Fullerene-based 0D ferroelectrics/multiferroics for ultrahigh-density and ultrafast nonvolatile memories

Recently, the existence of room-temperature ferroelectricity has been experimentally confirmed in a number of two-dimensional (2D) materials. With a switching barrier large enough to be stable against thermal fluctuation, ferroelectricity in even lower dimensions like 1D or 0D may be explored for data storage of higher density, which has been scarcely reported. Here, we show the first-principles design of 0D ferroelectrics/multiferroics based on polar functionalized fullerene. It turns out that the ferroelectric polarization of endohedral metallofullerenes can be reversed with the diffusion of metal ions inside when the fullerene is fixed on a substrate. If its bonding with the substrate is relatively weak, the rotation of fullerene will be more favorable in energy for ferroelectric switching. The switching barriers of both modes, for the candidates with considerable magnetic moments and dipole moments, are all in the ideal range for working under ambient conditions. Moreover, compared with conventional ferroelectrics for data storage, they may be endowed with a high areal density (∼105 Gbit per in2) and high writing speed (∼102 GHz) that are respectively more than 2 and 3 orders of magnitude higher.