Microwave losses in incipient ferroelectrics as functions of the temperature and the biasing field

Vendik, O. G.; Ter-Martirosyan, L. T.; Zubko, S. P.

doi:10.1063/1.368166

Cited by 111 publications

(66 citation statements)

References 17 publications

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“…The KTaO 3 insert was assumed to have a relative dielectric constant r = 261 and loss tangent tan ␦ = 7.5ϫ 10 −4 at room temperature. 3,16,17 The dielectric length was varied over the range 1 mmϽ l d Ͻ 3 mm, giving an isolated natural resonance frequency of 9.4947 GHz at 1.75 mm. At this diameter, the isolated dielectric resonator efficiency parameter ⌳ d = 41.01 G / W 1/2 .…”

Section: Resultsmentioning

confidence: 99%

Dielectric microwave resonators in TE011 cavities for electron paramagnetic resonance spectroscopy

Mett

Sidabras

Головина

et al. 2008

Review of Scientific Instruments

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The coupled system of the microwave cylindrical TE 011 cavity and the TE 01␦ dielectric modes has been analyzed in order to determine the maximum achievable resonator efficiency parameter of a dielectric inserted into a cavity, and whether this value can exceed that of a dedicated TE 01␦ mode dielectric resonator. The frequency, Q value, and resonator efficiency parameter ⌳ for each mode of the coupled system were calculated as the size of the dielectric was varied. Other output parameters include the relative field magnitudes and phases. Two modes are found: one with fields in the dielectric parallel to the fields in the cavity center and the other with antiparallel fields. Results closely match those from a computer program that solves Maxwell's equations by finite element methods. Depending on the relative natural resonance frequencies of the cavity and dielectric, one mode has a higher Q value and correspondingly lower ⌳ than the other. The mode with the higher Q value is preferentially excited by a coupling iris or loop in or near the cavity wall. However, depending on the frequency separation between modes, either can be excited in this way. A relatively narrow optimum is found for the size of the insert that produces maximum signal for both modes simultaneously. It occurs when the self-resonance frequencies of the two resonators are nearly equal. The maximum signal is almost the same as that of the dedicated TE 01␦ mode dielectric resonator alone, ⌳ Х 40 G / W 1/2 at X-band for a KTaO 3 crystal. The cavity is analogous to the second stage of a two-stage coupler. In general, there is no electron paramagnetic resonance ͑EPR͒ signal benefit by use of a second stage. However, there is a benefit of convenience. A properly designed sample-mounted resonator inserted into a cavity can give EPR signals as large as what one would expect from the dielectric resonator alone.

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Section: Resultsmentioning

confidence: 99%

Dielectric microwave resonators in TE011 cavities for electron paramagnetic resonance spectroscopy

Mett

Sidabras

Головина

et al. 2008

Review of Scientific Instruments

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“…Similarly, studies of microwave dissipation and relaxation in magnetic or dielectric materials have received great attention recently, e.g., to resolve the coupling of spins and charges in magnetic superconductors like the borocarbides or rutheno-cuprates [6,7,8], or materials displaying colossal magneto-resistance [9], or to search for low-loss ferrite or ferroelectric materials for frequency-agile devices [10,11,12]. …”

Section: Theoretical Backgroundmentioning

confidence: 99%

Recent developments in the characterization of superconducting films by microwaves

