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Nanocavity optomechanical torque magnetometry and radiofrequency susceptometry


Nanophotonic optomechanical devices allow the observation of nanoscale vibrations with a sensitivity that has dramatically advanced the metrology of nanomechanical structures1,2,3,4,5,6,7,8,9 and has the potential to impact studies of nanoscale physical systems in a similar manner10,11. Here we demonstrate this potential with a nanophotonic optomechanical torque magnetometer and radiofrequency (RF) magnetic susceptometer. Exquisite readout sensitivity provided by a nanocavity integrated within a torsional nanomechanical resonator enables observations of the unique net magnetization and RF-driven responses of single mesoscopic magnetic structures in ambient conditions. The magnetic moment resolution is sufficient for the observation of Barkhausen steps in the magnetic hysteresis of a lithographically patterned permalloy island12. In addition, significantly enhanced RF susceptibility is found over narrow field ranges and attributed to thermally assisted driven hopping of a magnetic vortex core between neighbouring pinning sites13. The on-chip magnetosusceptometer scheme offers a promising path to powerful integrated cavity optomechanical devices for the quantitative characterization of magnetic micro- and nanosystems in science and technology.

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Figure 1: Split-beam nanocavity.
Figure 2: Measurement set-up and spectral response.
Figure 3: Magnetic hysteresis of the permalloy island.
Figure 4: Enhanced room-temperature magnetic susceptibility at Barkhausen steps.


  1. 1

    Li, M. et al. Harnessing optical forces in integrated photonic circuits. Nature 456, 480–484 (2008).

    CAS  Article  Google Scholar 

  2. 2

    Liu, Y., Miao, H., Aksyuk, V. & Srinivasan, K. Wide cantilever stiffness range cavity optomechanical sensors for atomic force microscopy. Opt. Express 20, 18268–18280 (2012).

    CAS  Article  Google Scholar 

  3. 3

    Anetsberger, G. et al. Measuring nanomechanical motion with an imprecision below standard quantum limit. Phys. Rev. A 82, 061804 (2010).

    Article  Google Scholar 

  4. 4

    Krause, A. G., Winger, M., Blasius, T. D., Lin, W. & Painter, O. A high-resolution microchip optomechanical accelerometer. Nat. Photon. 6, 768–772 (2012).

    CAS  Article  Google Scholar 

  5. 5

    Kim, P. H. et al. Nanoscale torsional optomechanics. Appl. Phys. Lett. 102, 053102 (2013).

    Article  Google Scholar 

  6. 6

    Wu, M. et al. Dissipative and dispersive optomechanics in a nanocavity torque sensor. Phys. Rev. X 4, 021052 (2014).

    Google Scholar 

  7. 7

    Li, H. & Li, M. Optomechanical photon shuttling between photonic cavities. Nat. Nano. 9, 913–919 (2014).

    Article  Google Scholar 

  8. 8

    Chan, J. et al. Laser cooling of a nanomechanical oscillator into its quantum ground state. Nature 478, 89–92 (2011).

    CAS  Article  Google Scholar 

  9. 9

    Zhang, X., Zou, C. L., Jiang, L. & Tang, H. X. Cavity magnomechanics. Sci. Adv. 2, 1501286 (2016).

    Article  Google Scholar 

  10. 10

    Rugar, D., Budakian, R., Mamin, H. & Chui, B. Single spin detection by magnetic resonance force microscopy. Nature 430, 329–332 (2004).

    CAS  Article  Google Scholar 

  11. 11

    Bleszynski-Jayich, A. C. et al. Persistent currents in normal metal rings. Science 326, 272–275 (2009).

    CAS  Article  Google Scholar 

  12. 12

    Burgess, J. A. J. et al. Quantitative magnetomechanical detection and control of the Barkhausen effect. Science 339, 1051–1054 (2013).

    CAS  Article  Google Scholar 

  13. 13

    Compton, R. L. & Crowell, P. A. Dynamics of a pinned magnetic vortex. Phys. Rev. Lett. 97, 137202 (2006).

    CAS  Article  Google Scholar 

  14. 14

    Moreland, J. Micromechanical instruments for ferromagnetic measurements. J. Phys. D 36, R39–R51 (2003).

    CAS  Article  Google Scholar 

  15. 15

    Lim, S.-H. et al. Magneto-mechanical investigation of spin dynamics in magnetic multilayers. Europhys. Lett. 105, 37009 (2014).

    Article  Google Scholar 

  16. 16

    Davis, J. P. et al. Nanotorsional resonator torque magnetometry. Appl. Phys. Lett. 96, 072513 (2010).

    Article  Google Scholar 

  17. 17

    Losby, J. E. et al. Nanomechanical AC susceptometry of an individual mesoscopic ferrimagnet. Solid State Comm. 198, 3–6 (2014).

    CAS  Article  Google Scholar 

  18. 18

    Firdous, T. et al. Nanomechanical torque magnetometry of an individual aggregate of 350 nanoparticles. Can. J. Phys. 93, 1–5 (2015).

