title: Coexistence of ferroelectricity and ferromagnetism in tantalum clusters.
abstract: The atomic and electronic structures of Ta(N) (N=2-23) clusters have been determined in the framework of pseudopotential density-functional calculations, based upon an unbiased global search with guided simulated annealing to an empirical potential. It is found that the ground-state structures of Ta(N) are very similar to those of Nb(N), showing no preference for the icosahedral growth. Also, a size- and structure-dependent ferroelectricity is found in these tantalum clusters. More importantly, it is found that the ferroelectricity and ferromagnetism can coexist in the homogeneous transition-metal cluster, offering a possibility to obtain a new type of "multiferroic" materials composed of the clusters. Finally, the far-infrared spectroscopy is suggested to be an efficient tool to distinguish the ferroelectric clusters.
authors.affiliation: Group of Computational Condensed Matter Physics, National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China. wfa@nju.edu.cn
authors.forename: Wei
authors.initials: W
authors.lastname: Fa
authors.forename: Chuanfu
authors.initials: C
authors.lastname: Luo
authors.forename: Jinming
authors.initials: J
authors.lastname: Dong