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Cho FH, Park J, Oh S, Yu J, Jeong Y, Colazzo L, Spree L, Hommel C, Ardavan A, Boero G, Donati F. A continuous-wave and pulsed X-band electron spin resonance spectrometer operating in ultra-high vacuum for the study of low dimensional spin ensembles. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2024; 95:063904. [PMID: 38864723 DOI: 10.1063/5.0189974] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2023] [Accepted: 05/09/2024] [Indexed: 06/13/2024]
Abstract
We report the development of a continuous-wave and pulsed X-band electron spin resonance (ESR) spectrometer for the study of spins on ordered surfaces down to cryogenic temperatures. The spectrometer operates in ultra-high vacuum and utilizes a half-wavelength microstrip line resonator realized using epitaxially grown copper films on single crystal Al2O3 substrates. The one-dimensional microstrip line resonator exhibits a quality factor of more than 200 at room temperature, close to the upper limit determined by radiation losses. The surface characterizations of the copper strip of the resonator by atomic force microscopy, low-energy electron diffraction, and scanning tunneling microscopy show that the surface is atomically clean, flat, and single crystalline. Measuring the ESR spectrum at 15 K from a few nm thick molecular film of YPc2, we find a continuous-wave ESR sensitivity of 2.6 × 1011 spins/G · Hz1/2, indicating that a signal-to-noise ratio of 3.9 G · Hz1/2 is expected from a monolayer of YPc2 molecules. Advanced pulsed ESR experimental capabilities, including dynamical decoupling and electron-nuclear double resonance, are demonstrated using free radicals diluted in a glassy matrix.
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Affiliation(s)
- Franklin H Cho
- Center for Quantum Nanoscience, Institute for Basic Science, Seoul 03760, South Korea
- Ewha Womans University, Seoul 03760, South Korea
| | - Juyoung Park
- Center for Quantum Nanoscience, Institute for Basic Science, Seoul 03760, South Korea
- Department of Physics, Ewha Womans University, Seoul 03760, South Korea
| | - Soyoung Oh
- Center for Quantum Nanoscience, Institute for Basic Science, Seoul 03760, South Korea
- Department of Physics, Ewha Womans University, Seoul 03760, South Korea
| | - Jisoo Yu
- Center for Quantum Nanoscience, Institute for Basic Science, Seoul 03760, South Korea
- Department of Physics, Ewha Womans University, Seoul 03760, South Korea
| | - Yejin Jeong
- Center for Quantum Nanoscience, Institute for Basic Science, Seoul 03760, South Korea
- Department of Physics, Ewha Womans University, Seoul 03760, South Korea
| | - Luciano Colazzo
- Center for Quantum Nanoscience, Institute for Basic Science, Seoul 03760, South Korea
- Ewha Womans University, Seoul 03760, South Korea
| | - Lukas Spree
- Center for Quantum Nanoscience, Institute for Basic Science, Seoul 03760, South Korea
- Ewha Womans University, Seoul 03760, South Korea
| | - Caroline Hommel
- Center for Quantum Nanoscience, Institute for Basic Science, Seoul 03760, South Korea
- Ewha Womans University, Seoul 03760, South Korea
| | - Arzhang Ardavan
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, United Kingdom
| | - Giovanni Boero
- Microsystems Laboratory, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne 1015, Switzerland
| | - Fabio Donati
- Center for Quantum Nanoscience, Institute for Basic Science, Seoul 03760, South Korea
- Department of Physics, Ewha Womans University, Seoul 03760, South Korea
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González-Gutiérrez C, García-Pons D, Zueco D, Martínez-Pérez MJ. Scanning Spin Probe Based on Magnonic Vortex Quantum Cavities. ACS NANO 2024; 18:4717-4725. [PMID: 38271997 PMCID: PMC10867890 DOI: 10.1021/acsnano.3c06704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Revised: 01/15/2024] [Accepted: 01/18/2024] [Indexed: 01/27/2024]
Abstract
Performing nanoscale scanning electron paramagnetic resonance (EPR) requires three essential ingredients: First, a static magnetic field together with field gradients to Zeeman split the electronic energy levels with spatial resolution; second, a radio frequency (rf) magnetic field capable of inducing spin transitions; finally, a sensitive detection method to quantify the energy absorbed by spins. This is usually achieved by combining externally applied magnetic fields with inductive coils or cavities, fluorescent defects, or scanning probes. Here, we theoretically propose the realization of an EPR scanning sensor merging all three characteristics into a single device: the vortex core stabilized in ferromagnetic thin-film discs. On one hand, the vortex ground state generates a significant static magnetic field and field gradients. On the other hand, the precessional motion of the vortex core around its equilibrium position produces a circularly polarized oscillating magnetic field, which is enough to produce spin transitions. Finally, the spin-magnon coupling broadens the vortex gyrotropic frequency, suggesting a direct measure of the presence of unpaired electrons. Moreover, the vortex core can be displaced by simply using external magnetic fields of a few mT, enabling EPR scanning microscopy with large spatial resolution. Our numerical simulations show that, by using low damping magnets, it is theoretically possible to detect single spins located on the disc's surface. Vortex nanocavities could also attain strong coupling to individual spin molecular qubits with potential applications to mediate qubit-qubit interactions or to implement qubit readout protocols.
