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Multiferroics that simultaneously exhibit ferroelectricity and ferromagnetism have recently attracted great attention due to their potential application in next generation electronic devices. However, only a few single-phase multiferroic materials exhibit ferroelectric and ferromagnetic orders at room temperature. Recently, some bismuth layer-structured Aurivillius compounds were reported as multiferroics at room temperature, but the origin of their magnetic property is still under debate because the net magnetization may originate from the presence of secondary phases that are not easily detected by laboratory XRD diffractometers. Here, textured Aurivillius phase Bi5.25La0.75FeCoTi3O18 ceramics were prepared by Spark Plasma Sintering. The ferromagnetic character of the ceramics was indicated by the magnetic field-induced reversible intensity changes of a certain set of crystalline planes belonging to the Aurivillius phase, as measured by in situ neutron diffraction under the applied magnetic field. The first principles calculations indicate that the ferromagnetism originates from double exchange interactions Fe3+–O–Fe3+, Co3+–O–Co3+, and Fe3+–O–Co3+ in the ferro-toroidal main phase. The magnetic-controlled ferroelectric domain switching was observed by piezoelectric force microscopy at room temperature. The prepared Aurivillius phase ceramics, with Co/Fe contributing to magnetization and polarization at the same time, can be considered an intrinsic room-temperature multiferroic.

A new materials characterization system developed at the XMaS beamline, located at the European Synchrotron Radiation Facility in France, is presented. We show that this new capability allows to measure the atomic structural evolution (crystallography) of piezoelectric materials whilst simultaneously measuring the overall strain characteristics and electrical response to dynamically (ac) applied external stimuli.

Here, we study the piezoresponse of epitaxial ferroelectric samples excited through top electrode structures with conductive tips in the global excitation mode and compare these results to displacement values obtained using artifact-free laser Doppler vibrometry (LDV) measurements. Substrate bending modes are studied using finite element simulations and LDV measurements and found to be negligible for top electrode diameters below 100 μm. The effect of electrostatic forces on the piezoresponse measurements is analyzed and methods for minimizing these are discussed. Using a resistive tip-electrode contact mode, the piezoresponse measurements are found to be in good agreement with values obtained from calibrations, providing a link between nanometer scale piezoresponse measurements and quantitative LDV measurements.

Jenny Wooldridge, John F. Blackburn, Neil L. McCartney, Mark Stewart, Paul Weaver et al. Citation: J. Appl. Phys. 109, 079901 (2011); doi: 10.1063/1.3572036 View online: http://dx.doi.org/10.1063/1.3572036 View Table of Contents: http://jap.aip.org/resource/1/JAPIAU/v109/i7 Published by the AIP Publishing LLC.

The ability to dynamically tune the coercive field of magnetic thin films is a powerful tool for applications, including in magnetic recording disk technologies. Recently, a number of papers have reported the electrical voltage control of the coercive field of various magnetic thin films in multiferroic composites. Theoretically, this is possible in magneto-electric (ME) multiferroics due to the piezoferroelectric component that can be electrically activated to dynamically modify the properties of the magnetic component of the composite via a direct or strain mediated ME coupling. In this paper we fabricated and examined such structures and we determined that the magnetic coercive field reduction is most likely due to a heating effect. We concluded that this effect is probably an artifact that cannot be attributed to a multiferroic coupling.

The functional properties of ferroelectric ceramic bulk or thin film materials are strongly influenced by their nanostructure, crystallographic orientation, and structural geometry. In this paper, we show how, by combining textural analysis, through electron backscattered diffraction, with piezoresponse force microscopy, quantitative measurements of the piezoelectric properties can be made at a scale of 25 nm, smaller than the domain size. The combined technique is used to obtain data on the domain-resolved effective single crystal piezoelectric response of individual crystallites in Pb(Zr0.4Ti0.6)O3 ceramics. The results offer insight into the science of domain engineering and provide a tool for the future development of new nanostructured ferroelectric materials for memory, nanoactuators, and sensors based on magnetoelectric multiferroics.

The recent trend in miniaturization of piezoelectrically active devices is driving research on size effects of these functional materials under reduced length scales. In this paper, we measure and model the generation of charge in thin piezoelectric structures under sinusoidal hydrostatic pressure and show how the subsequent thermally induced pyroelectric effect dominates the response in the smallest samples. We calculate the temperature profiles through the lead zirconate titanate structures, and determine the pyroelectric coefficient in these materials to be p′=0.28±0.02 mC m−2 K−1. The analysis of the piezoelectric and pyroelectric charge response described in this paper has significant impact on the design and fundamental functional behavior of small-scale piezoelectric devices.

The temperature dependence of the strain, electric field, and polarization of lead zirconate titanate ceramic under unipolar electric fields up to 1.3 kV mm−1 from −50 °C up to +200 °C is reported. An electrostrictive model is shown to describe the response to high levels of induced polarization and electric field below and above the ferroelectric to paraelectric transition. This is despite nonlinearity and hysteresis in the strain–field response. A linear strain–polarization response is shown to be an approximation to a quadratic electrostriction which is invalid at higher temperatures while the electrostriction holds across the temperature range.