Room temperature multiferroicity in Bi4.2K0.8Fe2O9+δ

Abstract

Magnetoelectric multiferroics are materials that have coupled magnetic and electric dipole orders, which can bring novel physical phenomena and offer possibilities for new device functions. In this report, single-crystalline Bi4.2K0.8Fe2O9+δ nanobelts which are isostructural with the high-temperature superconductor Bi2Sr2CaCu2O8+δ are successfully grown by a hydrothermal method. The regular stacking of the rock salt slabs and the BiFeO3-like perovskite blocks along the c axis of the crystal makes the Bi4.2K0.8Fe2O9+δ nanobelts have a natural magnetoelectric–dielectric superlattice structure. The most striking result is that the bulk material made of the Bi4.2K0.8Fe2O9+δ nanobelts is of multiferroicity near room temperature accompanied with a structure anomaly. When an external magnetic field is applied, the electric polarization is greatly suppressed, and correspondingly, a large negative magnetocapacitance coefficient is observed around 270 K possibly due to the magnetoelectric coupling effect. Our result provides contributions to the development of single phase multiferroics.

Polarization enhancement and ferroelectric switching enabled by interacting magnetic structures in DyMnO3 thin films

“…Multiferroics with coexisting and intimately coupled ferroelectric (FE) and magnetic orders, have attracted considerable attentions due to their vast application potentials and fundamental interest in the past decade 1 2 3 4 5 6 . It has been confirmed that a series of magnetic configurations can break the spatial inversion symmetry and thus produce spontaneous polarization ( P ) 4 .…”

Room Temperature Exchange Bias in Structure-Modulated Single-Phase Multiferroic Materials

“…Exchange bias (EB) induced by interfacial exchange coupling of a ferromagnetic (FM) material with an adjacent antiferromagnetic (AFM) material has been extensively studied for its scientific interest and potential applications in magnetic storage, magnetic tunnel junctions, and spin-electronic devices. − Although a comprehensive understanding of EB is still frusrating researchers, a variety of artificial systems have been developed in the past decade, for example, AFM/FM film, − core–shell nanoparticles, , and other heterogeneous materials consisting of FM and AFM structures. , Unfortunately, EB for most materials exists at temperatures that are far below room temperature, which greatly hinders their potential applications as devices. , Additionally, complicated and energy-consuming techniques or processes are required to fabricate such artificial materials to combine together components with different lattice parameters and different suitable preparation temperatures. − Consequently, the availability of a single-phase EB material with promising room temperature operation would be more convenient for the realization of potential devices, either in terms of fabrication or device operation. So far, raw single-phase oxides including SmFeO 3 single crystals, Bi 4.2 K 0.8 ­Fe 2 O 9+δ nanobelts, and BiFeO 3 nanochains have been reported to show RT EB phenomena together with different function mechanisms. ,,− However, the fabrication of single crystals or nanobelts for device applications remains a big challenge, which usually inflicts a high cost and low output. Therefore, exploring effective RT EB single-phase oxides that can be easily fabricated would be extremely important not only for fundamental physics but also for future device application in spintronics and so forth.…”