ME Response Research Articles

Magnetoelectric Properties of Multiferroic Composites with Pseudo 1-3 Type Structure

ABSTRACTA pseudo 1-3 type multiferroic composite consisting of Pb(Zr,Ti)O3 (PZT) rod array (with base) and Terfenol-D/Epoxy matrix was prepared by the dice-and-fill technique. Simple series and parallel mixture rules well described the measured dielectric and piezoelectric constants. Large magnetoelectric coefficients were observed in the pseudo 1-3 type composite, e.g., over 300 mV/cmi×Oe below 40 kHz and over 4500 mV/ cm×Oe at resonant frequency. The ME response strongly depends on the magnetostrictive behavior of the matrix and the volume fraction of PZT rods, which gives us two convenient way to modify their magnetoelectric response. For this pseudo 1-3 type multiferroic composite, the remarkable magnetoelectric response and well-developed fabrication technique are advantageous for their practical applications in piezoelectric-magnetoelectric multifunctional devices and large bandwidth magnetic sensors.

Influence of mechanical boundary conditions and microstructural features on magnetoelectric behavior in a three-phase multiferroic particulate composite

We report theoretical calculations of the magnetoelectric properties in a three-phase multiferroic particulate composite of Terfenol-D, lead-zirconate-titanate (PZT), and polymer based on the Green's function technique. Our results show that the values of the magnetoelectric voltage coefficients are very sensitive to mechanical boundary conditions that the composite sample suffers, and that the polarization orientation in PZT particles and the inactive interface layer surrounding PZT particles have a significant effect on the magnetoelectric behavior of the composite. The calculations well describe the recent observations and provide a general guideline for experimentally achieving large ME response of such multiferroic composites.

Magnetoelectric properties of LiCoPO 4: microscopic theory

The microscopic description of the magnetoelectric effect in LiCoPO 4 is given. The “one-ion” approximation in which the magnetic order is presented by a Weiss molecular field approximation is taken as the basis of the model. Using the lowest possible order of perturbation theory the mechanism analogous to that of the changes due to an electric field of g-factor rather than a mechanism which involves changes of the quadratic axial term (“D term”) in the spin-Hamiltonian is considered. Within the framework of the model it is shown that the odd part of the crystalline electric field and operator of the electric dipole transition can be represented by an effective operator with even parity that allows us a priori to take into account a parity selection rule. The expressions for the magnetoelectric tensor have been obtained. The theory may be applicable not only to the description of the static ME response but also to the description of the response of the system at optical frequencies.

Effect of refeeding raw and cooked starches on hepatic enzyme activities of rats.

1. Responses of hepatic glucose-6-phosphate dehydrogenase (EC 1.1.1.49; G6PD), malic enzyme (EC 1.1.1.40; ME), acetyl-CoA carboxylase (EC 6.4.1.2; ACAC), and fatty acid synthetase (FAS) were studied in male Wistar rats after a period of starvation and refeeding of diets containing 400 g glucose, or raw or cooked starches as the source of carbohydrate/kg. Starches fed included maize, potato, wheat, rice, and tapioca.2. When compared to the responses of rats given the glucose-containing diet, rats given raw maize- or rice-starch-containing diets had a significantly lower ME response, and rats given raw potato starch had significantly lower responses of G6PD, ME, ACAC, and FAS. The enzyme responses of rats given cooked starches were similar to those of glucose-fed rats, except that rats given cooked wheat starch had significantly lower G6PD and ME responses than did glucose-fed rats.3. When the enzyme responses to refeeding of the same starch source in either raw or cooked form were compared, it was found that (a) the FAS response was significantly higher to cooked than to raw maize starch, (b) the G6PD and ACAC responses were significantly higher to cooked than to raw tapioca starch, (c) the G6PD, ME, ACAC, and FAS responses were significantly higher to cooked than to raw potato starch.4. The results suggest that reported differences in the lipogenic enzyme responses between simple sugars and starch may in some instances be magnified because of the use of uncooked starches in experimental diets.