Multiferroic means the coexistence of ferroelectricity, ferromagnetism, ferroelasticity, etc. Multi-ferrous materials and magneto-electro-mechanical coupling have rich basic physical problems and have important application prospect, Physics and materials science one of the hot spots.Multi-ferrous materials are divided into two types of composite materials and single-phase materials, the magnetic coupling of composite materials is the use of interface effect to achieve indirect coupling, magnetic coupling of single-phase material is the intrinsic It has been found that a wide variety of single-phase, multiferroic materials, the magneto-electric coupling effects of known single-phase multiferroic materials (magnetic field-controlled electrodeposition or field-controlled magnetism) are often relatively weak, limiting single phase How to greatly improve the magneto-electric coupling effect of single-phase materials has become a major challenge in this field recently.Historical Institute of Physics, Chinese Academy of Sciences / Beijing Condensed Matter Physics Laboratory ) Researcher Sun Yang et al. Implemented a tremendous magneto-electric coupling effect in a Y-type hexagonal ferrite Ba0.4Sr1.6Mg2Fe12O22 and obtained positive magneto-electric coupling coefficients of up to 33000ps / m and 32000p s / m, creating a new world record for the magneto-electric coupling effect of single-phase materials. The related research was published in Nature Communications.
Hexagonal ferrite is a type of iron-based oxide with a hexagonal system, which can be further divided into hexagonal ferrite M, W, X, Y, Z, and U according to the structural units. Due to the existence of various magnetic Interaction between hexagonal ferrite can be part of the replacement of elements to produce a rich non-collinear helical magnetic structure for some specific helical magnetic structure, the non-collinear spins can be inverse Dzyaloshinskii-Moriya interaction Resulting in the second kind of multi-ferromagnetic and magneto-electric coupling effect of macro-electrode polarization, which leads to magnetic orderly driving.In the past studies, strong magneto-electric coupling effect has been observed in some hexagonal ferrites. However, Hexagonal ferrite to further achieve a huge magneto-electric coupling effect, the lack of clear understanding and ideas.In order to understand the Y-type hexaferrite Ba0.4Sr1.6Mg2Fe12O22 giant magnetoelectric coupling effect of the physical origin, researchers synthesized Ba2 -xSrxMg2Fe12O22 (0.0≤x≤1.6) series of single-crystal samples, systematically studied the macroscopic magnetic and magneto-electric coupling effects with the Sr content changes at the same time, Sun Yang and Oak Ridge National Laboratory researchers The phase structure of the conical helical structure in Ba2-xSrxMg2Fe12O22 system with the content of Sr and the change of applied magnetic field was also studied by using neutron scattering technique. The results show that hexagonal iron The strength of the magnetoelectric coupling effect in oxygen is closely related to the symmetry of the spin cone. When the symmetry of the spin cone decreases from quadri-symmetry to double symmetry, the spin cone can be driven 180 Degree reversal; at the same time, the polarization of the spin structure will also occur 180 degrees reversal.Analysis of magnetic anisotropy through elemental replacement of the phase transition occurs near zero magnetic field, resulting in a huge magnetic coupling coefficient The maximum forward-reverse magneto-electro-magnetic coupling coefficient in single-phase materials so far has been obtained and the direction has also been pointed out for how to improve the magneto-electric coupling effect in multiferroic hexagonal ferrite.
The research work has been supported by the National Natural Science Foundation, the Ministry of Science and Technology and the Chinese Academy of Sciences.
