Scaling of sensitivity and efficiency in planar microresonators for electron spin resonance

Narkowicz, R.; Suter, Dieter; Niemeyer, I.

doi:10.1063/1.2964926

Cited by 85 publications

(58 citation statements)

References 22 publications

(20 reference statements)

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“…Until now the main strategy to overcome such problems was to measure the response of the system at a few discrete and widely-spaced frequencies [2]. Another approach is to reduce the dimension of the ESR cavities to micrometer size while at the same time somewhat relaxing the resonance requirements [3][4][5]. In this way small sample quantities can be probed over a wider frequency range.…”

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confidence: 99%

Broadband electron spin resonance from 500 MHz to 40 GHz using superconducting coplanar waveguides

Clauss

Bothner

Koelle

et al. 2013

Applied Physics Letters

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We present non-conventional electron spin resonance (ESR) experiments based on microfabricated superconducting Nb thin film waveguides. A very broad frequency range, from 0.5 to 40 GHz, becomes accessible at low temperatures down to 1.6 K and in magnetic fields up to 1.4 T. This allows for an accurate inspection of the ESR absorption position in the frequency domain, in contrast to the more common observation as a function of magnetic field. We demonstrate the applicability of frequency-swept ESR on Cr 3+ atoms in ruby as well as on organic radicals of the Nitronylnitroxide family. Measurements between 1.6 and 30 K reveal a small frequency shift of the ESR and a resonance broadening below the critical temperature of Nb, which we both attribute to a modification of the magnetic field configuration due to the appearance of shielding supercurrents in the waveguide.PACS numbers: 87.80. Lg, 76.30.Rn, 84.40.Az, 07.57.Pt To improve the performance of electron spin resonance (ESR) systems the main strategy was the use resonant of cavities with higher and higher fields and frequencies. As a result, most modern instrumentation can operate only at a single frequency or in an extremely narrow frequency range [1]. However, this can be a serious hindrance when a frequency-dependent effect is to be observed, as needed to probe a complete phase diagram of some material or to reliably assess the distance and orientation of spin labels. The latter problem, in particular, is increasingly important in the domain of biological ESR, as it is fundamental to understand the structural conformation and dynamics of biological systems. Until now the main strategy to overcome such problems was to measure the response of the system at a few discrete and widely-spaced frequencies [2]. Another approach is to reduce the dimension of the ESR cavities to micrometer size while at the same time somewhat relaxing the resonance requirements [3][4][5]. In this way small sample quantities can be probed over a wider frequency range. Setups that offer the possibility to sweep both the magnetic field and the radiation frequency have so far mostly been realized in the high frequency region (quasi-optical, from 50 to several 100 GHz) [6][7][8], while lower frequencies have been inspected using a coupled antenna approach [9], tuneable cavities [10] or by placing the sample close to the center conductor of a coaxial line [11].In this letter we demonstrate a different approach which uses a microfabricated superconducting coplanar waveguide to generate the radio frequency (RF) field. The feasibility of such an approach was shown before by Schuster et al. focusing on high-cooperativity coupling of spin ensembles to superconducting cavities [12]. Similar devices are also used to study ferromagnetic resonances of various materials [13][14][15][16]. Using superconducting waveguides one can obtain higher RF fields (with same input power) and no ohmic heating of the sample, as will be shown later. We show that it is possible to probe both the frequency and field d...

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confidence: 99%

Broadband electron spin resonance from 500 MHz to 40 GHz using superconducting coplanar waveguides

Clauss

Bothner

Koelle

et al. 2013

Applied Physics Letters

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“…The observation can be explained by the magnetoresistance of copper at higher fields [35]. Planar structures (microstrip, stripline and coplanar) have already been employed for ESR experiments [15,[36][37][38][39][40][41][42][43][44][45][46]. Although microstrip and stripline resonators have also been successfully applied in ESR measurements [36-38, 41, 45, 47], coplanar configurations might be more appropriate candidates since they carry the signal non-dispersively in contrast to a microstrip configuration [45,48].…”

Section: Resultsmentioning

confidence: 99%

Metallic coplanar resonators optimized for low-temperature measurements

Rahim¹,

Lehleiter²,

Bothner³

et al. 2016

J. Phys. D: Appl. Phys.

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Metallic coplanar microwave resonators are widely employed at room temperature, but their low-temperature performance has received little attention so far. We characterize compact copper coplanar resonators with multiple modes from 2.5 to 20 GHz at temperatures as low as 5 K. We investigate the influence of center conductor width (20 to 100 µm) and coupling gap size (10 to 50 µm), and we observe a strong increase of quality factor (Q) for wider center conductors, reaching values up to 470. The magnetic-field dependence of the resonators is weak, with a maximum change in Q of 3.5% for an applied field of 7 T. This makes these metallic resonators well suitable for magnetic resonance studies, as we document with electron spin resonance (ESR) measurements at multiple resonance frequencies.

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“…In this technique, the VNA acts as both source and detector, in which the two-port VNA device is connected, via high-frequency cables, to a coplanar waveguide system consisting typically of a coplanar waveguide (CW) or stripline. The use of a planar microresonator (PMR) can also increase sensitivity of the measurement [241], though limits measurement to a fixed frequency, as we will discuss shortly. For the coplanar stripline, there is no resonant cavity, which means that measurements can be made over a broad range of frequencies (commonly referred to as a broadband FMR measurement).…”

Section: Ferromagnetic Resonancementioning

confidence: 99%