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Affiliation(s)
- Carlos
A. González-Gutiérrez
- Instituto
de Nanociencia y Materiales de Aragón (INMA), CSIC-Universidad de Zaragoza, Zaragoza ES-50009, Spain
- Department
of Physics and Applied Physics, University
of Massachusetts, Lowell, Massachusetts 01854, United States
- Instituto
de Ciencias Físicas, Universidad
Nacional Autónoma de México, Av. Universidad s/n, Cuernavaca, Morelos 62210, México
| | - David García-Pons
- Instituto
de Nanociencia y Materiales de Aragón (INMA), CSIC-Universidad de Zaragoza, Zaragoza ES-50009, Spain
| | - David Zueco
- Instituto
de Nanociencia y Materiales de Aragón (INMA), CSIC-Universidad de Zaragoza, Zaragoza ES-50009, Spain
| | - María José Martínez-Pérez
- Instituto
de Nanociencia y Materiales de Aragón (INMA), CSIC-Universidad de Zaragoza, Zaragoza ES-50009, Spain
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Sojka A, Price BD, Sherwin MS. Order-of-magnitude SNR improvement for high-field EPR spectrometers via 3D printed quasi-optical sample holders. SCIENCE ADVANCES 2023; 9:eadi7412. [PMID: 37729398 PMCID: PMC10511183 DOI: 10.1126/sciadv.adi7412] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Accepted: 08/18/2023] [Indexed: 09/22/2023]
Abstract
Here, we present a rapidly prototyped, cost-efficient, and 3D printed quasi-optical sample holder for improving the signal-to-noise ratio (SNR) in modern, resonator-free, and high-field electron paramagnetic resonance (HFEPR) spectrometers. Such spectrometers typically operate in induction mode: The detected EPR ("cross-polar") signal is polarized orthogonal to the incident ("co-polar") radiation. The sample holder makes use of an adjustable sample positioner that allows for optimizing the sample position to maximize the 240-gigahertz magnetic field B1 and a rooftop mirror that allows for small rotations of the microwave polarization to maximize the cross-polar signal and minimize the co-polar background. When optimally tuned, the sample holder was able to improve co-polar isolation by ≳20 decibels, which is proven beneficial for maximizing the SNR in rapid-scan, pulsed, and continuous-wave EPR experiments. In rapid-scan mode, the improved SNR enabled the recording of entire EPR spectra of a narrow-line radical in millisecond time scales, which, in turn, enabled real-time monitoring of a sample's evolving line shape.
