[Abstract] Multiferroics, defined for those multifunctional materials in which two or more kinds of fundamental ferroicities coexist, have become one of the hottest topics of condensed matter physics and materials science in recent years. The coexistence of several order parameters in multiferroics brings out novel physical phenomena and offers possibilities for new device functions. The revival of research activities on multiferroics is evidenced by some novel discoveries and concepts, both experimentally and theoretically. In this review article, we outline some of the progressive milestones in this stimulating field, specially for those single phase multiferroics where magnetism and ferroelectricity coexist. Firstly, we will highlight the physical concepts of multiferroicity and the current challenges to integrate the magnetism and ferroelectricity into a single-phase system. Subsequently, we will summarize various strategies used to combine the two types of orders. Special attentions to three novel a) E-mail: liujm@nju.edu.cn b) E-mail: renzh@bc.edu Multiferroics 2 mechanisms for multiferroicity generation: (1) the ferroelectricity induced by the spin orders such as spiral and E-phase antiferromagnetic spin orders, which break the spatial inversion symmetry, (2) the ferroelectricity originating from the charge ordered states, and (3) the ferrotoroidic system, will be paid. Then, we will address the elementary excitations such as electromagnons, and application potentials of multiferroics. Finally, open questions and opportunities will be prospected.

We have synthesized a new layered BiS2-based compound SrFBiS2. This compound has similar structure to BiS2. It is built up by stacking up SrF layers and NaCl-type BiS2 layers alternatively along the c axis. Electric transport measurement indicates that SrFBiS2 is a semiconductor. Thermal transport measurement shows that SrFBiS2 has a small thermal conductivity and large Seebeck coefficient. First principle calculations are in agreement with experimental results and show that SrFBiS2 is very similar to LaOBiS2 which becomes superconductor with F doping. Therefore, SrFBiS2 may be a parent compound of new superconductors.