Abstract
Techniques that can produce patterns with nanoscale details on surfaces have a central role in the development of new electronic1,2,3, optical4,5,6 and magnetic7,8,9,10 devices and systems. High-energy ion irradiation can produce nanoscale patterns on ferromagnetic films by destroying the structure of layers or interfaces10,11,12,13,14,15,16,17,18, but this approach can damage the film and introduce unwanted defects13,14. Moreover, ferromagnetic nanostructures that have been patterned by ion irradiation often interfere with unpatterned regions through exchange interactions, which results in a loss of control over magnetization switching15,16,17,18. Here, we demonstrate that low-energy proton irradiation can pattern an array of 100-nm-wide single ferromagnetic domains by reducing [Co3O4/Pd]10 (a paramagnetic oxide) to produce [Co/Pd]10 (a ferromagnetic metal). Moreover, there are no exchange interactions in the final superlattice, and the ions have a minimal impact on the overall structure, so the interfaces between alternate layers of cobalt (which are 0.6 nm thick) and palladium (1.0 nm) remain intact. This allows the reduced [Co/Pd]10 superlattice to produce a perpendicular magnetic anisotropy that is stronger than that observed in the metallic [Co/Pd]10 superlattices we prepared for reference. We also demonstrate that our non-destructive approach can reduce CoFe2O4 to metallic CoFe.
This is a preview of subscription content, access via your institution
Access options
Subscribe to this journal
Receive 12 print issues and online access
$259.00 per year
only $21.58 per issue
Buy this article
- Purchase on Springer Link
- Instant access to full article PDF
Prices may be subject to local taxes which are calculated during checkout
Similar content being viewed by others
Change history
09 August 2012
In the version of this Letter originally published online, on page 1 'structure' was incorrectly used instead of 'texture' in the sentence "…and has a face-centred-cubic (fcc) (311) texture." Also an extraneous '1' appeared on page 2 in the sentence "Note that cobalt hydroxide is paramagnetic at room temperature and antiferromagnetic below ∼12 K." The authors also wish to correct some further problems: On page 2, the word 'glazing' should have been 'grazing' in the sentence "…cobalt hydroxide are observed under grazing incident synchronous X-ray scattering…". On page 4, the phrase 'and high coercivity' should not have appeared in the sentence "…the patterns demonstrate strong PMA — a squareness of unity — just as we find in…". In the first line of the Methods section, the phrase 'thermally oxidized' was missing in the sentence "Superlattices were deposited on a thermally oxidized Si(100) substrate using…". All these errors have now been corrected in all versions of the Letter.
References
Yusa, G., Muraki, K., Takashina, K., Hashimoto, K. & Hirayama, Y. Controlled multiple quantum coherences of nuclear spins in a nanometre-scale device. Nature 434, 1001–1005 (2005).
Bai, J., Zhong, X., Jiang, S., Huang, Y. & Duan, X. Graphene nanomesh. Nature Nanotech. 5, 190–194 (2010).
Lee, M-J. et al. A fast, high-endurance and scalable non-volatile memory device made from asymmetric Ta2O5– x/TaO2– x bilayer structures. Nature Mater. 10, 625–630 (2011).
Pavesi, L., Negro, L. D., Mazzoleni, C., Franzò, G. & Priolo, F. Optical gain in silicon nanocrystals. Nature 408, 440–444 (2000).
Nagpal, P., Lindquist, N. C., Oh, S-H. & Norris, D. J. Ultrasmooth patterned metals for plasmonics and metamaterials. Science 325, 594–597 (2009).
Shankar, S. S., Rizzello, L., Cingolani, R., Rinaldi, R. & Pompa, P. P. Micro/nanoscale patterning of nanostructured metal substrates for plasmonic applications. ACS Nano 3, 893–900 (2009).
Parkin, S. S. P., Hayashi, M. & Thomas, L. Magnetic domain-wall racetrack memory. Science 320, 190–194 (2008).
Mangin, S. et al. Current-induced magnetization reversal in nanopillars with perpendicular anisotropy. Nature Mater. 5, 210–215 (2006).
Kiselev, S. I. et al. Microwave oscillations of a nanomagnet driven by a spin-polarized current. Nature 425, 380–383 (2003).
Chappert, C. et al. Planar patterned magnetic media obtained by ion irradiation. Science 280, 1919–1922 (1998).
Rettner, C. T. et al. Magnetic characterization and recording properties of patterned Co70Cr18Pt12 perpendicular media. IEEE Trans. Magn. 38, 1725–1730 (2002).
McGrouther, D. & Chapman, J. N. Nanopatterning of a thin ferromagnetic CoFe film by focused-ion-beam irradiation. Appl. Phys. Lett. 87, 022507 (2005).
Terris, B. D. et al. Ion-beam patterning of magnetic films using stencil masks. Appl. Phys. Lett. 75, 403–405 (1999).
Fassbender, J., Ravelosona, D & Samson, Y. Tailoring magnetism by light-ion irradiation. J. Phys. D 37, R179–R196 (2004).
