Search results for "Multiferroic"
showing 10 items of 46 documents
Effect of cobalt doping on the local structure and dynamics of multiferroic MnWO4and Mn0.7Co0.3WO4
2013
The local atomic structure and dynamics in multiferroic MnWO4 and Mn0.7Co0.3WO4 have been studied by X-ray absorption spectroscopy at the Co(Mn) K-edge and W L3-edge. The analysis of the first coordination shell of metal ions using single-shell Gaussian approximation and regularization-like method allowed us to determine a distortion of Mn(Co)O6 and WO6 octahedra. It was found that the local environment of Co2+ ions in Mn0.7Co0.3WO4 is close to that in CoWO4, whereas the presence of cobalt ions reduces the distortion of MnO6 octahedra in comparison with pure MnWO4.
NMR Study of Multiferroic Iron Niobate Perovskites
2015
NMR Study of Multiferroic Iron Niobate Perovskites K. Kou°il, V. Chlan, H. t¥pankova, R. ezni£ek, V.V. Laguta and I.P. Raevski Charles University in Prague, Faculty of Mathematics and Physics, V Hole2ovi£kach 2, 180 00 Prague 8, Czech Republic Institute of Physics AS CR, Cukrovarnicka 10, 162 00 Prague 6, Czech Republic Institute of Physics, Southern Federal University, Rostov on Don 344090, Russia We present Nb, Pb and Ba NMR study of multiferroic lead iron niobate and barium iron niobate ceramics. We ascribe development of NMR spectra on cooling below room temperature to magnetism of ferric ions close to resonating nuclei and introduce a framework capable of describing key features of t…
Lateral Electric‐Field‐Controlled Perpendicular Magnetic Anisotropy and Current‐Induced Magnetization Switching in Multiferroic Heterostructures
2020
Pressure effects on the electronic and optical properties ofAWO4wolframites (A =Cd, Mg, Mn, and Zn): The distinctive behavior of multiferroic MnWO4
2012
The electronic band-structure and band-gap dependence on the $d$ character of ${A}^{2+}$ cation in $A$WO${}_{4}$ wolframite-type oxides is investigated for different compounds ($A$ $=$ Mg, Zn, Cd, and Mn) by means of optical-absorption spectroscopy and first-principles density-functional calculations. High pressure is used to tune their properties up to 10 GPa by changing the bonding distances establishing electronic to structural correlations. The effect of unfilled $d$ levels is found to produce changes in the nature of the band gap as well as its pressure dependence without structural changes. Thus, whereas Mg, Zn, and Cd, with empty or filled $d$ electron shells, give rise to direct and…
The Ba2LnFeNb4O15 “tetragonal tungsten bronze”: Towards RT composite multiferroics
2009
Several Niobium oxides of formula Ba2LnFeNb4O15 (Ln = La, Pr, Nd, Sm, Eu, Gd) with the Tetragonal Tungsten Bronze (TTB) structure have been synthesised by conventional solid-state methods. The Neodymium, Samarium and Europium compounds are ferroelectric with Curie temperature ranging from 320 to 440K. The Praseodymium and Gadolinium compounds behave as relaxors below 170 and 300 K respectively. The Praseodymium, Neodymium, Samarium, Europium and Gadolinium compounds exhibit magnetic hysteresis loops at room temperature originating from traces of a barium ferrite secondary phase. The presence of both ferroelectric and magnetic hysteresis loops at room temperature allows considering these mat…
Local Structure of Multiferroic MnWO4 and Mn0.7Co0.3WO4 Revealed by the Evolutionary Algorithm
2015
A novel reverse Monte Carlo/evolutionary algorithm scheme was applied to the analysis of the W L3-edge and Mn(Co) K-edges EXAFS spectra from multiferroic MnWO4 and Mn0.7Co0.3WO4. A 3D structural model, consistent with the experimental data, was obtained, and the influence of composition and temperature on the local structure of tungstates is discussed.
Magnetic resonance study of bulk and thin film EuTiO3
2017
Magnetic resonance spectra of EuTiO3 in both bulk and thin film form were taken at temperatures from 3-350 K and microwave frequencies from 9.2-9.8 and 34 GHz. In the paramagnetic phase, magnetic resonance spectra are determined by magnetic dipole and exchange interactions between Eu2+ spins. In the film, a large contribution arises from the demagnetization field. From detailed analysis of the linewidth and its temperature dependence, the parameters of spin-spin interactions were determined: the exchange frequency is 15-15.5 GHz and the estimated critical exponent of the spin correlation length is ~ 0.5. In the bulk samples, the spectra exhibited a distinct minimum in the linewidth at the N…
Probing magnetism in 2D van der Waals crystalline insulators via electron tunneling
2018
Magnetic insulators are a key resource for next-generation spintronic and topological devices. The family of layered metal halides promises varied magnetic states, including ultrathin insulating multiferroics, spin liquids, and ferromagnets, but device-oriented characterization methods are needed to unlock their potential. Here, we report tunneling through the layered magnetic insulator CrI₃ as a function of temperature and applied magnetic field.We electrically detect the magnetic ground state and interlayer coupling and observe a fieldinducedmetamagnetic transition.The metamagnetic transition results in magnetoresistances of 95, 300, and 550% for bilayer, trilayer, and tetralayer CrI₃ bar…
Ultrafine MnWO4 nanoparticles and their magnetic properties
2015
Abstract Ultrafine nanoparticles of MnWO4, a compound showing low-temperature multiferroicity in the bulk, were synthesized by the polyol method. Studies using powder X-ray diffraction, scanning and transmission electron microscopy, dynamic light scattering, differential sedimentation and sorption techniques show the formation of a single-phase material, which is composed of MnWO4 nanoparticles with a prolate ellipsoidal shape (short axis of 4–5 nm, long axis of 11–12 nm) and an unprecedented high specific surface area of 166 m2 g−1. The as-prepared MnWO4 nanoparticles are readily crystalline after the liquid-phase synthesis. Temperature and field dependent magnetization measurements indica…
Conductance control at the LaAlO3/SrTiO3-interface by a multiferroic BiFeO3 ad-layer
2014
Multilayered BiFeO3 (BFO)/LaAlO3 (LAO) thin film samples were fabricated on SrTiO3 (STO) substrates by pulsed laser deposition. In this work, the ferroelectric polarization of a multiferroic BFO ad-layer on top of the quasi-two-dimensional electron gas (2DEG) at the LAO/STO interface is used to manipulate the conductivity of the quasi-2DEG. By microstructuring the conductive area of the LAO/STO-interface, a four-point geometry for the measurement of the resistivity was achieved. Piezo force microscopy allows for imaging and poling the spontaneous ferroelectric polarization of the multiferroic layer. The resistance changes showed a linear dependence on the area scanned and a hysteretic behav…