    Article  Google Scholar 

  19. 19

    Ascoli, C. et al. Micromechanical detection of magnetic resonance by angular momentum absorption. Appl. Phys. Lett. 69, 3920–3922 (1996).

    CAS  Article  Google Scholar 

  20. 20

    Losby, J. E. et al. Torque-mixing magnetic resonance spectroscopy. Science 350, 798–801 (2015).

    CAS  Article  Google Scholar 

  21. 21

    Forstner, S. et al. Ultrasensitive optomechanical magnetometry. Adv. Mater. 26, 6348–6353 (2014).

    CAS  Article  Google Scholar 

  22. 22

    Hryciw, A. C. & Barclay, P. E. Optical design of split-beam photonic crystal nanocavities. Opt. Lett. 38, 1612–1614 (2013).

    Article  Google Scholar 

  23. 23

    Hryciw, A. C., Wu, M., Khanaliloo, B. & Barclay, P. E. Tuning of nanocavity optomechanical coupling using a near-field fiber probe. Optica 2, 491–496 (2015).

    CAS  Article  Google Scholar 

  24. 24

    Rigue, J., Chrischon, D., de Andrade, A. M. H. & Carara, M. A torque magnetometer for thin films applications. J. Magn. Magn. Mater. 324, 1561–1564 (2012).

    CAS  Article  Google Scholar 

  25. 25

    Losby, J. E. et al. Nanomechanical torque magnetometry of permalloy cantilevers. J. Appl. Phys. 108, 123910 (2010).

    Article  Google Scholar 

  26. 26

    Cowburn, R. P., Koltsov, D. K., Adeyeye, A. O., Welland, M. E. & Tricker, D. M. Single-domain circular nanomagnets. Phys. Rev. Lett 82, 1042–1045 (1999).

    Article  Google Scholar 

  27. 27

    Abu-Libdeh, N. & Venus, D. Dynamics of domain growth driven by dipolar interactions in a perpendicularly magnetized ultrathin film. Phys. Rev. B 81, 195416 (2010).

    Article  Google Scholar 

  28. 28

    Kim, P. H., Hauer, B. D., Doolin, C., Souris, F. & Davis, J. P. Approaching the standard quantum limit of mechanical torque sensing. Preprint at (2016).

  29. 29

    Safavi-Naeini, A. et al. Squeezed light from a silicon micromechanical resonator. Nature 500, 185–189 (2013).

    CAS  Article  Google Scholar 

  30. 30

    Rahm, M., Biberger, J., Umasky, V. & Weiss, D. Vortex pinning at individual defects in magnetic nanodisks. J. Appl. Phys. 93, 7429–7431 (2003).

    CAS  Article  Google Scholar 

  31. 31

    Tetienne, J.-P. et al. Nanoscale imaging and control of domain-wall hopping with a nitrogen-vacancy center microscope. Science 344, 1366–1369 (2014).

    CAS  Article  Google Scholar 

  32. 32

    Rugar, D. et al. Proton magnetic resonance imaging using a nitrogen–vacancy spin sensor. Nat. Nano. 10, 120–124 (2015).

    CAS  Article  Google Scholar 

  33. 33

    Diao, Z. et al. Stiction-free fabrication of lithographic nanostructures on resist-supported nanomechanical resonators. J. Vac. S. Tech. B 31, 051805 (2013).

    Article  Google Scholar 

  34. 34

    Vansteenkiste, A. et al. The design and verification of MuMax3. AIP Adv. 4, 107133 (2014).

    Article  Google Scholar 

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This work is supported by the Natural Science and Engineering Research Council of Canada, Canada Research Chairs, the Canada Foundation for Innovation and Alberta Innovates Technology Futures. Many thanks to A. Hryciw, M. Mitchell, M. Belov and D. Fortin for their technical contributions. We also thank the staff of the nanofabrication facilities at the University of Alberta and at the National Institute for Nanotechnology as well as the machinists at the University of Calgary Science Workshop for their technical support.

Author information




P.E.B. and M.R.F. conceived and supervised the project. M.W. and N.L.-Y.W. designed and fabricated the devices. N.L.-Y.W. imaged the devices. M.W. set up the measurement equipment, including the fibre taper. M.W., N.L.-Y.W. and T.F. performed measurements on the device. M.W., N.L.-Y.W., T.F. and F.F. analysed the data. M.W. and N.L.-Y.W. prepared the figures. F.F. and T.F. contributed simulations to the manuscript. F.F. helped with the theoretical framework for the RF susceptibility mixing scheme in the supplementary material. J.E.L. provided guidance and technical assistance with the instrumentation and measurements. All the co-authors contributed to and proofread the manuscript.

Corresponding authors

Correspondence to Mark R. Freeman or Paul E. Barclay.

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The authors declare no competing financial interests.

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Wu, M., Wu, NY., Firdous, T. et al. Nanocavity optomechanical torque magnetometry and radiofrequency susceptometry. Nature Nanotech 12, 127–131 (2017).

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