Recent research activities on the linear magnetoelectric (ME) effect?induction of magnetization by an electric field or of polarization by a magnetic field?are reviewed. Beginning with a brief summary of the history of the ME effect since its prediction in 1894, the paper focuses on the present revival of the effect. Two major sources for 'large' ME effects are identified. (i) In composite materials the ME effect is generated as a product property of a magnetostrictive and a piezoelectric compound. A linear ME polarization is induced by a weak ac magnetic field oscillating in the presence of a strong dc bias field. The ME effect is large if the ME coefficient coupling the magnetic and electric fields is large. Experiments on sintered granular composites and on laminated layers of the constituents as well as theories on the interaction between the constituents are described. In the vicinity of electromechanical resonances a ME voltage coefficient of up to 90?V?cm?1?Oe?1 is achieved, which exceeds the ME response of single-phase compounds by 3?5 orders of magnitude. Microwave devices, sensors, transducers and heterogeneous read/write devices are among the suggested technical implementations of the composite ME effect. (ii) In multiferroics the internal magnetic and/or electric fields are enhanced by the presence of multiple long-range ordering. The ME effect is strong enough to trigger magnetic or electrical phase transitions. ME effects in multiferroics are thus 'large' if the corresponding contribution to the free energy is large. Clamped ME switching of electrical and magnetic domains, ferroelectric reorientation induced by applied magnetic fields and induction of ferromagnetic ordering in applied electric fields were observed. Mechanisms favouring multiferroicity are summarized, and multiferroics in reduced dimensions are discussed. In addition to composites and multiferroics, novel and exotic manifestations of ME behaviour are investigated. This includes (i) optical second harmonic generation as a tool to study magnetic, electrical and ME properties in one setup and with access to domain structures; (ii) ME effects in colossal magnetoresistive manganites, superconductors and phosphates of the LiMPO4 type; (iii) the concept of the toroidal moment as manifestation of a ME dipole moment; (iv) pronounced ME effects in photonic crystals with a possibility of electromagnetic unidirectionality. The review concludes with a summary and an outlook to the future development of magnetoelectrics research.

https://iopscience.iop.org/article/10.1088/0022-3727/38/8/R01/pdf

Revival of the Magnetoelectric Effect

4.3. Manganese Oxide-Based Compounds 1291 4.3.1. MnO2-Type Compounds 1291 4.3.2. Ternary Lithiated LixMnOy Compounds 1293 4.4. Vanadium Pentoxide V2O5 1298 4.4.1. V2O5 Structure 1298 4.4.2. LixV2O5 Bulk Phases 1300 4.4.3. LixV2O5 Crystallized Thin Films 1303 4.5. Titanium Oxide-Based Compounds 1305 4.5.1. Lithium Titanate Li4Ti5O12 1306 4.5.2. TiO2 Anatase 1308 5. Phospho-olivine LiFePO4 Compound 1312 6. General Conclusion 1314 7. Acknowledgments 1315 8. References 1315

Raman Microspectrometry Applied to the Study of Electrode Materials for Lithium Batteries

We have investigated a wide variety of surfactants for their efficiency in dissolving isolated single-walled carbon nanotubes (SWNTs) in water. In doing so, we have completely avoided the harsh chemical or mechanical conditions, such as acid or ultrasonic treatments, that are known to damage SWNTs. Bile salts in particular are found to be exceptionally effective in dissolving individual tubes, as evidenced by highly resolved optical absorption spectra, bright bandgap fluorescence, and the unprecedented resolution (∼ 2.5 cm - 1 ) of the radial breathing modes in Raman spectra. This is attributed to the formation of very regular and stable micelles around the nanotubes providing an unusually homogeneous environment. Quantitative information concerning the degree of solubilization is obtained from absorption spectroscopy.

Efficient isolation and solubilization of pristine single-walled nanotubes in bile salt micelles

Presented theses criticize the hasty observations and conclusions about some toxic properties of various aqueous dispersions of C60 nanoparticles. In turn, a number of arguments are made emphasizing that pristine fullerenes are non‐toxic, but the supramolecular system of “fullerene‐water” has a wide spectrum of positive and unique biological activity.

