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A consistent study of the consequence of the azimuthal angle φ on the susceptibility and the hysteresis of the nanoparticles is performed, we treat the problem with Brown’s magnetic equation thereby extending the statistical moment method. The (DMH) loops are obtained, the principal-axis of the magnetization is oriented to the direction of the field under an any azimuthal angle. It’s demonstrated that the hysteresis and the nonlinear ac susceptibility powerfully depend on the Azimuthal angle φ.

The magnetostrictive delay line (MDL) principle is used to evaluate the magnetic and magnetostrictive properties of materials with waveguide-like shape, such as ribbons and wires. The material under test is used as the MDL on which a pulsed field along with a dc bias field is applied at the excitation point while another dc bias field is applied at the receiving end. Theoretical analysis shows that varying the dc bias field at the receiving end while keeping the excitation field constant results in the dc differential permeability measurement, the integral of which yields the dc hysteresis loop of the material, i.e., $\mbi{B(H)}$ . The response obtained upon varying the dc bias field at the excitation point, while keeping all else constant, is proportional to the derivative with respect to field of the dc magnetostriction loop, i.e., $\mbi{\lambda (H)}$ . The theoretical analysis is supported by experimental results obtained on FeSiB wires and ribbons.

Fe82Si2B14C2 amorphous powder cores with low core loss and relatively high magnetic flux density were fabricated by cold pressing, and their superior magnetic properties were discussed by comparing with traditional Fe78Si9B13 amorphous powder cores. At f = 100 kHz and Bm = 0·1 T, the Fe82Si2B14C2 cores exhibited core loss ∼449 kW m−3, a value comparable to that of traditional Fe78Si9B13 ones. The permeability roughly kept constant, giving a value of ∼70, at frequency up to 1 MHz. Moreover, superior characteristics of permeability under dc bias field were also attained. The values of Fe82Si2B14C2 cores were ∼10% higher than those of Fe78Si9B13 at Hdc = 100 Oe because of the higher magnetic flux density of ∼1·64 T at 800 A m−1 (B800) for the Fe82Si2B14C2 alloy. Consequently, the above superior magnetic properties of Fe82Si2B14C2 amorphous powder cores indicate they could be potentially used to deal with the high output current in electrical power supplies.

(Pb0.87−0.07xBa0.10+0.07x)La0.02(Zr0.7Sn0.15Ti0.15)O3 ceramics with 0 ≤ x ≤1 were prepared by conventional solid-state reaction process, and their dielectric and electric field–induced pyroelectric properties were systemically investigated. Compared with conventional pyroelectric materials, (Pb0.87−0.07xBa0.10+0.07x)La0.02(Zr0.7Sn0.15Ti0.15)O3 ceramics exhibited higher pyroelectric coefficient and figure of merit, which are beneficial for the development of pyroelectric devices. The specimens with x = 0.65 showed good pyroelectric properties for practical applications. When a 500 V/mm dc bias field was applied, they showed the maximum pyroelectric coefficient of 12,200 μC/m2K and the figure of merit of 106 × 10−5 Pa−0.5 at 45 °C, which are larger than those observed from conventional pyroelectric materials. Improvement of pyroelectric property is beneficial for the development of infrared detectors.

The dc bias field-dependent piezoelectric coefficient d 33 of lead zirconate titanate ceramics (PZT5, PZT8 and P5H) were determined by a quasi-static method. It was found that piezoelectric coefficient d 33 was almost independent of positive dc bias field for PZT8 and PZT5 ceramics, while for P5H ceramic an obvious decrease of coefficient d 33 was observed under positive dc bias field. On the other hand, the temperature-dependent piezoelectric response for PZT ceramics were investigated by both quasi-static and resonance methods. The piezoelectric coefficient d 33 was found to increase with increasing temperature for both PZT5 and PZT8 ceramics. For P5H ceramics, coefficient d 33 showed a first decreasing and then increasing tendency with respect to temperature. These results were discussed in terms of intrinsic and extrinsic contributions to piezoelectric response.

Measured results of magnetoelectric (ME) and converse magnetoelectric (CME) effects of TbxDy1−xFe2−y/Pb(Mg1/3Nb2/3)(1−x)TixO3/TbxDy1−xFe2−y (TD/PMNT/TD) and PMNT/TD/PMNT laminated composites are presented. ME effect was determined by measuring laminate voltage output under a Helmholtz-generated AC field biased by a DC field (0–1 kOe) (1 Oe = 79.58 A/m). The CME effect was measured by recording the voltage induced in a solenoid encompassing the ME sample while exposed to a DC bias field and PMNT layer driven by a 10 V AC source. The ME and CME responses in the two laminated structure are linear. The highest values of ME coefficients in TD/PMNT/TD and PMNT/TD/PMNT composites are 384 mV/Oe and 158 mV/Oe, respectively, while the highest values of CME coefficients in the two composites are 118 mG/V and 162 mG/V (1 G=10−4 T), respectively.

