A manipulação elétrica das propriedades magnéticas é um problema-chave da pesquisa de materiais. Para atender aos requisitos da eletrônica moderna, esses processos devem ser alterados para altas frequências. Em materiais ferrosos, isso pode ser alcançado pelo controle elétrico e magnético de suas excitações fundamentais.
Electric and magnetic ordering in rare-earth iron borates. (a) Homogeneous distribution of Fe spins (blue arrows) in the ab plane and in the absence of static magnetic (H) and electric (E) fields. Different arrows refer to different domains in the sample. Both antiferromagnetic vector L and static polarization P equal zero in this case. (c),(d) Either magnetic field H∥b (c) or electric field E↑↑a (d) induce P↑↑a and L∥a. (e),(f) Rotation of the magnetic field to H∥a (e) or inversion of the electric field to E↑↓a (f) leads to the inversion of the static polarization and the rotation of the antiferromagnetic vector. Figure 1 shows the crystal structure of SmFe3(BO3)4
Aqui identificamos vibrações magnéticas em boratos de ferro que são simultaneamente sensíveis a campos elétricos e magnéticos externos. É demonstrada quase 100% de modulação da radiação.
Manipulation of magnon excitation by magnetic field. (a) Suppression of the magnon at 9 cm−1 in SmFe3(BO3)4 by external magnetic fields along the a axis. (b) Increasing of the mode intensity in magnetic fields H∥b axis. (c) Magnetic field dependence of the mode intensity from fitting the spectra in Figs. 2 and 2 by a Lorentzian function (blue and orange spheres, respectively) and from model calculation based on Eq. (2) (solid gray lines ). Manipulation of the magnon in SmFe3(BO3)4 by static electric field. (a) Transmittance amplitude and (b) phase shift spectra in the electric field. Symbols: green, initial state; blue, negative electric field; and red, positive electric field. The black line demonstrates that an external magnetic field can approximately compensate the effect of the electric field. (c) Direct modulation of the transmittance amplitude signal by a static electric field at different frequencies. The inset shows the temperature dependence of the resonance frequency as observed (dark gray line) and calculated (light gray line) in Ref. [62]. The temperatures and frequencies of the transmittance amplitude measurements are marked in the inset by circles. (d) Changes in magnon contribution in the electric field. Symbols are experimental results, while the solid lines come from model calculation based on Eq. (2). The orange and blue symbols correspond to a simultaneous application of electric and magnetic fields . Electric field effect in NdFe3(BO3)4. (a) Temperature dependence of the relative transmittance amplitude signal for different frequencies. Weak sawtooth modulation of the curves is due to ±500 V sweeping of electric voltage during the cooling process. The inset shows the temperature dependence of the resonance frequency as observed (dark gray line) and calculated (light gray line) in Ref. [62]. The temperatures and frequencies of the resonances seen in (a) are marked in the inset by circles. (b) An example of a detailed view of the data in (a). Here the spectra are normalized by the minimal transmitted intensity. (c) Direct modulation of the terahertz transmittance amplitude at selected frequencies in NdFe3(BO3)4
A alta sensibilidade pode ser explicada por uma modificação da orientação da rotação que controla as condições de excitação em boratos ferrosos. Essas experiências demonstram a possibilidade de alterar propriedades magnéticas de materiais de forma independente por campos elétricos e magnéticos externos.
Artigo: Switching of Magnons by Electric and Magnetic Fields in Multiferroic Borates Autores: A. M. Kuzmenko, D. Szaller, Th. Kain, V. Dziom, L. Weymann, A. Shuvaev, Anna Pimenov, A. A. Mukhin, V. Yu. Ivanov, I. A. Gudim, L. N. Bezmaternykh, A. Pimenov Revista: Physical Review Letters Vol.: 120, 027203 DOI: 10.1103/PhysRevLett.120.027203
