Dielectric properties of rutile and its use in high temperature superconducting resonators

Abstract

The microwave properties of single crystalline TiO2 (rutile) were investigated. At a frequency of 7.5 GHz the loss tangent tan δ was found to increase from 1.4×10−7 at 4 K to 4×10−6 at 70 K for electric fields parallel to the crystallographic a,b plane. The high permittivity of 105 and the small tanδ in combination with the low microwave losses of high temperature superconductors (HTS) were utilized to construct a miniaturized X-band resonator with a high quality factor Q. An assembly of two YBa2Cu3O7 films of 8 mm in diameter separated by a rutile cylinder of 2 mm height provides a TE011 resonance at 9.7 GHz with Qs ranging from 6×105 at 10 K to 105 at 70 K. Frequency scaling of the losses in rutile and in the HTS films indicates Qs in excess of 106 at 1.8 GHz using YBa2Cu3O7 films of two inches in diameter. Such resonators are considered to be key elements for high-power filters in mobile communications.

Microwave properties of MgB/sub 2/ thin films

“…Indeed, MgB seems to comprise values of the order or less than this error margin, because (4.2 K) for a MgB was found almost to be the same as with niobium film. In order to improve the measurement resolution a rutile puck has been used to measure because of its higher dielectric constant [27], [28]. In this case the field energy concentration inside the puck works more effectively and the maximum with a niobium reference sample is about a factor of ten higher.…”

Vortex motion in Nb/PdNi/Nb trilayers: New aspects in the flux flow state

“…The dielectric rod is placed onto the sample, which in turn is partially masked by a thin metal mask with a circular hole in order to maintain the azimuthal symmetry, and it is in close contact with the bottom wall of the enclosure. The high permittivity of rutile ( r ∼100, for a detailed characterization see [11]) ensures that the evanescent electromagnetic field drops quickly to zero out of the dielectric. The DR works in transmission with very weak coupling, thus making corrections of the directly measured quality factor Q unnecessary [12].…”

Comparison between nonlinear measurements in patterned and unpatterned thin films

“…The term T α,2ω1−ω2 is equal to 0.3617 for α = 1.2 and 0.0252 for α = 0.1, being j 1 /j 2 = 1 since the two input tones have the same power [3]. With all of these parameters, the nonlinear term | R α + j ω 0 L α | has to be 2.21 × 10 −6 m α /A α for region 1 and 0.001 m α /A α for region 2, according to (4).…”

“…As an example of the procedure, we have characterized the nonlinearities in a 10 × 10 mm 2 YBCO thin film on MgO, by measuring the intermodulation products with a rutile-loaded cavity operating at TE 011 mode [4] and a coplanar half-wave resonator.…”