We have investigated the magnetic behaviour of a sintered YBCO sample by ac susceptibility measurements in the presence of a static bias dc magnetic field. Calculations of the imaginary part of the ac susceptibility or hysteresis losses have been performed to account for the measured ac loss valley. Our calculations based on the critical state model with j c = α ( T )/ B n reproduce the experimental data quite well. We also explored the effect of temperature exponent in the pinning strength parameter on the ac loss valley behaviour.

The effect of La3+ and Zn2+ codoping on the microstructure and dielectric properties in the 0.9Pb(Mg1/3Nb2/3)O3-0.1 PT ceramics was studied. Raman spectroscopy was used to study the small changes of ordering degree. The relative dielectric constant change with DC bias field was measured. When 2 mol. % La3+ and 3 mol. % Zn2+ was codoped, two dielectric peaks were observed in the temperature dependence of the dielectric constant. The maximal relative dielectric constant change decreased from 70.46% to 23.15% at 10 kHz (0∼1000 V/mm). The La3+ and Zn2+ codoping markedly increased the temperature and electric field stability of 0.9Pb(Mg1/3Nb2/3)O3-0.1PT ceramics.

The MnO2 doped 0.9PMN-0.1PT ceramics were prepared by the columbite precursor method. The dielectric properties and dc bias characteristics of all the specimens were investigated. The results showed that the maximum dielectric constant decreased with increasing MnO2 content. A maximum in the curves of dielectric constant for MnO2 doped specimens was observed at temperatures below T m under a dc bias field. The mechanism of the behaviors observed was tentatively discussed in terms of internal bias field.

The dielectric properties of (Pb0.85Ba0.11La0.03)(Zr0.76Sn0.20Ti0.04) (PLZST–B11) composite ceramics have been investigated systematically. The characteristic of PLZST–B11 was that it demonstrated antiferroelectricity. The dielectric constant increased, then decreased sharply with increasing DC electric field, and a low loss also was obtained under DC electric fields (≤40 kV/cm). The low loss (tan δ ~0.003) and the highest tunability (~65%) were obtained for the PLZST–B11 ceramics around 50°C, indicating that it is a promising candidate for bi-tunable materials nearby room temperature. The dielectric properties of PLZST–B11 composites under a DC bias field can be useful for the design of devices and practical applications.

We have studied the magnetoelectric coupling in ZnO films deposited on Metglas substrates. Highly c-axis oriented ZnO films were successfully deposited using pulsed laser deposition at a low temperature of 300 °C. High quality films with low surface roughness of 2.82 nm and thicknesses of about 2 μm were obtained. A large converse magnetoelectric coef- ficient of 3 × 10–6 s/m and a direct magnetoelectric coefficient of 47 mV/cm Oe at a low dc bias field of 17 Oe and frequency of 1 kHz were obtained by dynamic converse and direct magnetoelectric measurements, respectively. Our results demonstrate a significant magnetoelectric coupling in these layers. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

By using free standing film of ferroelectric liquid crystals, we can realize a system with finite size along helical axis. The dynamics of free-standing film of FLCs has been studied by electrooptical measurement under weak sinusoidal electric field with dc bias field not to occur the switching of directors. We have measured the electrooptical spectra by varying the thickness of film L and the ratio of L to helical pitch P by changing temperature. The obtained spectra make good agreement with those predicted theoretically by Urbank and Zeks. In most cases, two relaxation modes are observed in the spectra. The relaxation frequency of the faster mode slightly varies around 1kHz and that of the slower mode varies largely with the ratio L/P.

Barium strontium titanate (BST) thick films for use in frequency agile microwave circuit applications have been investigated. A potentially cost-effective processing route has been used to make BST thick films from mixed-oxide powders. BST thick films have been press-formed in a single step onto alumina substrates from a viscous polymer tape. Films with thicknesses ranging from 10 to 140 μm have been obtained. The microstructure and dielectric properties of the BST thick films have been characterised. The results show that Ba 0.7 Sr 0.3 TiO 3 thick films exhibit ∼20% tunability at room temperature under a DC bias field of 5.5 kV/cm. Possibilities for further improvements are discussed in terms of reducing the interactions between the BST films and alumina substrates.