Is the C60 Fullerene Molecule Toxic

Lithium-ion batteries have dominated the battery industry for the past several years in portable electronic devices due to their high volumetric and gravimetric energy densities. The success of these batteries in small-scale applications translates to large-scale applications, with an important impact in the future of the environment by improving energy efficiency and reduction of pollution. We present the progress that allows several lithium-intercalation compounds to become the active cathode element of a new generation of Li-ion batteries, namely the 5-V cathodes, which are promising to improve the technology of energy storage and electric transportation, and address the replacement of gasoline engine by meeting the increasing demand for green energy power sources. The compounds considered here include spinel LiNi0.5Mn1.5O4 and its related doped-structures, olivine LiCoPO4, inverse spinel LiNiVO4 and fluorophosphate Li2CoPO4F. LiNi0.5Mn1.5O4 thin films, nanoscale prepared materials and surface-modified cathode particles are also considered. Emphasis is placed on the quality control that is needed to guarantee the reliability and the optimum electrochemical performance of these materials as the active cathode element of Li-ion batteries. The route to increase the performance of Li-ion batteries with the other members of the family is also discussed.

Review of 5-V electrodes for Li-ion batteries: status and trends

Raman spectroscopy of HiPCO single-walled carbon nanotubes at 300 and 5 K

The complete Raman spectra of a single crystal of LiNiPO4 for a wide temperature range are reported. Of the 36 Raman-active modes predicted by group theory, 33 have been detected. The spectra are successfully analyzed in terms of internal modes of the (PO4)3− group and external modes. Multiphonon Raman scattering is also discussed. Low-frequency lines, observed in the antiferromagnetic phase, are assigned to magnon scattering and are discussed briefly.

/pdf/raman-scattering-in-a-linipo4-single-crystal-379tbv297n.pdf

Raman scattering in a LiNiPO4 single crystal

We performed Raman studies and a dielectric characterization of the pseudo-kagome Cu3Bi(SeO3)2O2X (X = Cl, Br). These compounds share competing nearest-neighbour ferromagnetic exchange and frustrating next-nearest-neighbour antiferromagnetic exchange as well as highly noncollinear magnetic ground state. However, at low temperature they differ with respect to the existence of inversion symmetry. For both compounds there exists a pronounced interplay of polar phonon modes with quantum magnetic fluctuations. A novel Raman mode appears for temperatures below the Neel temperature with a Fano lineshape and an enormous intensity that exceeds most of the phonon lines. We discuss a possible contribution of longitudinal magnons to this signal. In contrast, one magnon scattering based on linear transvers magnons is excluded based on a symmetry analysis of spin wave representations and Raman tensor calculations. There exists evidence that in these pseudo-kagome compounds magnetic quantum fluctuations carry an electric dipole moment. Our data as well as a comparison with previous far-infrared spectra allow us to conclude that Cu3Bi(SeO3)2O2Cl changes its symmetry most likely from Pmmn to P21mn with a second order structural phase transition at T*=120 K and becomes multiferroic. Cu3Bi(SeO3)2O2Br represents an interesting counter part as it does not show this instability and stays inversion symmetric down to lowest temperatures, investigated.

Longitudinal magnon, inversion breaking and magnetic instabilities in the pseudo-Kagome francisites Cu3Bi(SeO3)2O2X with X=Br, Cl

The low temperature anomaly of two-magnon Raman scattering is detected and studied experimentally in a NH3(CH2)2NH3MnCl4 crystal. A model of doubling the crystal magnetic cell is presented which makes it possible to explain qualitatively the effects observed.

Spin wave spectrum of quasi-two-dimensional antiferromagnet NH3(CH2)2NH3MnCl4

The IR reflectance spectra of the cubic noncentrosymmetric ferrimagnet Cu2OSeO3 (TC ≈ 60 K) were investigated in the temperature range 10–80 K. Detailed analysis of the symmetry and composition of vibrational modes was conducted on the basis of Raman scattering data and data obtained in this investigation. 68 out of 69 modes consistent with the crystal lattice symmetry were revealed. Some spectral features found in the magnetically ordered phase were studied. The bands at 280 and 421 cm−1 related to the spectrum of two-magnon light scattering were observed. Dynamic magnetoelectric coupling was found to be responsible for the intensity redistribution in the Raman and IR spectra for the threefold degenerate modes of F-symmetry (modes at 84, 205, and 269 cm−1). No change associated with magnetic ordering was observed in the symmetry of the crystal structure.

V. S. Kurnosov

Papers

Raman spectroscopy of HiPCO single-walled carbon nanotubes at 300 and 5 K

Raman scattering in a LiNiPO4 single crystal

Longitudinal magnon, inversion breaking and magnetic instabilities in the pseudo-Kagome francisites Cu3Bi(SeO3)2O2X with X=Br, Cl

Spin wave spectrum of quasi-two-dimensional antiferromagnet NH3(CH2)2NH3MnCl4

Analysis of the low-frequency spectrum of the cubic noncentrosymmetric ferrimagnet Cu2OSeO3