Field-induced Frequency Shifts Research Articles

Magnetic field tunable piezoelectric resonator for MEMS applications

In this report, the Ni0.50Mn0.35In0.15/Pb0.96La0.04Zr0.52Ti0.48O3 (Ni-Mn-In/PLZT) bulk acoustic wave (BAW) resonator has been fabricated using the sputtering deposition technique. The magnetoelectric effect in the Ni-Mn-In/PLZT resonator has been investigated. The increase in magnetoelectric coupling coefficient (MECC) with the increment in the frequency of applied HAC is observed. The potential of the Ni-Mn-In/PLZT BAW resonator as a magnetic sensor is tested by measuring the shift in the resonant frequency of the reflective (S11 parameter) response in the presence of the externally applied magnetic field. The Ni-Mn-In/PLZT resonator exhibits a frequency shift of 730 MHz in the 1200 Oe magnetic field, among the largest magnetic field-induced frequency shifts in literature. The rarely reported complete dependence of acoustic velocity, coupling coefficients, magnetic sensitivity, and frequency peak shift on the strength of the external magnetic field is investigated. The acoustic velocity increases from 1237 m/s to 1394 m/s, and the electromechanical coupling coefficient increases from 0.0199 % to 0.0206 % after applying the 1200 Oe magnetic field. The reflective responses have been fitted using the Modified-Butterworth Van Dyke (MBVD) model in terms of hardly reported RLC equivalent circuits. The experimental results and extracted parameters from MBVD modeling exhibit high accuracy. This interaction between multiferroic orders and elastic resonance peaks opens a new window for highly sensitive future magnetic field sensors, wireless communication devices, and magnetic field tunable filters.

Large non-saturating shift of the torsional resonance in a doubly clamped magnetoelastic resonator

The magnetic field dependence of the resonance frequencies of Co1−xFex thin film microfabricated resonators was examined for fields applied in the plane of the film. Remarkably, the observed resonance frequency shift with an applied magnetic field did not saturate even up to fields of nearly 2 T. A minimized mechanical and magnetic free energy model of clamped–clamped resonators revealed that for a two-dimensional structure, both bending and torsional modes are allowed, but would have have very different resonance shift behavior with the applied field. A post-anneal of the structure confirms this case by increasing the stress-induced anisotropy of CoFe, which selectively enhances the contribution of the torsional mode and creates the non-saturating field-induced frequency shift. By using the resonance shift in this device in a potential magnetic field sensing paradigm, such a non-saturating torsional mode may be useful for applications such as nuclear magnetic resonance or MRI, which specifically requires sensitive detection of small fluctuations in high magnetic fields.

Magnetic field tuning of spin resonance in TmFeO3 single crystal probed with THz transient

TmFeO3, a canted antiferromagnet, has two intrinsic spin resonance modes in the terahertz (THz) frequency regime: quasi-ferromagnetic (q-FM) mode and quasi-antiferromagnetic (q-AFM) mode. Both the q-FM and q-AFM modes show strong magnetic field and temperature dependence. Hereby, by employing THz time-domain spectroscopy combined with external magnetic field and low temperature system, we systematically investigated the magnetic field induced frequency shift of q-FM and q-AFM modes as well as the temperature driven spin reorientation phase transition in TmFeO3 single crystal. In contrast to the isotropic temperature dependent two-mode, the magnetic field dependence of two-mode is strongly anisotropic: the magnetic field applied along c-axis (a-axis) can harden (soften) the spin resonance frequency of q-FM mode for Γ4 phase of TmFeO3, and the field applied along b-axis shows negligible frequency shift for the q-FM mode, with the q-AFM mode relatively stable. The present study provides solid evidence that the magnetic anisotropy in rare earth orthoferrite plays a dominant role in the q-FM mode and the occurrence of spin reorientation phase transition. With the magnetic anisotropic energy obtained from the temperature dependent q-FM and q-AFM mode frequencies, we can predict both magnetic field and temperature dependence of spin resonance in TmFeO3 single crystal via phenomenological analysis.

Thickness-shear vibration of a quartz plate connected to piezoelectric plates and electric field sensing

We study thickness-shear vibration of a quartz plate connected to two piezoelectric ceramic plates with initial deformations caused by a biasing electric field. The theory for small deformations superposed on finite biasing deformations in an electroelastic body is used. It is shown that the resonant frequencies of the incremental thickness-shear vibration of the quartz plate vary with the biasing electric field. The biasing electric field induced frequency shift depends linearly on the field. Therefore this effect may be used for electric field sensing. The dependence of the electric field induced frequency shift on various material and geometric parameters is examined. When the electric field is of the order of 100 V/mm, the relative frequency shift is of the order of 10 −5. The case when the piezoelectric plates are replaced by piezomagnetic plates is also investigated for magnetic field sensing, and similar results are obtained.

Compensation of field-induced frequency shifts in Ramsey spectroscopy of optical clock transitions

We have extended Ramsey spectroscopy by stepping the probe frequency during the two Ramsey excitation pulses to compensate frequency shifts induced by the excitation itself. This makes precision Ramsey spectroscopy applicable even for transitions that have Stark and Zeeman shifts comparable to the spectroscopic resolution. The method enables a new way to evaluate and compensate key frequency shifts, which benefits in particular, optical clocks based on magnetic field-induced, spectroscopy, two-photon transitions, or heavily forbidden transitions.