The ferrielectricity and domain structures of the chiral smectic Cβphase (SmCCβ*) in antifer-roelectric liquid crystals were investigated. The real part of complex dielectric constant e′ in SmCβ* shows two-step decrease with increasing DC bias field. Each decrease corresponds to the suppression of relaxational two modes: one is the ferroelectric Goldstone mode and the other is a new mode induced by DC bias field. The relaxational frequency of the latter mode is nearly the same as that of chiral smectic Cαphase (SmCα*). Another mode was observed at the field strength where e′ shows steeply decrease. This mode may be attributed to the boundary motion between domains or phases. Three peaks of the switching current were observed in SmCβ* and also in the lower-temperature region of SmCα*. The peak positions are continuously linked to those of SmCα*. It can be said that the antiferroelectric ordering of SmCα* may appear as domains even in SmCβ* by electric bias field.

An asymmetrical and sensitive magneto-impedance (MI) effect was obtained in crossed anisotropy sputtered films magnetized with a dc-biased ac current. The crossed anisotropy amorphous films (CoFeB) were made on glass substrates using a dc sputtering with two layers of 4.5 μm thickness each applying a dc field of 270 Oe along with designed anisotropy direction. A linear MI characteristic with the field detection sensitivity of 12%/Oe was obtained, which creates a sensitive linear field sensor without any dc bias field.

Analytical expressions for the transmission coefficient and the resonance condition are derived for the first time for the asymmetrical rectangular double-barrier structures with deep well when a dc bias field is applied. It is found that the unity resonance of the resonant tunneling with unity transmission occurs when both the phase difference condition for resonance (PDCR) and the maximum condition for the peak value (MCPV) hold simultaneously, while the under-unity resonance occurs that the peak value of transmission coefficient at resonance is below unity if only PDCR holds. Wave functions of an electron at the resonance level are calculated and the confining phenomena are confirmed.

For the study of magnetic properties of sintered high-Tc ceramic superconductors, we measured harmonic ac susceptibilities Xn = Xn' - ixn" of Bi1.6Pb0.4Sr2Ca2Cu3Oy immersed in an external field H(t) = H'dc + Haccos(ωt), where Hdc (≥ 0) is a dc bias field and Hac (> 0) is an ac field amplitude. Measurements of Xn were carried out for n = 1, 2, 3, 5, 7, 9 and μOHac = 0.01-0.1 mT. The fundamental frequency used was 132 Hz. The observed results were analyzed within the construct of the Kim-Anderson model for critical-current density. Similar to our previous work for an YBa2Cu3Oy sample with Fe impurities, generation of the higherharmonic susceptibilities seems to arise from the supercurrent according to the same model. Details of the measurement and the analysis are presented.

The dielectrically observed Goldstone mode in ferroelectric liquid crystals is shown to have, beside the well-known DC bias field dependence, a strong AC field dependence of the dielectric loss. This non-linearity arises at AC field strengths > 100 V/cm already in the materials which we have studied. It is maximal at the frequency of maximum loss of the Goldstone mode and levels off at frequencies far enough apart. Thus attempts to analyse the Goldstone mode within the framework of the linear response theory are not applicable in general, but are restricted to sufficiently small AC fields.

Nonlinear dynamic responses of intermittency and period doubling are observed from the RLC nonlinear circuit of thiourea crystal. Nonlinear dynamic characteristics of thiourea was found to change when DC bias field was applied. The DC bias field effect was elaborated to find the nonlinear dependence of dielectric constant and relaxation time on bias field in thiourea crystal.

An asymmetrical and sensitive magneto-impedance effect was realized in twisted FeCoSiB and CoSiB amorphous wires magnetized with a dc-biased ac current, in impedance up to about 120%/Oe. The asymmetrical magneto-impedance (AMI) is useful to construct linear field sensors without any dc bias field. Mechanisms of the AMI are also discussed.

The piezoelectric d coefficients of oriented (1-x)Pb(Zn/sub 1/3/Nb/sub 2/3/)O/sub 3/-xPbTiO/sub 3/ single crystals for x = 0.045 and x = 0.08 (PZN-4.5%PT and PZN-8%PT) have been measured as functions of DC bias field and frequency using a Zygo laser interferometer system. The d coefficients decreased as the DC bias was increased, perhaps because of domain wall clamping due to the bias field. The d coefficients were also found to decrease with the increase of frequency; this frequency dependence decreased at sufficiently large bias fields. High d/sub 15/ values (/spl sim/2800 pC/N for PZN-4.5%PT and /spl sim/3300 pC/N for PZN-8%PT) were measured, which may make these oriented crystals promising candidates for high performance shear transducers.

