Abstract

The physical nature and concentration of paramagnetic point defects in the dielectrics of superconducting planar microwave resonators have been determined using in-situ electron paramagnetic resonance spectroscopy. To perform this work, the quality factor of parallel plate and stripline resonators was measured as a function of the magnitude of a magnetic-field applied parallel to the electrode surfaces. YBa2Cu3O7-δ thin film electrodes proved to be a preferred choice over Nb and MgB2 because they are readily available and have a small surface resistance (Rs) up to high temperatures (∼77 K) and magnetic fields (i.e., <1 T). Stripline resonators with a widely used high performance microwave dielectric, Co2+-doped Ba(Zn1/3Nb2/3)O3, are shown to have losses dominated by d-electron spin-excitations in exchange-coupled Co2+ point-defect clusters, even in the absence of an applied magnetic field. A significant enhanced microwave loss in stripline and parallel plate resonators is found to correlate with the presence of paramagnetic Mn2+ dopants in Ba(Zn1/3Ta2/3)O3 ceramics and dangling bond states in amorphous Si thin films, although the identification of the dominant loss mechanism(s) in these dielectrics requires further investigation.

Original languageEnglish (US)
Article number122602
JournalApplied Physics Letters
Volume109
Issue number12
DOIs
StatePublished - Sep 19 2016

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point defects
electron paramagnetic resonance
resonators
microwaves
parallel plates
magnetic fields
electrodes
thin films
electron spin
Q factors
ceramics
spectroscopy
excitation

ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)

Cite this

In-situ electron paramagnetic resonance studies of paramagnetic point defects in superconducting microwave resonators. / Zhang, Shengke; Kopas, Cameron; Wagner, Brian; Queen, Daniel; Newman, Nathan.

In: Applied Physics Letters, Vol. 109, No. 12, 122602, 19.09.2016.

Research output: Contribution to journalArticle

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