Quantitative Magneto-Mechanical Detection and Control of the Barkhausen Effect

Burgess, Jacob A. J.; Fraser, Alastair; Sani, Fatemeh Fani; Vick, D.; Hauer, Bradley; Davis, J. P.; Freeman, M. R.

doi:10.1126/science.1231390

Cited by 89 publications

(106 citation statements)

References 35 publications

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“…The high energy density of vortex cores make them susceptible to pinning at imperfections (surface roughness and grain boundaries) in the polycrystalline island. With diameters on the order of ten nanometers, the cores finely probe the magnetic landscape as their positions change with applied field [12]. Pinning and depinning events are captured as Barkhausen steps, with notable reductions in slope of the hysteresis curve seen whilst cores are pinned.…”

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confidence: 99%

“…The high detection sensitivity of resonant nanomechanical torque sensors has allowed for minimally-invasive observations of magnetostatic interactions and hysteresis in a variety of magnetic materials including thin films [15], mesoscale confined geometries that are deposited [16] or epitaxially grown [17], and small aggregates of nanoparticles [18]. Going beyond the static limit, nanomechanical torque magnetometry has been extended to timescales allowing for detection of slow thermally-activated dynamics [12], AC susceptibility [17], and magnetic resonance [19,20].…”

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confidence: 99%

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Nanocavity optomechanical torque magnetometry and radiofrequency susceptometry

Wu¹,

Wu²,

Firdous³

et al. 2016

Nature Nanotech

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Nanophotonic optomechanical devices allow observation of nanoscale vibrations with sensitivity that has dramatically advanced metrology of nanomechanical structures [1][2][3][4][5][6][7][8][9] and has the potential to impact studies of nanoscale physical systems in a similar manner [10,11]. 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 observation of Barkhausen steps in the magnetic hysteresis of a lithographically patterned permalloy island [12]. 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 neighboring pinning sites [13]. The on-chip magneto-susceptometer scheme offers a promising path to powerful integrated cavity optomechanical devices for quantitative characterization of magnetic micro-and nanosystems in science and technology.Torque magnetometry has seen recent resurgence owing to miniaturization of mechanical devices [14]. The high detection sensitivity of resonant nanomechanical torque sensors has allowed for minimally-invasive observations of magnetostatic interactions and hysteresis in a variety of magnetic materials including thin films [15], mesoscale confined geometries that are deposited [16] or epitaxially grown [17], and small aggregates of nanoparticles [18]. Going beyond the static limit, nanomechanical torque magnetometry has been extended to timescales allowing for detection of slow thermally-activated dynamics [12], AC susceptibility [17], and magnetic resonance [19,20].This powerful technique relies upon detection of the deflection of a mechanical element by angular momentum transfer originating from magnetic torques τ = µ 0 m×H, generated as the magnetic moments in the system, m, experience an orthogonally-directed component of the applied magnetic field, H. So far, improvements to torque magnetometers have been driven primarily by enhancements to the response of nanomechanical resonators resulting from their low mass and high mechanical quality factor (Q m ). Readout of magnetically driven motion has involved detection through free-space optical interferometric methods with very low optical quality factor (Q o ≈ 1) Fabry-Perot cavities formed between the nanomechanical resonator its supporting substrate [16]. However, as device dimensions scale down, and the number of magnetic spins become too small or the dynamics too fast, the mechanical deflections become more difficult to detect. Migration to a more sensitive readout scheme is essential. The integration of a nanoscale optical cavity offers a natural path for improvement. Nanocavity-optomechanical devices enhance mechanarXiv:...

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confidence: 99%

mentioning

confidence: 99%

Nanocavity optomechanical torque magnetometry and radiofrequency susceptometry

Wu¹,

Wu²,

Firdous³

et al. 2016

Nature Nanotech

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“…However, for a complete analysis, also thermal fluctuations have to be taken into account. 15 For small motions around the equilibrium position, X 0 , the frequency of the vortex oscillation can be obtained from the linearized equation. Figure 4 shows the frequency as a function of applied magnetic in-plane field.…”

Section: A Analytical Modelmentioning

confidence: 99%

Vortex dynamics in Co-Fe-B magnetic tunnel junctions in presence of defects

Kuepferling

Zullino

Sola

et al. 2015

Journal of Applied Physics

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We investigate the frequency of thermally excited vortex oscillations in Co-Fe-B magnetic tunnel\ud junction (MTJ) pillars in the presence of defects. Under a variable in-plane magnetic field, a characteristic\ud behavior is observed: the frequency oscillates from a maximum at certain field values to a\ud steep minimum, which tends towards zero frequency. These frequency variations are described\ud qualitatively well by an analytical model based on the Thiele equation taking into account a single\ud Gaussian pinning potential. It is thus possible to calculate the in-plane depinning field for certain\ud pinning potential parameters. For steep potentials, the depinning is hysteretic and jumps between\ud the pinned and unpinned regime occur due to the presence of an energy barrier. A sharp frequency\ud minimum occurs at an applied field, where a large flat region in the energy landscape is present.\ud From the experiments, the pinning potentials are estimated to be between 0.2eV and 0.4eV. We\ud also perform micromagnetic simulations of the vortex oscillations in the presence of a distribution\ud of pinning centers. The simulations confirm the validity of the Thiele-approach showing that the\ud vortex remains sufficiently rigid

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“…It is confined to the vortex core (VC) of diameter comparable to the material exchange length 7,8 . Recent experimental works reported evidence that the dynamics of the VC is affected by the presence of structural defects in the sample [9][10][11][12] . This is indicative of the behavior similar to that of the elastic string in a random pinning potential 13 , with the finite elasticity of the vortex provided by the exchange interaction 14 .…”

Section: Introductionmentioning

confidence: 99%

Josephson Junction with a Magnetic Vortex

Zarzuela

Chudnovsky

Tejada

2015

J Supercond Nov Magn

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We have studied Josephson tunneling through a circularly polarized micron or submicron-size disk of a soft ferromagnetic material. Such a disk contains a vortex that exhibits rich classical dynamics and has recently been proposed as a tool to study quantum dynamics of the nanoscale vortex core. The change in the Josephson current that is related to a tiny displacement of the vortex core has been computed analytically and plotted numerically for permalloy disks used in experiments. It is shown that a Josephson junction with a magnetic disk in the vortex state can be an interesting physical system that may be used to measure the nanoscale motion of the magnetic vortex.

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Quantitative Magneto-Mechanical Detection and Control of the Barkhausen Effect

Cited by 89 publications

References 35 publications

Nanocavity optomechanical torque magnetometry and radiofrequency susceptometry

Nanocavity optomechanical torque magnetometry and radiofrequency susceptometry

Vortex dynamics in Co-Fe-B magnetic tunnel junctions in presence of defects

Josephson Junction with a Magnetic Vortex

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