The nonlinear dielectric response of ${\mathrm{SrTi}}^{18}{\mathrm{O}}_{3}$ is measured as a function of temperature and dc bias field strength. In the low-field region the nonlinearity coefficient ${\ensuremath{\chi}}_{3}/{\ensuremath{\chi}}_{1}^{4}$ is found to strongly decrease when approaching ${T}_{c}\ensuremath{\approx}25\mathrm{K}.$ This corroborates the existence of a fluctuation-controlled quantum ferroelectric phase transition despite its smearing due to quenched random fields and excludes a random-bond random-field cluster glass mechanism. Classic field scaling applies to temperatures $Tg{1.1T}_{\mathrm{c}}.$

Measurements of DC susceptibility, AC susceptibility, and AC susceptibility with an applied DC bias field were performed on mechanically milled GdAl2. A paramagnetic phase exists above a temperature T ≈ 140 K. However, there are significant deviations from the Curie-Weiss Law in this temperature regime, suggesting multiple magnetic components. Fits to the high temperature data show that two Curie-Weiss terms represent the data quite well. Below 140 K one of these magnetic components becomes ferromagnetic as indicated by a shoulder in the AC susceptibility and DC susceptibility data. This ferromagnetic component is suppressed by the application of sufficiently strong DC bias field. Accompanying this shoulder is a peak at lower temperatures (T < 50 K), which suggests the existence of another component that is magnetically glassy in nature. The two-component behavior of mechanically milled GdAl2 can be explained in terms of the nanostructure of the material, which consists of nanometer-sized grains and a disordered interphase.

The temperature-dependent polarization of SrTiO3 thin films is investigated using confocal scanning optical microscopy. A homogeneous out-of-plane and an inhomogeneous in-plane ferroelectric phase are identified from images of the linear electro-optic response. Both hysteretic and nonhysteretic behavior are observed under a dc bias field. Unlike classical transitions in bulk ferroelectrics, local ferroelectricity is observed at temperatures far above the dielectric permittivity maximum. The results demonstrate the utility of local probe experiments in understanding inhomogeneous ferroelectrics.

We study the phenomenon of negative differential conductance (NDC) in Bloch miniband superlattices originally predicted by (1970). For device purposes, it is important to characterize transport in a small-signal ac electric field superposed on a dc bias field. We report here the results of a theoretical study carried out for a GaAs-based planar superlattice. Employing a microscopic balance equation formulation, we include all dissipative-scattering mechanisms and relatively strong electron-electron interactions (Lei et al., 1991, 1992, 1993a, 1993b; Lei, 1992a, 1992b). Relaxation-time approximations are not used.

The magnetic sensitivity to magnetic field for the magnetoelectric (ME) sensor is studied. Theoretical analysis predicts that the ME voltage sensitivity to Hac (i.e., ∂VME/∂Hac under dc bias field) and the ME voltage sensitivity to Hdc (i.e., ∂VME/∂Hdc under ac bias field) for the ME sensor are significantly dependent on the product of the effective mechanical quality factor of the ME sensor Qm, the saturation magnetostriction λs of the magnetostrictive material, and the square of magnetic permeability μr. The experimental results demonstrate that the greatest value of ∂VME/∂Hac for the FeCuNbSiB/PZT-8/FeCuNbSiB (FePFe) sensor reaches 10 V/Oe due to the largest product of the Qm, λs and the square of μr, relative to FeNi-FACE/PZT-8/FeNi-FACE (FPF) and Terfenol-D/PZT-8/Terfenol-D (MPM) sensors. Meanwhile, the maximum value of ∂VME/∂Hdc for FePFe sensor achieves 242.2 mV/Oe, which is ∼10 times higher than that of the FPF sensor and ∼ 4 times higher than that of the MPM sensor. To obtain the high magnetic se...

In this investigation, rapidly quenched ribbons prepared by a melt spinning technique have been used as a magnetostrictive sensor (MsS) element for the generation and detection of guided waves traversing through a pipe. The materials we have used in the present study are the rapidly quenched Fe80Si8B12 and Fe40Ni40B20 which have a high magnetostriction constant. The experiments were conducted on a bare Al tube after generating proper dispersion curves. The experiments were carried out using as-spun and annealed ribbons. After optimizing the AC magnetizing field, DC bias field and frequency (from software), longitudinal guided waves were generated in the tubes using MsS ribbons. Measurements were carried out to test the sensitivity of this sensor to both circumferential discontinuity (saw cut) and defect free bare aluminum tubes at a frequency of 76?kHz. The effect of defect size on the sensor signal was also investigated. Using the present technique, the defects were not only identified but their location in the pipe was also estimated.