Phonon structure inSrTiO3under finite electric fields: First-principles density functional approach

A first-principles approach within the density-functional theory is proposed to determine the phonon structure of infinite solids under finite electric fields. The approach is applied to perovskite $\mathrm{Sr}\mathrm{Ti}{\mathrm{O}}_{3}$, confirming the existence of giant field-induced frequency shifts. Our theory further predicts a striking piezoelectric response as well as a wide-range dielectric tunability. A microscopic understanding for individual phonon modes under finite electric fields is also provided.

Precise measurement of density-dependent shift by wavelength modulation reflection spectroscopy

The density dependence of the line shift of the cesium D2 line is studied with sub-Doppler selective reflection spectroscopy. By use of wavelength modulation and sixth-harmonics detection we observed the coefficient of the pressure-induced shift of the 6S1/2(F=4) →6P3/2(F'=3) hyperfine transition of the cesium D2 line Δδ/ρ = -0.9(5)×10-8cm3. In the limit ρ=0 a frequency shift about -3MHz remains, which may be attributed to long-range atom-surface interactions. The experimental results can be used in measurements of the local field-induced frequency shift at high atomic densities with sufficient accuracy.

Electric field dependence of pocket and nonpocket impurity gap modes in KI and the establishment of Ag+ quadrupolar deformability.

Far-infrared static electric field measurements have been made for a variety of KI point defects which produce vibrational modes in the pure crystal phonon gap. The extremely small field-induced frequency shifts (\ensuremath{\le}0.02 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$) of the KI gap modes associated with anion impurities were accurately determined with a precision of \ifmmode\pm\else\textpm\fi{}0.003 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ by using a global analysis method. No frequency shifts were observed for the ${\mathrm{Rb}}^{+}$ or ${\mathrm{Cs}}^{+}$ gap modes, up to the maximum applied field of \ensuremath{\sim}100 kV/cm in the [100] direction. Most revealing are the field-induced frequency shifts for the pocket gap modes associated with the ${\mathrm{Ag}}^{+}$ impurity, which are nearly two orders of magnitude smaller than the field-induced shifts measured for low-frequency ${\mathrm{Ag}}^{+}$-induced resonant modes. The fact that the pocket-mode displacements are sharply peaked on the (200) family of ions renders them sensitive to the host-lattice anharmonicity near those sites, whereas the resonant modes probe the defect and its nearest neighbors. These E-field measurements and earlier stress-shift measurements are analyzed using a quasiharmonic perturbed shell model. In this approach the effect of either an applied stress or an applied E field is to move the equilibrium positions of the ions, thereby renormalizing the harmonic force constants via the local cubic and quartic anharmonicity.The two types of experiments produce local strains of orthogonal symmetries, and hence provide complementary information. The theoretical analysis of the E field and stress measurements allows us to establish firmly that the ${\mathrm{Ag}}^{+}$ ion in KI possesses a significant electronic quadrupolar deformability. In turn, this finding strongly supports earlier suggestions that the silver ion quadrupolar deformability is an important feature in the dynamics of other host-silver defect systems and of the silver halides. \textcopyright{} 1996 The American Physical Society.

Optical, nonlinear optical, and electrooptical properties of 4'-nitrobenzylidene-3-acetamino-4-methoxyaniline (MNBA) crystals

Optical, nonlinear optical, and electrooptical pg-properties of 4'-nitrobenzylidene-3-acetamino-4-methoxyaniline (MNBA) single crystals have been investigated. The refractive indices were determined in the wavelength range of 514 to 1064 nm using an interferometric method. The electrooptical coefficients r/sub 11/, r/sub 13/, r/sub 31/, and r/sub 33/ were measured using a phase modulation technique. The dispersion of the largest electrooptical coefficient, r/sub 11/ (=29 pm/V at /spl lambda/=633 nm), was seen to follow the theoretical two-level model. Using the standard Maker fringe technique, we determined the nonlinear optical susceptibilities. The largest coefficient was found to be d/sub 11/=175 pm/V at /spl lambda/=1064 nm. Electric-field-induced second-harmonic generation was used for the determination of the molecular second-order nonlinear optical susceptibility yielding a good quantitative agreement when compared with the largest nonlinear optical and electrooptical coefficients in the framework of the molecular gas model with charge transfer along the polar molecular axis. Electroabsorption measurements near the band edge were performed that allowed us to calculate the field-induced frequency shift of the dominant oscillator. This field-induced frequency shift is of the same order of magnitude as the frequency shift calculated from the electric field-induced changes of the refractive indices (electrooptical effect).< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Measurement of cesium resonance line self-broadening and shift with doppler-free selective reflection spectroscopy

The density dependence of the line width and resonance frequency of the cesium D 1 line is studied with Doppler-free frequency modulated selective reflection spectroscopy. The experimental coefficient of self-broadening γ col / N = 2 Π × 7.5 (1.1) × 10 -8 cm 3 Hz is in good agreement with theoretical predictions. Also is observed a density-dependent shift with the coefficient Δv col / N = -0.9 (5) × 10 -8 cm 3 Hz. In the limit N = 0 a frequency shift of -3.0(4) MHz remains that may be attributed to long-range atom- surface interactions. The experimental results can be used in measurements of the local field-induced frequency shift at high atomic densities.

Electroelastic Effect in Tourmaline

Measuring the electric field induced frequency shift of tourmaline resonators the electroelastic constants g311 and δ333 are determined. These constants may be interpreted as describing either the electric field dependence of an elastic constant or the stress (strain) dependence of a piezoelectric constant, Fields u p to about 3 x 106 V/m were used. Within this range the effect is linear and is of the same order as in α-quartz