Search

Single-frequency piezoresponse force microscopy (PFM) images of a BiFeO3/DyScO3(110) thin film, obtained with long (kc = 0.82 N/m) and short (kc = 7.64 N/m) cantilevers, were analyzed as a function of the applied voltage frequency. For long cantilevers, the electrostatic and electrostrictive contributions were identified. These contributions were reduced with a frequency near the second mode of the contact resonance; while for short cantilevers, the first mode was necessary. A method for domain structure analyses, to discriminate a ferroelectric behavior from a non-ferroelectric, through the optimization of PFM images, is also described. The analysis can be extended to cantilevers with different spring constants and ferroelectric materials. [ABSTRACT FROM AUTHOR]

Using Raman spectroscopy, the study of a polymorphic phase transition in the KNNLiTaLa0.01 compound is presented. An analysis of the behavior with temperature, wavenumber and half width at full maximum of the individual bands, corresponding to the vibration modes of the (Nb/Ta)O6 octahedra of the KNNLiTaLa0.01 compound's structure, is performed. This analysis determined that the polymorphic phase transition of the KNNLiTaLa0.01 compound occurs in the 90 to 105°C temperature interval. Using the Hard Mode Spectroscopy method, the value of the critical exponent of the order parameter was determined to be β ≈ ½, indicative of a second order transition. [ABSTRACT FROM AUTHOR]

This theoretical work presents the electronic and magnetic properties of Cr doped SrFe12O19 using first-principles calculations based on density functional theory. An improvement in the magnetic properties of SrFe12O19 is predicted when doped with the Cr3+ ion. It was found that the magnetic Cr3+ ion preferentially replaces Fe3+ ion at 2a, 4f1, and 12k sites. The calculation demonstrates that if Cr ion occupies the 4f1 site, a total magnetization of 52.920 emu/g is obtained. On the other hand, SrFe11.5Cr0.5O19 behaves as a semiconductor when Cr occupies the 2a and 12k sites while behaves like half-metal when Cr occupies the 4f1 site. The higher magnetization, identified for the SrFe11.5Cr0.5O19 compound, provides unique qualities in the applications of permanent magnets and/or related devices like spintronics and magnetic semiconductors. [ABSTRACT FROM AUTHOR]

The c 66 E values of PZT53/47 doped with 0.6% Gd2O3 show an anomalous behavior near 132°C as a consequence of a ferroelastic transition. A non-linear fit to the experimental data of the elastic stiffness variation Δ c 66 E shows that it behaves according to the theoretical law describing pseudoproper ferroelastic transitions. Through Raman spectrum analysis, the frequency of soft mode A1(1TO) has a minimum in the 132–136°C temperature interval associated with the coupling to the S 6 component of the deformation. The quantitative evaluation of the order parameter by hard mode spectroscopy ratified the occurrence of a ferroelastic phase transition. The behavior of both piezoelectric coefficients d31 and the electromechanical coupling factor k31 can be taken as evidence of the transition showing local maxima at 138°C as a consequence of the maximum deformation during the oscillations of the A1(1TO) mode. [ABSTRACT FROM AUTHOR]

The orthoferrites with the general formula RFeO3 (R = Ho, Er, Lu, Sc, and Y) have recently attracted a great deal of attention because they are promising candidates for a second generation of multiferroic materials. In this computational work, the structural, ferroelectric and optical properties of the YFeO3 perovskite oxide (YFO) and a Bi‐doped YFeO3 were analyzed. Bi‐substitution in YFO leads to an increase of its lattice parameters by virtue of the larger ionic radius of Bi3+. Both compounds exhibit a G‐type antiferromagnetic ground state. The calculations disclose a significant spontaneous polarization along the [101] direction of YFO‐Bi, which originates in the asymmetric distribution of the charges around the Bi3+ ions, as a result of the Bi‐6s electrons. The electric polarizability of YFO is increased upon Bi3+‐doping and the more significant components of the real permittivity tensor of YFO‐Bi are those associated with the direction along which the maximum value of spontaneous polarization is observed. The spontaneous polarization of YFO‐Bi found in this work reveals that this compound holds the potential for the next generation of multi ferroic materials. [ABSTRACT FROM AUTHOR]