Polarization and Raman measurements, in KTa1-XNbX O3 (KTN), have shown the existence of precursor effects many degrees above the transition. These effects are due to the formation of polar nanoregions, or clusters, which also explain the departure of the susceptibility from its Curie-Weiss dependence at high temperature. It was also shown through ultrasonic measurements at high temperatures and concentrations that the clusters behave as dynamical polar fluctuations resulting in a softening of C11 with a (T-Tc)-0.5 dependence. In order to investigate the coupling between these polar fluctuations and the elastic strains of the solid, measurements of the elastic constants have been made for applied DC fields in the direction of propagation. Results are presented for C 11 and C44 in concentrations up to 16% Nb. These measurements have been extended through the transition where evidence has been found to support the existence of three transitions even at the lowest concentration

A microstripline pulse field system that allows the switching speed of high coercivity magnetic media to be measured with pulse widths t>or=0.64 ns is discussed. The results for gamma Fe/sub 2/O/sub 3/ are in good agreement with the previous work of Thornley and Williams (1974). A DC bias field H/sub B/ was added to the pulse field to allow the high coercivity samples to be switched from saturation to zero remanence and the results analyzed in terms of the switching constant S/sub w/. At H/sub B/=400 Oe, S/sub w/(Co- gamma Fe/sub 2/O/sub 3/)=158 ns-Oe; at H/sub B/=700 Oe, S/sub W/ (barium ferrite)=135 ns-Oe; at H/sub B/=720 Oe, S/sub W/ (metal particle)=84 ns-Oe. The value of S/sub W/ increased with decreasing bias field, particularly for barium ferrite, indicating that in zero bias barium ferrite tapes it would be a factor of three slower than metal particle tapes. >

Radio-frequency measurements of dynamic magnetic susceptibility of various ferromagnets show striking differences between local-moment ferromagnetism (LFM) and weak itinerant ferromagnetism (IFM) ferromagnetic systems. LFMs show a very sharp peak in susceptibility in the vicinity of the Curie temperature TC that rapidly decreases in amplitude and shifts to higher temperature with the application of a weak dc bias field. In stark contrast, the generally accepted IFM systems show no peak, but rather a broad maximum well below TC. The temperature of this maximum shifts to lower values and the amplitude is suppressed with an applied dc field.

Phase transformation and pyroelectric behavior of Pb(Nb,Zr,Sn,Ti)O3 (PNZST) and (Pb,La)(Zr,Sn,Ti)O3 (PLZST) antiferroelectric (AFE) thin films were investigated as a function of temperature and dc bias field. A large pyroelectric coefficient of the order of ∼3×10−7Ccm−2K−1 was realized at the ferroelectric (FE) to AFE and the AFE to FE phase transformations in the PLZST and PNZST films, respectively. The phase transformation temperature could be readily adjusted by dc bias for both films. The large pyroelectric coefficient combined with excellent dc tunability at the phase transformation temperature makes these two systems promising candidates for uncooled tunable pyroelectric thermal sensing applications.

Permittivity versus temperature characteristics and Curie–Weiss exponent (CWE) γ in the universal Curie–Weiss law [e−1=em−1[1+(T−Tc)γ∕(2δ2)](1⩽γ⩽2)] as a function of dc bias field were obtained for ⟨001⟩, ⟨011⟩, and ⟨111⟩ oriented 0.76Pb(Mg1∕3Nb2∕3)O3–0.24PbTiO3 single crystals. Results indicated that γ is a function of dc bias field and three different oriented crystals show slight different γ values but the similar dc field dependence.

Dielectric properties in TFMHPOBC (4-(1,1,1-trifluoromethyl-heptyloxycarbonyl) phenyl 4'-octyloxybiphenyl-4-carboxylate) have been investigated as functions of temperature and dc bias field. In the antiferroelectric phase under no bias field, relaxation due to the soft mode and molecular rotation around the short axis are observed. Under dc bias field, a new relaxation is observed in chiral smectic CA (Sm CA *). The dielectric strength of this relaxation depends on the bias field, while the relaxation frequency is not affected by the dc bias field.