/IrMn exchange bias systems. J. Appl. Phys. 104, 033906 (2008).

    Article  Google Scholar 

  11. Imakita, K., Tusnoda, M. & Takahashi, M. Giant exchange anisotropy observed in Mn–Ir/Co–Fe bilayers containing ordered Mn3Ir phase. Appl. Phys. Lett. 85, 3812–3814 (2004).

    Article  CAS  Google Scholar 

  12. O’Grady, K., Fernandez-Outon, L. E. & Vallejo-Fernandez, G. A new paradigm for exchange bias in polycrystalline thin films. J. Magn. Magn. Mater. 322, 883–899 (2010).

    Article  Google Scholar 

  13. Thomas, L. & Negulescu, B. Metastable antiferromagnetic domain configurations in exchange biased bilayers. J. Appl. Phys. 93, 8606–8608 (2003).

    Article  CAS  Google Scholar 

  14. Paetzold, A. & Röll, K. Thermally activated self-alignment of exchange coupling in NiO/NiFe bilayers. J. Appl. Phys. 91, 7748–7750 (2002).

    Article  CAS  Google Scholar 

  15. Craig, B. et al. A model of the temperature dependence of exchange bias in coupled ferromagnetic/antiferromagnetic bilayers. J. Appl. Phys. 103, 07C102 (2008).

    Article  Google Scholar 

  16. Vallejo-Fernandez, G., Kaeswurm, B., Fernandez-Outon, L. E. & O’Grady, K. Effect of the ferromagnetic layer thickness on the blocking temperature in IrMn/CoFe exchange couples. IEEE Trans. Magn. 44, 2835–2838 (2008).

    Article  CAS  Google Scholar 

  17. Mougin, A. et al. Local manipulation and reversal of the exchange bias field by ion irradiation in FeNi/FeMn double layers. Phys. Rev. B 63, 060409(R) (2001).

    Article  Google Scholar 

  18. Ueltzhöffer, T. et al. Néel walls between tailored parallel-stripe domains in IrMn/CoFe exchange bias layers. J. Appl. Phys. 117, 123904 (2015).

    Article  Google Scholar 

  19. Martí, X. et al. Electrical measurement of antiferromagnetic moments in exchange-coupled IrMn/NiFe stacks. Phys. Rev. Lett. 108, 017201 (2012).

    Article  Google Scholar 

  20. Wang, Y. Y. et al. Room-temperature perpendicular exchange coupling and tunneling anisotropic magnetoresistance in an antiferromagnet-based tunnel junction. Phys. Rev. Lett. 109, 137201 (2012).

    Article  CAS  Google Scholar 

  21. Morales, R. et al. Exchange-bias phenomenon: the role of the ferromagnetic spin structure. Phys. Rev. Lett. 114, 097202 (2015).

    Article  CAS  Google Scholar 

  22. Avrami, M. Kinetics of phase change. II transformation-time relations for random distribution of nuclei. J. Chem. Phys. 8, 212–224 (1940).

    Article  CAS  Google Scholar 

  23. Kohn, A. et al. The antiferromagnetic structures of IrMn3 and their influence on exchange-bias. Sci. Rep. 3, 2412 (2013).

    Article  CAS  Google Scholar 

  24. El-Hilo, M., O’Grady, K. & Chantrell, R. V. The origin of non-linear ln(t) behaviour in the time dependence of magnetisation. J. Magn. Magn. Mater. 109, L164 (1992).

    Article  CAS  Google Scholar 

  25. Xi, H., Franzen, S., Mao, S. & White, R. M. Exchange bias relaxation in reverse magnetic fields. Phys. Rev. B 75, 014434 (2007).

    Article  Google Scholar 

  26. Fecioru-Morariu, M., Ali, S. R., Papusoi, C., Sperlich, M. & Güntherodt, G. Effects of Cu dilution in IrMn on the exchange bias of CoFe/IrMn bilayers. Phys. Rev. Lett. 99, 097206 (2007).

    Article  Google Scholar 

  27. Vallejo-Fernandez, G., Kaeswurm, B. & O’Grady, K. Defect and impurity effects in exchange bias systems. J. Appl. Phys. 109, 07D738 (2011).

    Article  Google Scholar 

  28. Ohldag, H. et al. Correlation between exchange bias and pinned interfacial spins. Phys. Rev. Lett. 91, 017203 (2003).

    Article  CAS  Google Scholar 

  29. Zhou, X. et al. Mapping motion of antiferromagnetic interfacial uncompensated magnetic moment in exchange-biased bilayers. Sci. Rep. 5, 9183 (2015).