Suharyadi, E., Kato, T., Tsunashima, S. & Iwata, S. Magnetic properties of patterned Co/Pd nanostructures by e-beam lithography and Ga ion irradiation. IEEE Trans. Magn. 42, 2972–2974 (2006).
Parekh, V. et al. He+ ion irradiation study of continuous and patterned Co/Pd multilayers. J. Appl. Phys. 101, 083904 (2007).
Ajan, A. et al. Fabrication, magnetic, and R/W properties of nitrogen-ion-implanted Co/Pd and CoCrPt bit-patterned medium. IEEE Trans. Magn. 46, 2020–2023 (2010).
Kato, T. et al. Planar patterned media fabricated by ion irradiation into CrPt3 ordered alloy films. J. Appl. Phys. 105, 07C117 (2009).
Carcia, P. F. Perpendicular magnetic anisotropy in Pd/Co and Pt/Co thin‐film layered structures. J. Appl. Phys. 63, 5066–5073 (1988).
Engel, B. N. et al. Interface magnetic anisotropy in epitaxial superlattices. Phys. Rev. Lett. 67, 1910–1913 (1991).
Bean, C. P. & Livingston, J. D. Superparamagnetism. J. Appl. Phys. 30, S120–S129 (1959).
Martín, J. I., Nogués, J., Liu, K., Vicent, J. L. & Schuller, I. K. Ordered magnetic nanostructures: fabrication and properties. J. Magn. Magn. Mater. 256, 449–501 (2003).
Menéndez, E. et al. Direct magnetic patterning due to the generation of ferromagnetism by selective ion irradiation of paramagnetic FeAl alloys. Small 5, 229–234 (2009).
Bernas, H. et al. Ordering intermetallic alloys by ion irradiation: a way to tailor magnetic media. Phys. Rev. Lett. 91, 077203 (2003).
Shaw, J. M. et al. Effect of microstructure on magnetic properties and anisotropy distributions in Co/Pd thin films and nanostructures. Phys. Rev. B 80, 184419 (2009).
Thompson, M. W. Defects and Radiation Damage in Metals (Cambridge Univ. Press, 1969).
Webb, B. C. & Schultz, S. Detection of the magnetization reversal of individual interacting single-domain particles within Co–Cr columnar thin-films. IEEE Trans. Magn. 24, 3006–3008 (1988).
Schumacher, F. On the modification of the Kondorsky function. J. Appl. Phys. 70, 3184–3187 (1991).
Sharrock, M. P. & Mckinney, J. T. Kinetic effects in coercivity measurements. IEEE Trans. Magn. 17, 3020–3022 (1981).
Thomson, T., Hu, G. & Terris, B. D. Intrinsic distribution of magnetic anisotropy in thin films probed by patterned nanostructures. Phys. Rev. Lett. 96, 257204 (2006).
Acknowledgements
The authors thank E. Sullivan, Y. Jo, D.R. Lee, H-J. Shin, H.H. Lee, K-H. Yoo, M-H. Cho, D-H. Ko, I. Sohn, T. Emery, S-J. Park and M. Ahn for help with measurements and discussions. The authors also thank H. Youn and C-Y. Chung (Park System Corporation) for their support in observing magnetic images using MFM, and T.W. Lee (RIAM) for his support with XRD and XRR measurements. This research was supported in part by the Basic Science Research Program (2011-0003263), the Pioneer Research Center Program (2011-000-2116) and the Center for Nanoscale Mechatronics and Manufacturing (which is one of the 21st Century Frontier Research Programs (2011K000243) funded by the Korean Ministry of Education, Science and Technology).
Author information
Authors and Affiliations
Contributions
S.Ki. and J.H. conceived and designed the study. S.Ki. fabricated all patterns and carried out experiments, with the help of J.H. Contributions to the measurements were made by S.Ka., S.L., J.K., J.S. and M.K. All authors contributed to discussions regarding the research. S.Ki. and J.H. wrote the manuscript.
Corresponding author
Ethics declarations
Competing interests
The authors declare no competing financial interests.
Supplementary information
Supplementary information
Supplementary information (PDF 776 kb)
Rights and permissions
About this article
Cite this article
Kim, S., Lee, S., Ko, J. et al. Nanoscale patterning of complex magnetic nanostructures by reduction with low-energy protons. Nature Nanotech 7, 567–571 (2012). https://doi.org/10.1038/nnano.2012.125
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1038/nnano.2012.125
This article is cited by
-
Influence of proton irradiation on the magnetic properties of two-dimensional Ni(II) molecular magnet
Scientific Reports (2023)
-
Nanopatterning reconfigurable magnetic landscapes via thermally assisted scanning probe lithography
Nature Nanotechnology (2016)
-
Formation of Magnetic Anisotropy by Lithography
Scientific Reports (2016)
-
Direct Depth- and Lateral- Imaging of Nanoscale Magnets Generated by Ion Impact
Scientific Reports (2015)
-
Magnetic patterning: local manipulation of the intergranular exchange coupling via grain boundary engineering
Scientific Reports (2015)