“…The first ferroelectric crystal, Rochelle salt, which was discovered in 1920 [2], is an organic ferroelectric material containing organic tartrate ion. At present, the study of ferroelectricity in organic solids has been limited to some well-known polymer ferroelectrics [3] like polyvinylidene difluoride (PVDF) [4][5][6][7][8][9][10], or a few low-molecular-mass compounds like thiourea [11], tetrathiafulvalene (TTF) complexes with p-bromanil (tetrabromo-p-benzoquinone) [12] and pchloranil (tetrachloro-p-benzoquinone) [13], croconic acid [14] and so on. Multiferroicity, i.e., coexistence of magnetism and ferroelectricity, is even more desirable for constructing multifunctional devices [15,16] where electrical polarization can be controlled by applied magnetic fields and magnetization by applied voltage.…”