Debye relaxation in high magnetic fields

Abstract

Dielectric relaxation is universal in characterizing polar liquids and solids, insulators, and semiconductors, and the theoretical models are well developed. However, in high magnetic fields, previously unknown aspects of dielectric relaxation can be revealed and exploited. Here, we report low temperature dielectric relaxation measurements in lightly doped silicon in high dc magnetic fields B both parallel and perpendicular to the applied ac electric field E. For B//E, we observe a temperature and magnetic field dependent dielectric dispersion ε(ω) characteristic of conventional Debye relaxation where the free carrier concentration is dependent on thermal dopant ionization, magnetic freeze-out, and/or magnetic localization effects. However, for B⊥E, anomalous dispersion emerges in ε(ω) with increasing magnetic field. It is shown that the Debye formalism can be simply extended by adding the Lorentz force to describe the general response of a dielectric in crossed magnetic and electric fields. Moreover, we predict and observe a new transverse dielectric response E H ⊥ B ⊥ E not previously described in magnetodielectric measurements. The new formalism allows the determination of the mobility and the ability to discriminate between magnetic localization/freeze out and Lorentz force effects in the magneto-dielectric response.

Magnetocapacitance without magnetism

“…Furthermore, our results are possibly relevant to rough interfaces in heterostructures [26]. Experiments on nanoporous silicon [10,11] have revealed a magnetic-field-dependent dielectric resonance that is consistent with our model. In this case, the dielectric response was measured at fixed frequency ω = 100 kHz as a function of temperature T = 25-40 K and magnetic field H = 0-32 T. However, varying the temperature is equivalent to varying ωτ if we approximate ε as temperature independent and the electrical transport in the semiconductor as being activated: ρ = ρ 0 e /k B T , where is the activation gap.…”

“…In particular, we see that the dependence on p is inverted for low and high frequencies, because the dielectric regions effectively behave insulating in the former Figure 6. Position of the resonance peak in the imaginary part of the dielectric response in terms of inverse temperature 1/T as a function of magnetic field H. Triangles are data for nanoporous silicon taken from Brooks et al [11], whereas the line corresponds to a fit from our classical model of conductor-dielectric composites. (Online version in colour.…”

Dielectric properties of single crystal spinels in the series FeV2O4, MnV2OKismarahardja1, Brooks2, Zhou3 et al. 2013Phys. Rev. BSelf Cite

“…These parameters are not strongly fielddependent. Provided a glassy state describes the behavior, we estimate that the corresponding glass transition to be about T g ~ 10 K. In contrast to the other two spinels studied, CoV 2 O 4 exhibits a slight frequency dependence of the temperature dependent dielectric response [17] characteristic of electric dipole (Debye) relaxation [25]. Arrhenius analysis indicates a dipole oscillator with a characteristic energy of about 20 meV.…”

Magnetoresistive polyaniline–silicon carbide metacomposites: plasma frequency determination and high magnetic field sensitivity

“…52 In order to fit the optical data on the metals in these regions, the Debye relaxation time  (which describes the response of electric dipoles to an alternating electric field and the essential dynamics are expressed by the exponential relation (i/) of the dipole polarization with time. 53 ) is introduced to modify the Drude model to interpret the frequency dependent permittivity property as Equation (2): 52, 54…”