Hein

Getta

Kreiskott

et al. 2002

Physica C: Superconductivity

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We describe and analyze selected surface impedance data recently obtained by different groups on cuprate, ruthenate and diboride superconducting films on metallic and dielectric substrates for fundamental studies and microwave applications. The discussion includes a first review of microwave data on MgB 2 , the weak-link behaviour of RABiTS-type YBa 2 Cu 3 O 7-δ tapes, and the observation of a strong anomalous powerdependence of the microwave losses in MgO at low temperatures. We demonstrate how microwave measurements can be used to investigate electronic, magnetic, and dielectric dissipation and relaxation in the films and substrates. The impact of such studies reaches from the extraction of microscopic information to the engineering of materials and further on to applications in power systems and communication technology.Keywords: Surface impedance, superconducting films, microwave dissipation, relaxation.Address: Dr. Matthias Hein, Dept. of Physics, Univ. of Wuppertal, D-42097 Wuppertal, Germany. Tel. +49(202) 439-2747, Fax +49(202) Email: mhein@venus.physik.uni-wuppertal.de M. Hein et al., EUCAS 2001, invited paper B3-01, page 2 of 19 Microwave measurements in condensed matter physics Theoretical backgroundThis paper illustrates the relevance of microwave measurements for the investigation of electronic and magnetic transport and ordering in condensed matter. While most work has been done on solids, the described techniques could also be adapted to soft matter or liquids.The presentation is based on a selection of examples and does not attempt to provide a complete description of activities in this field.The complex-valued surface impedance Z s =R s +iX s at a microwave frequency ω=2πf is related to the permeability and conductivity of a material, µ and σ, in the local limit by ) (where R s and X s are the surface resistance and reactance [1]. The material parameters µ and σ are complex-valued and frequency dependent, e.g., via electronic, magnetic, or dielectric relaxation. The generalized conductivity σ characterizes electrical conduction through transport and displacement currents.The electrodynamic response of metallic materials provides information on the electronic properties within a surface layer of the order of the London penetration depth ~200 nm, and on a variable time scale ∼1/ω. Such information is complementary to thermodynamic bulk properties and low-frequency transport data. The high frequencies also help to derive Fermi surface properties, which would require strong magnetic fields at very low temperatures otherwise [2]. We will focus in the following on superconductors, for which Z s bears information on the density of states and quasiparticle excitations above and below the transition temperature T c [3]. It is also related to the phase purity, grain connectivity and interface effects of technical materials, which cannot readily be studied at similar resolution by At present at least 50 renowned academic and industrial groups study superconductors at microwave frequencies, to ...

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“…Identification of the dominant loss mechanisms in thin films at microwave frequencies is often complicated due to contributions from electrodes, which may dominate the loss characteristics of devices at high frequencies [5,6]. Recently, several authors have proposed to use the bias field dependence of the dielectric loss as a method to distinguish between different loss mechanisms [7,8].…”

Section: Introductionmentioning

confidence: 99%

Contributions to the dielectric losses of textured SrTiO3 thin films with Pt electrodes

Schmidt

et al. 2005

Journal of Applied Physics

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The factors controlling low frequency (1 MHz) dielectric losses of textured SrTiO 3 thin films deposited by radio-frequency magnetron sputtering on platinized sapphire substrates were investigated. In particular, the influence of film texture, phase transformations, applied bias field, temperature and annealing atmospheres was studied. Films that were (111) textured showed a phase transformation at ~ 150 K, whereas films that were predominantly (110) oriented did not exhibit a phase transformation in the measured temperature range (100 K -300 K). Two major contributions to the dielectric losses were identified: a low temperature loss increase for the (111) oriented film, which could be suppressed by an applied bias field, and a loss peak at 2 50 K (at 1 MHz), which was strongly frequency dependent and likely associated with a relaxing defect. The low temperature loss mode was related to the appearance of a phase transformation and contributed to the dielectric losses even at temperatures that were more than 100 K above the phase transformation. In contrast to the leakage properties of the films, which were strongly dependent on annealing atmospheres, annealing under reducing conditions had no significant influence on any of the observed loss modes. Possible origins of the different loss contributions are discussed.3

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Microwave losses in incipient ferroelectrics as functions of the temperature and the biasing field

Cited by 111 publications

References 17 publications

Dielectric microwave resonators in TE011 cavities for electron paramagnetic resonance spectroscopy

Dielectric microwave resonators in TE011 cavities for electron paramagnetic resonance spectroscopy

Recent developments in the characterization of superconducting films by microwaves

Contributions to the dielectric losses of textured SrTiO3 thin films with Pt electrodes

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