We report studies of the ferroelectric and magnetic phase transitions of (1 – x)­Pb­(Fe0.5Nb0.5)­O3 – xCo0.65Zn0.35Fe2O4 (x = 0.2) composite with emphasis upon the nature of magnetoelectric coupling at room temperature. The presence of all cationic elements with their required stoichiometry have been confirmed by SEM and XPS studies. The composite shows well-saturated ferroelectric and ferromagnetic (multiferroic) behavior at room temperature. A ferroelectric-paraelectric phase transition has been confirmed from the temperature dependent dielectric spectra along with DSC and Raman spectroscopic studies. Antiferromagnetic, ferromagnetic, and relaxor paramagnetic states have been observed in this composite. This composite shows strong bulk biquadratic magnetoelectric coupling at room temperature, which can be useful for potential multifunctional device applications.

Palladium normally does not easily substitute for Ti or Zr in perovskite oxides. Moreover, Pd is not normally magnetic (but becomes ferromagnetic under applied uniaxial stress or electric fields). Despite these two great obstacles, we have succeeded in fabricating lead zirconate titanate with 30% Pd substitution. For 20:80 Zr:Ti the ceramics are generally single-phase perovskite (>99%), but sometimes exhibit 1% PbPdO2, which is magnetic below T=90K. The resulting material is multiferroic (ferroelectric-ferromagnet) at room temperature. The processing is slightly unusual (>8 hrs in high-energy ball-milling in Zr balls), and the density functional theory provided shows that it occurs because of Pd +4 in the oversized Pb +2 site; if all Pd +4 were to go into the Ti +4 perovskite B-site, no magnetism would result.

No abstract

The search for a room temperature single phase multiferroic material displaying strong magnetoelectric coupling and low leakage current for practical device applications has been underway and a long-standing challenge. In continuation to our investigations for achieving robust ME coupling and enhanced electrical insulation at room temperature, we report magnetic, electrical insulation, and magneto-dielectric properties of Nd and Mn co-doped BiFeO3 (Bi0.95Nd0.05)(Fe0.97Mn0.03)O3 (BNFM) polycrystalline electro-ceramics. Magnetic studies have been carried out in two different temperature regions, i.e., 15–300 K and 300–800 K. The doping of Nd and Mn in the BiFeO3 (BFO) lattice slightly reduces the Néel temperature (TN) with broad weak ferromagnetic (FM) to paramagnetic (PM) phase transition by increasing ferromagnetic domain fractions. A small amount of magnetic frustration is also found in the low temperature regions, below 300 K at fields of 100 and 200 Oe, and below 200 K at higher field cooled and zero field cooled; this may be due weak long range ordering and small magnitude of magnetic moments. High temperature magnetic results imply the existence of a weak ferromagnetic phase with a FM to PM phase transition around 630 K (±5 K) and significant suppression of the spin frustration and canting properties of BFO. The Nd and Mn co-doping also substantially improved the electrical insulating properties of BFO. The leakage current analysis suggests that the Simmons' mechanism is probably a dominant conduction mechanism in BNFM at room temperature. The observation of dielectric anomaly around the TN and significant variation of dielectric parameters with different static magnetic field in BNFM implies the existence of strong magnetodielectric coupling. The enhanced magnetic and electrical insulation properties with strong magnetodielectric coupling at room temperature elucidate the possible potential candidates for multifunctional and spintronics device applications.

We demonstrate the control of solitary wave dynamics of modified Kortweg-de Vries (MKdV) equation through the temporal variations of the distributed coefficients. This is explicated through exact cnoidal wave and localized soliton solutions of the MKdV equation with variable coefficients. The solitons can be accelerated and their propagation can be manipulated by suitable variations of the above parameters. In sharp contrast with nonlinear Schrödinger equation, the soliton amplitude and widths are time independent.PACS numbers: 03.75. Lm,05.45.Yv, Modified Kortweg-de Vries (MKdV) equation manifests in diverse areas of physics [1,2,3,4,5,6]. For example, it appears in the context of, electromagnetic waves in size-quantized films, van Alfvén waves in collisionless plasma [7], phonons in anharmonic lattice [8], interfacial waves in two layer liquid with gradually varying depth [9], transmission lines in Schottky barrier [10], ion acoustic solitons [11,12,13], elastic media [14], and traffic flow problems [15,16]. It is an integrable dynamical system with an infinite number of conserved quantities; the solutions of this equation are well studied [17,18].