Eric W Moore

Cornell University, Итак, New York, United States

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Publications (11)37 Total impact

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    ABSTRACT: We introduce a spin-modulation protocol for force-gradient detection of magnetic resonance that enables the real-time readout of longitudinal magnetization in an electron spin resonance experiment involving fast-relaxing spins. We applied this method to observe a prompt change in longitudinal magnetization following the microwave irradiation of a nitroxide-doped perdeuterated polystyrene film having an electron spin-lattice relaxation time of [Formula: see text]. The protocol allowed us to discover a large, long-lived cantilever frequency shift. Based on its magnitude, lifetime, and field dependence, we tentatively attribute this persistent signal to deuteron spin magnetization created via transfer of polarization from nitroxide spins.
    Applied Physics Letters 04/2013; 102(13):132404. DOI:10.1063/1.4795018 · 3.52 Impact Factor
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    ABSTRACT: In-plane to out-of-plane magnetization switching in a single nickel nanorod affixed to an attonewton-sensitivity cantilever was studied at cryogenic temperatures. We observe multiple sharp, simultaneous transitions in cantilever frequency, dissipation, and frequency jitter associated with magnetic switching through distinct intermediate states. These findings suggest a new route for detecting magnetic fields at the nanoscale. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3699363]
    Journal of Applied Physics 04/2012; 111(8):83911-839117. DOI:10.1063/1.3699363 · 2.19 Impact Factor
  • Sanggap Lee · Eric W Moore · John A Marohn
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    ABSTRACT: 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.
    Physical Review B 04/2012; 85(16):165447-165453. DOI:10.1103/PhysRevB.85.165447 · 3.74 Impact Factor
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    ABSTRACT: The authors report a method for rapidly prototyping attonewton-sensitivity cantilevers with custom-fabricated tips and illustrate the method by preparing tips consisting of a magnetic nanorod overhanging the leading edge of the cantilevers. Micron-long nickel nanorods with widths of 120-220 nm were fabricated on silicon chips by electron beam lithography, deposition, and lift-off. Each silicon chip, with its integral nanomagnet, was attached serially to a custom-fabricated attonewton-sensitivity cantilever using focused ion beam manipulation. The magnetic nanorod tips were prepared with and without an alumina capping layer, and the minimum detectable force and tip magnetic moment of the resulting cantilevers was characterized by cantilever magnetometry. The results indicate that this serial but high-yield approach is an effective way to rapidly prepare and characterize magnetic tips for the proposed single-electron-spin and single-proton magnetic resonance imaging experiments. The approach also represents a versatile route for affixing essentially any vacuum-compatible sample to the leading edge of an attonewton-sensitivity cantilever.
    Journal of vacuum science & technology. B, Microelectronics and nanometer structures: processing, measurement, and phenomena: an official journal of the American Vacuum Society 05/2011; 29(3):32001. DOI:10.1116/1.3581102 · 1.36 Impact Factor
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    ABSTRACT: Torque magnetometry, using attonewton-sensitivity cantilevers, is extremely sensitive to both the average magnetic moment and magnetization fluctuations within a small magnetic tip. Operating at T = 4 : K with such a system, we study in-plane to out-of-plane magnetization switching in a single, electron beam lithographically defined nickel nanorod, of radius r 50 : nm. Numerous, simultaneous, peaks are visible in cantilever frequency, dissipation and jitter as well as Barkhausen like steps. A analytic model is developed that achieves order of magnitude agreement with the frequency and dissipation peaks.
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    ABSTRACT: We have batch-fabricated cantilevers with ∼100 nm diameter nickel nanorod tips and force sensitivities of a few attonewtons at 4.2 K. The magnetic nanorods were engineered to overhang the leading edge of the cantilever, and consequently the cantilevers experience what we believe is the lowest surface noise ever achieved in a scanned probe experiment. Cantilever magnetometry indicated that the tips were well magnetized, with a ≤ 20 nm dead layer; the composition of the dead layer was studied by electron microscopy and electron energy loss spectroscopy. In what we believe is the first demonstration of scanned probe detection of electron-spin resonance from a batch-fabricated tip, the cantilevers were used to observe electron-spin resonance from nitroxide spin labels in a film via force-gradient-induced shifts in cantilever resonance frequency. The magnetic field dependence of the magnetic resonance signal suggests a nonuniform tip magnetization at an applied field near 0.6 T.
    ACS Nano 11/2010; 4(12):7141-50. DOI:10.1021/nn101577t · 12.88 Impact Factor
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    ABSTRACT: We introduce and demonstrate a method of measuring small force gradients acting on a harmonic oscillator in which the force-gradient signal of interest is used to parametrically up-convert a forced oscillation below resonance into an amplitude signal at the oscillator's resonance frequency. The approach, which we demonstrate in a mechanically detected electron spin resonance experiment, allows the force-gradient signal to evade detector frequency noise by converting a slowly modulated frequency signal into an amplitude signal.
    Applied Physics Letters 07/2010; 97(4). DOI:10.1063/1.3465906 · 3.52 Impact Factor
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    ABSTRACT: Magnetic resonance force microscopy is a promising route to 3-dimensional nanoscale imaging of organic materials due to its high sensitivity and isotopic specificity. Labeling of proteins, DNA and biomolecular assemblies with free radical labels for inductive detection are well established techniques, although many of these radical's relaxation times are too short to support previously demonstrated techniques for single electron detection by magnetic resonance force microscopy. We report on our efforts toward sub-single electron sensitivity on organic radicals using batch fabricated 100 nm nickel nanorod tipped ultrasensitive cantilevers.
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    ABSTRACT: 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 microm-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.
    Proceedings of the National Academy of Sciences 12/2009; 106(52):22251-6. DOI:10.1073/pnas.0908120106 · 9.81 Impact Factor
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    ABSTRACT: Nitroxide spin labels are widely used in electron spin resonance studies of biological and polymeric systems. Magnetic resonance force microscopy (MRFM) is a magnetic resonance technique that couples the high spatial resolution of a scanning probe microscope with the species selectivity of magnetic resonance. We report on our investigations of 4-amino TEMPO, a nitroxide spin label, by force-gradient MRFM. Our microscope operates at high vacuum in liquid helium, using a custom fabricated ultra-soft silicon cantilever in the magnet-on-cantilever geometry. An 18 GHz gap coupled microstripline resonator supplies the transverse field.
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    ABSTRACT: Nitroxide spin labels, such as 4-amino TEMPO can be used to as environmental, conformal and structural probes in biological and polymer systems. We report on our efforts to detect electron spin resonance of 4-amino TEMPO in a polymer matrix using the magnetic resonance force microscope as a proof of concept for future experiments on spin labeled proteins. Our microscope operates at high vacuum and low temperature, using a custom fabricated single crystal silicon cantilever in the magnet-on-cantilever geometry. The applied field is provided by a microstripline resonator at 18 GHz.