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Affiliation(s)
- Antonín Sojka
- Department of Physics, University of California, Santa Barbara, Santa Barbara, CA, USA
- Institute for Terahertz Science and Technology, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Brad D. Price
- Department of Physics, University of California, Santa Barbara, Santa Barbara, CA, USA
- Institute for Terahertz Science and Technology, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Mark S. Sherwin
- Department of Physics, University of California, Santa Barbara, Santa Barbara, CA, USA
- Institute for Terahertz Science and Technology, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
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Wiedemann HTA, Ruloff S, Richter R, Zollitsch CW, Kay CWM. Towards high performance dielectric microwave resonators for X-band EPR spectroscopy. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2023; 354:107519. [PMID: 37541024 DOI: 10.1016/j.jmr.2023.107519] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 06/27/2023] [Accepted: 06/28/2023] [Indexed: 08/06/2023]
Abstract
Microwave (MW) resonators in Electron Paramagnetic Resonance (EPR) spectroscopy concentrate the MW magnetic field (B1) at the sample and separate the MW electric field from the sample. There are numerous experimental methods in EPR spectroscopy which all impose different requirements on MW resonators (e.g. high or low quality factor, MW conversion, and B1-field homogeneity). Although commercial spectrometers offer standardized MW resonators for a broad application range, newly emerging and highly-specialized research fields push these spectrometers to or beyond their sensitivity limits. Optimizing the MW resonator offers one direct approach to improve the sensitivity. Here we present three low-cost optimization approaches for a commercially available X-band (9-10 GHz) MW resonator for three experimental purposes (continuous-wave (CW), transient and pulse EPR). We obtain enhanced MW conversion factors for all three optimized resonators and higher quality factors for two optimized resonators. The latter is important for CW and transient EPR. Furthermore, we fabricated a resonator which features an extended area of homogeneous B1-field and, hence, improved pulse EPR performance. Our results demonstrate that small changes to a commercial MW resonator can enhance its performance in general or for specific applications.
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Affiliation(s)
- Haakon T A Wiedemann
- Department of Chemistry, Saarland University, Saarbrücken 66123, Saarland, Germany.
| | - Stefan Ruloff
- Department of Chemistry, Saarland University, Saarbrücken 66123, Saarland, Germany
| | - Rudolf Richter
- Department of Chemistry, Saarland University, Saarbrücken 66123, Saarland, Germany
| | - Christoph W Zollitsch
- Department of Chemistry, Saarland University, Saarbrücken 66123, Saarland, Germany; London Centre of Nanotechnology, University College London, London WC1H 0AH, United Kingdom; Department of Physics & Astronomy, University College London, London WC1E 6BT, United Kingdom
| | - Christopher W M Kay
- Department of Chemistry, Saarland University, Saarbrücken 66123, Saarland, Germany; London Centre of Nanotechnology, University College London, London WC1H 0AH, United Kingdom
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Lapa PN, Kassabian G, Basaran AC, Schuller IK. Detection of electromagnetic phase transitions using a helical cavity susceptometer. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2023; 94:064710. [PMID: 37862535 DOI: 10.1063/5.0136523] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2022] [Accepted: 06/05/2023] [Indexed: 10/22/2023]
Abstract
Fast and sensitive phase transition detection is one of the most important requirements for new material synthesis and characterization. For solid-state samples, microwave absorption techniques can be employed for detecting phase transitions because it simultaneously monitors changes in electronic and magnetic properties. However, microwave absorption techniques require expensive high-frequency microwave equipment and bulky hollow cavities. Due to size limitations in conventional instruments, it is challenging to implement these cavities inside a laboratory cryostat. In this work, we designed and built a susceptometer that consists of a small helical cavity embedded into a custom insert of a commercial cryostat. This cavity resonator operated at sub-GHz frequencies is extremely sensitive to changes in material parameters, such as electrical conductivity, magnetization, and electric and magnetic susceptibilities. To demonstrate its operation, we detected superconducting phase transition in Nb and YBa2Cu3O7-δ, metal-insulator transitions in V2O3, ferromagnetic transition in Gd, and magnetic field induced transformation in meta magnetic NiCoMnIn single crystals. This high sensitivity apparatus allows the detection of trace amounts of materials (10-9-cc) undergoing an electromagnetic transition in a very broad temperature (2-400 K) and magnetic field (up to 90 kOe) ranges.
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Affiliation(s)
- Pavel N Lapa
- Department of Physics and Center for Advanced Nanoscience, University of California San Diego, La Jolla, California 92093, USA
| | - George Kassabian
- Department of Physics and Center for Advanced Nanoscience, University of California San Diego, La Jolla, California 92093, USA
| | - Ali C Basaran
- Department of Physics and Center for Advanced Nanoscience, University of California San Diego, La Jolla, California 92093, USA
| | - Ivan K Schuller
- Department of Physics and Center for Advanced Nanoscience, University of California San Diego, La Jolla, California 92093, USA
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