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Register a new userOrigin of the magnetoelectric coupling effect in Pb(Zr0.2Ti0.8)O3/La0.8Sr0.2MnO3 multiferroic heterostructures
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The electronic valence state of Mn in Pb(Zr0.2Ti0.8)O3/La0.8Sr0.2MnO3 multiferroic heterostructures is probed by near edge x-ray absorption spectroscopy as a function of the ferroelectric polarization. We observe a temperature independent shift in the absorption edge of Mn associated with a change in valency induced by charge carrier modulation in the La0.8Sr0.2MnO3, demonstrating the electronic origin of the magnetoelectric effect. Spectroscopic, magnetic, and electric characterization shows that the large magnetoelectric response originates from a modified interfacial spin configuration, opening a new pathway to the electronic control of spin in complex oxide materials.
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In this article the mechanism of the linear magnetoelectric (ME) effect in the rhombohedral multiferroic BiFeO$_3$ is considered. The study is based on the symmetry approach of the GinzburgLandau type, in which polarization, antiferrodistortion, and antiferromagnetic momentum vectors are viewed as ordering parameters. We demonstrate that the linear ME effect in BFO is caused by reorientation of the antiferrodistortion vector in either electric or magnetic field. The numerical estimations, which show quantitative agreement with the results of the recent measurements in film samples, have been performed. A possibility of significant enhancement of the magnetoelectric effect by applying an external static electric field has been investigated. The considered approach is promising for explaining the high values of the ME effect in composite films and heterostructures with BFO.
Ferroelectric switching and nanoscale domain dynamics were investigated using atomic force microscopy on monocrystalline Pb(Zr0.2Ti0.8)O3 thin films. Measurements of domain size versus writing time reveal a two-step domain growth mechanism, in which initial nucleation is followed by radial domain wall motion perpendicular to the polarization direction. The electric field dependence of the domain wall velocity demonstrates that domain wall motion in ferroelectric thin films is a creep process, with the critical exponent mu close to 1. The dimensionality of the films suggests that disorder is at the origin of the observed creep behavior.
We theoretically study magnetoelectric effects in a heterostructure of a generic band insulator and a ferromagnet. In contrast to the kinetic magnetoelectric effect in metals, referred to as the Edelstein effect or the inverse spin galvanic effect, our mechanism relies on virtual interband transitions between the valence and conduction bands and therefore immune to disorder or impurity scattering. By calculating electric field-induced magnetization by the linear response theory, we reveal that the magnetoelectric effect shows up without specific parameter choices. The magnetoelectric effect qualitatively varies by changing the direction of the magnetic moment in the ferromagnet: the response is diagonal for the out-of-plane moment, whereas it is off-diagonal for the inplane moment. We also find out that in optical frequencies, the magnetoelectric signal can be drastically enhanced via interband resonant excitations. Finally, we estimate the magnitude of the magnetoelectric effect for a hybrid halide perovskite semiconductor as an example of the band insulator and compare it with other magnetoelectric materials. We underscore that our mechanism is quite general and widely expectable, only requiring the Rashba spin-orbit coupling and exchange coupling. Our result could potentially offer a promising method of Joule heating-free electric manipulation of magnetic moments in spintronic devices.
Pb(Fe$_{0.5}$Nb$_{0.5}$)O$_3$ (PFN), one of the few relaxor multiferroic systems, has a $G$-type antiferromagnetic transition at $T_N$ = 143 K and a ferroelectric transition at $T_C$ = 385 K. By using high-resolution neutron-diffraction experiments and a total scattering technique, we paint a comprehensive picture of the long- and short-range structures of PFN: (i) a clear sign of short-range structural correlation above $T_C$, (ii) no sign of the negative thermal expansion behavior reported in a previous study, and (iii) clearest evidence thus far of magnetoelectric coupling below $T_N$. We conclude that at the heart of the unusual relaxor multiferroic behavior lies the disorder between Fe$^{3+}$ and Nb$^{5+}$ atoms. We argue that this disorder gives rise to short-range structural correlations arising from O disorder in addition to Pb displacement.
Magnetic, dielectric and calorimetric studies on 0.9BiFeO3-0.1BaTiO3 indicate strong magnetoelectric coupling. XRD studies reveal a very remarkable change in the rhombohedral distortion angle and a significant shift in the atomic positions at the magnetic Tc due to an isostructural phase transition. The calculated polarization using Rietveld refined atomic positions scales linearly with magnetization. Our results provide the first unambiguous evidence for magnetoelectric coupling of intrinsic multiferroic origin in a BiFeO3 based system.
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