Magnetic resonance force microscopy in fast-relaxing spins using a frequency-modulation mode detection method

Lee, SangGap; Won, Soonho; Saun, Seung-Bo; Lee, Soonchil

doi:10.1088/0957-4484/18/37/375505

Cited by 5 publications

(3 citation statements)

References 34 publications

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“…Cyclic adiabatic inversion (15) is likewise inapplicable because it relies on continuous spin locking. Saturating the sample spins cyclically is another approach to creating a distinguishable signal (20,21). To achieve high sensitivity, spin magnetization should be modulated at the cantilever's resonance frequency.…”

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confidence: 99%

Scanned-probe detection of electron spin resonance from a nitroxide spin probe

Moore

Lee

Hickman

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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We report an approach that extends the applicability of ultrasensitive force-gradient detection of magnetic resonance to samples with spin-lattice relaxation times (T 1 ) as short as a single cantilever period. To demonstrate the generality of the approach, which relies on detecting either cantilever frequency or phase, we used it to detect electron spin resonance from a T 1 = 1 ms nitroxide spin probe in a thin film at 4.2 K and 0.6 T. By using a custom-fabricated cantilever with a 4 μm-diameter nickel tip, we achieve a magnetic resonance sensitivity of 400 Bohr magnetons in a 1 Hz bandwidth. A theory is presented that quantitatively predicts both the lineshape and the magnitude of the observed cantilever frequency shift as a function of field and cantilever-sample separation. Good agreement was found between nitroxide T 1 's measured mechanically and inductively, indicating that the cantilever magnet is not an appreciable source of spin-lattice relaxation here. We suggest that the new approach has a number of advantages that make it well suited to push magnetic resonance detection and imaging of nitroxide spin labels in an individual macromolecule to single-spin sensitivity.MRFM | ESR | TEMPAMINE | mechanically detected magnetic resonance | molecular structure imaging A generally applicable approach for determining the tertiary structure of an individual macromolecule in vitro at angstrom or subangstrom resolution would create exciting opportunities for answering many longstanding questions in molecular biology. For macromolecules too large to characterize by NMR or X-ray diffraction, the tertiary structure of proteins (1-3), nucleic acids (4, 5), and biomolecular assemblies (6, 7) can be explored by using inductively-detected electron spin resonance (ESR) to measure distances between pairs of attached spin labels (2-5, 7, 8). These studies, however, require bulk quantities of sample (9) and demand multiple experiments with spin labels attached to different locations in the target macromolecule. Mechanical detection and imaging of single-electron spins has been demonstrated, in E centers in gamma-irradiated quartz (10), and it is natural to explore applying magnetic resonance force microscopy (MRFM) (11-15) to map the locations of individual spin labels attached to a single biomacromolecule.The ultimate limit of imaging resolution in MRFM is set by the intrinsic linewidth of the resonance and the applied magnetic field gradient. For a 0.1 mT homogeneous linewidth, typical of the organic radical studied here, a gradient of 4 × 10 6 T/m allows selective excitation of individual spin labels only 0.025 nm apart. A magnetic field gradient this large has recently been demonstrated in an MRFM experiment by using ferromagnetic pillars fabricated by electron-beam lithography (15). The force sensitivity required to detect single electrons in this gradient is 40 aN, above the minimum detectable force (in 1 Hz bandwidth) of 5 − 10 aN reported for a high-compliance cantilever operated with its metalized leading edge above ...

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confidence: 99%

Scanned-probe detection of electron spin resonance from a nitroxide spin probe

Moore

Lee

Hickman

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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“…A final set of FM-MRFM protocols considered here are those based on force gradients and cyclic saturation of sample magnetization, applicable to fast-relaxing spins with T 1 ≤ T and used so far to detect ESR. 26,27,29,31 These frequency-shift experiments are not obviously related; here we show that all three classes of experiments can nevertheless be described by a single unified formalism.…”

Section: Introductionmentioning

confidence: 67%

Unified picture of cantilever frequency shift measurements of magnetic resonance

2012

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We report a unified framework describing all existing protocols for spin manipulation and signal creation in frequency-modulation magnetic resonance force microscopy using classical perturbation theory. The framework is well suited for studying the dependence of the frequency shift on the cantilever amplitude via numerical simulation. We demonstrate the formalism by recovering an exact result for a single spin signal and by simulating, for the first time as a function of cantilever amplitude, the frequency shift due to a volume of noninteracting spins inverted by an adiabatic rapid passage. We show that an optimal cantilever amplitude exists that maximizes the signal. Our findings suggest that understanding the amplitude dependence of the spin signal will be important for designing future high-sensitivity experiments.

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“…What was actually measured by the interferometer to detect the resonance was not the cantilever deflection but the shift of the cantilever resonance frequency under external force 14 15 16 . The details of this measurement scheme are also described in our previous work 22 . The cantilever was driven to vibrate near its mechanical resonance frequency at a constant amplitude level by feedback circuits.…”

Section: Methodsmentioning

confidence: 99%

NMR Spectroscopy for Thin Films by Magnetic Resonance Force Microscopy

Won

Saun

Lee

et al. 2013

Sci Rep

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Nuclear magnetic resonance (NMR) is a fundamental research tool that is widely used in many fields. Despite its powerful applications, unfortunately the low sensitivity of conventional NMR makes it difficult to study thin film or nano-sized samples. In this work, we report the first NMR spectrum obtained from general thin films by using magnetic resonance force microscopy (MRFM). To minimize the amount of imaging information inevitably mixed into the signal when a gradient field is used, we adopted a large magnet with a flat end with a diameter of 336 μm that generates a homogeneous field on the sample plane and a field gradient in a direction perpendicular to the plane. Cyclic adiabatic inversion was used in conjunction with periodic phase inversion of the frequency shift to maximize the SNR. In this way, we obtained the 19F NMR spectrum for a 34 nm-thick CaF2 thin film.

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Magnetic resonance force microscopy in fast-relaxing spins using a frequency-modulation mode detection method

Cited by 5 publications

References 34 publications

Scanned-probe detection of electron spin resonance from a nitroxide spin probe

Scanned-probe detection of electron spin resonance from a nitroxide spin probe

Unified picture of cantilever frequency shift measurements of magnetic resonance

NMR Spectroscopy for Thin Films by Magnetic Resonance Force Microscopy

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