    Article  CAS  Google Scholar 

  30. Wu, J. et al. Direct measurement of rotatable and frozen CoO spins in exchange bias system of CoO/Fe/Ag(001). Phys. Rev. Lett. 104, 217204 (2010).

    Article  CAS  Google Scholar 

  31. Bode, M. et al. Atomic spin structure of antiferromagnetic domain walls. Nat. Mater. 5, 477–481 (2006).

    Article  CAS  Google Scholar 

  32. Vallejo-Fernandez, G., Aley, N. P., Chapman, J. N. & O’Grady, K. Measurement of the attempt frequency in antiferromagnets. Appl. Phys. Lett. 97, 222505 (2010).

    Article  Google Scholar 

Download references

Acknowledgements

We thank K. O’Grady for his helpful discussions. This work has been funded by the Spanish Ministerio de Economía y Competitividad through the projects MAT2014-52477-C5-1-P and MAT2014-52477-C5-3-P and by the Spanish Consejo Social of the Universidad Politécnica de Madrid through the scholarship ‘Ayuda del Consejo Social para el Fomento de la formación y la Internacionalización de Doctorandos’, awarded for a three months internship at the University of York. V.K.L. thanks the funding support by EPSRC grant EP/K03278X/1. J.C. and J.L.F.C. thank support by MINECO through Projects FIS2016-78591-C3-1-R and SEV-2016-0686 and by Comunidad de Madrid through Project S2013/MIT-2850.

Author information

Authors and Affiliations

  1. Instituto de Sistemas Optoelectrónicos y Microtecnología-ISOM. Universidad Politécnica de Madrid, Avenida Complutense 30, 28040 Madrid, Spain

    A. Migliorini, C. Aroca & J. L. Prieto

  2. Department of Physics, University of York, York YO10 5DD, UK

    B. Kuerbanjiang, T. Huminiuc, G. Vallejo-Fernández & V. K. Lazarov

  3. SuperSTEM, STFC Daresbury Laboratories, Keckwick Lane, Warrington WA4 4AD, UK

    D. Kepaptsoglou

  4. IMN-Instituto de Micro y Nanotecnología, (CNM-CSIC), Isaac Newton 8, 28760 Tres Cantos, Madrid, Spain

    M. Muñoz

  5. IMDEA-Nanoscience, c/ Faraday, 9 Campus de Cantoblanco, 28049 Madrid, Spain

    J. L. F. Cuñado & J. Camarero

  6. DFMC and Instituto “Nicolás Cabrera”, Universidad Autónoma de Madrid, 28049 Madrid, Spain

    J. L. F. Cuñado & J. Camarero

  7. Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, 28049 Madrid, Spain

    J. Camarero

Authors
  1. A. Migliorini
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. B. Kuerbanjiang
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. T. Huminiuc
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. D. Kepaptsoglou
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. M. Muñoz
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. J. L. F. Cuñado
    View author publications

    You can also search for this author in PubMed Google Scholar

  7. J. Camarero
    View author publications

    You can also search for this author in PubMed Google Scholar

  8. C. Aroca
    View author publications

    You can also search for this author in PubMed Google Scholar

  9. G. Vallejo-Fernández
    View author publications

    You can also search for this author in PubMed Google Scholar

  10. V. K. Lazarov
    View author publications

    You can also search for this author in PubMed Google Scholar

  11. J. L. Prieto
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

A.M. deposited the samples and performed (or was strongly involved) in most of the experimental characterization. T.H. performed some of the crystallization experiments observed using electron microscopy. M.M. designed some of the experimental set-ups used for characterizations. J.L.F.C. and J.C. provided expertise and performed Kerr microscopy with A.M. C.A. was the first to suggest that a phase transition in the IrMn was probably behind the unusual behaviour of the samples. G.V.-F. helped with the magnetic characterization following the York protocol and performed the fitting displayed in Fig. 4d. V.K.L. and B.K. performed the TEM characterization with some of the specimens measured by D.K. J.L.P. directed the research and designed the sputtering system used for the deposition of the samples. J.L.P. wrote the manuscript with inputs from all the authors.

Corresponding author

Correspondence to J. L. Prieto.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

Supplementary Information (PDF 890 kb)

Supplementary Information

Supplementary Movie 1 (WMV 12681 kb)

Supplementary Information

Supplementary Movie 2 (WMV 37869 kb)

Supplementary Information

Supplementary Movie 3 (WMV 13150 kb)

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Migliorini, A., Kuerbanjiang, B., Huminiuc, T. et al. Spontaneous exchange bias formation driven by a structural phase transition in the antiferromagnetic material. Nature Mater 17, 28–35 (2018). https://doi.org/10.1038/nmat5030

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nmat5030

This article is cited by

Search

Advanced search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing