Laser Modulation of Superconductivity in a Cryogenic Wide-field Nitrogen-Vacancy Microscope

Lillie, S. E.; Broadway, David A.; Dontschuk, Nikolai; Scholten, Sam C.; Johnson, Brett C.; Wolf, Sebastian; Rachel, Stephan; Hollenberg, Lloyd C. L.

doi:10.1021/acs.nanolett.9b05071

Cited by 40 publications

(42 citation statements)

References 49 publications

(101 reference statements)

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“…The domain evolution measurement in a three-layer and four-layer sample indicates nearly rectangular hysteresis loops with higher coercive fields than domain #2 in the bilayer sample. Indeed, the influence of laser heating need to be determined as in previous works using NV center 31,50 . We show that the laser heating effect is negligible in this work by measuring both the domain structure and magnetization at various laser power in a three-layer CrBr 3 sample.…”

Section: Discussionmentioning

confidence: 99%

Magnetic domains and domain wall pinning in atomically thin CrBr3 revealed by nanoscale imaging

et al. 2021

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The emergence of atomically thin van der Waals magnets provides a new platform for the studies of two-dimensional magnetism and its applications. However, the widely used measurement methods in recent studies cannot provide quantitative information of the magnetization nor achieve nanoscale spatial resolution. These capabilities are essential to explore the rich properties of magnetic domains and spin textures. Here, we employ cryogenic scanning magnetometry using a single-electron spin of a nitrogen-vacancy center in a diamond probe to unambiguously prove the existence of magnetic domains and study their dynamics in atomically thin CrBr3. By controlling the magnetic domain evolution as a function of magnetic field, we find that the pinning effect is a dominant coercivity mechanism and determine the magnetization of a CrBr3 bilayer to be about 26 Bohr magnetons per square nanometer. The high spatial resolution of this technique enables imaging of magnetic domains and allows to locate the sites of defects that pin the domain walls and nucleate the reverse domains. Our work highlights scanning nitrogen-vacancy center magnetometry as a quantitative probe to explore nanoscale features in two-dimensional magnets.

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Section: Discussionmentioning

confidence: 99%

Magnetic domains and domain wall pinning in atomically thin CrBr3 revealed by nanoscale imaging

et al. 2021

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“…Each pixel of the camera records an ODMR spectrum, allowing a B NV map of the sample to be generated. The diamond‐sample assembly is placed in a cryostat allowing measurements from 4 to 300 K. [ 26 ]…”

Section: Figurementioning

confidence: 99%

Imaging Domain Reversal in an Ultrathin Van der Waals Ferromagnet

et al. 2020

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2D van der Waals materials exhibiting intrinsic magnetic order have attracted enormous interest in the last few years. [1-5] However, despite much progress in the control of their magnetic properties, for example through electrostatic gating or control of the stacking order, [6-9] little is known about the mechanisms governing fundamental magnetic processes in the ultrathin limit. For instance, the extensively studied materials CrI 3 (a semiconductor) and Fe 2 GeTe 3 (a metal) are soft ferromagnets in the bulk crystal form with a remanent magnetization far below the saturation magnetization (a few percent), [10,11] but surprisingly, they become hard ferromagnets when exfoliated to a few atomic layers, with a near squareshaped hysteresis and a large coercive field of H c ≈ 0.1−1 T. [1,12-14] Since hard ferromagnetic properties are crucial to applications, especially as a building block for van der Waals magnetic heterostructures, The recent isolation of 2D van der Waals magnetic materials has uncovered rich physics that often differs from the magnetic behavior of their bulk counterparts. However, the microscopic details of fundamental processes such as the initial magnetization or domain reversal, which govern the magnetic hysteresis, remain largely unknown in the ultrathin limit. Here a widefield nitrogen-vacancy (NV) microscope is employed to directly image these processes in few-layer flakes of the magnetic semiconductor vanadium triiodide (VI 3). Complete and abrupt switching of most flakes is observed at fields H c ≈ 0.5-1 T (at 5 K) independent of thickness. The coercive field decreases as the temperature approaches the Curie temperature (T c ≈ 50 K); however, the switching remains abrupt. The initial magnetization process is then imaged, which reveals thickness-dependent domain wall depinning fields well below H c. These results point to ultrathin VI 3 being a nucleation-type hard ferromagnet, where the coercive field is set by the anisotropy-limited domain wall nucleation field. This work illustrates the power of widefield NV microscopy to investigate magnetization processes in van der Waals ferromagnets, which can be used to elucidate the origin of the hard ferromagnetic properties of other materials and explore field-and current-driven domain wall dynamics.

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“…However, the reference DC field can be invasive when measuring the magnetic properties of ferromagnets and superconductors that are sensitive to DC magnetic fields. Therefore, it is desirable to measure the azimuthal angle without a reference DC field for the investigation of various phenomena of magnetic-field-sensitive materials [22,23,36,37].…”

Section: Introductionmentioning

confidence: 99%

Vector DC magnetic-field sensing with reference microwave field using perfectly aligned nitrogen-vacancy centers in diamond

Isogawa¹,

Matsuzaki²,

Ishi‐Hayase³

2021

Preprint

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The measurement of vector magnetic fields with high sensitivity and spatial resolution is important for both fundamental science and engineering applications. In particular, magnetic-field sensing with nitrogen-vacancy (NV) centers in diamond is a promising approach that can outperform existing methods. Recent studies have demonstrated vector DC magnetic-field sensing with perfectly aligned NV centers, which showed a higher readout contrast than NV centers having four equally distributed orientations. However, to estimate the azimuthal angle of the target magnetic field with respect to the NV axis in these previous approaches, it is necessary to apply a strong reference DC magnetic field, which can perturb the system to be measured. This is a crucial problem, especially when attempting to measure vector magnetic fields from materials that are sensitive to applied DC magnetic fields. Here, we propose a method to measure vector DC magnetic fields using perfectly aligned NV centers without reference DC magnetic fields. More specifically, we used the direction of linearly polarized microwave fields to induce Rabi oscillation as a reference and estimated the azimuthal angle of the target fields from the Rabi frequency. We further demonstrate the potential of our method to improve sensitivity by using entangled states to overcome the standard quantum limit. Our method of using a reference microwave field is a novel technique for sensitive vector DC magnetic-field sensing.

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Laser Modulation of Superconductivity in a Cryogenic Wide-field Nitrogen-Vacancy Microscope

Cited by 40 publications

References 49 publications

Magnetic domains and domain wall pinning in atomically thin CrBr3 revealed by nanoscale imaging

Magnetic domains and domain wall pinning in atomically thin CrBr3 revealed by nanoscale imaging

Imaging Domain Reversal in an Ultrathin Van der Waals Ferromagnet

Vector DC magnetic-field sensing with reference microwave field using perfectly aligned nitrogen-vacancy centers in diamond

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