Giant Thermal Enhancement of the Electric Polarization in Ferrimagnetic BiFe${}_{1-x}$Co${}_x$O${}_3$ Solid Solutions Near Room Temperature

Abstract

Thermal excitations typically reduce the electric polarization in ferroelectric materials. Here, we show by means of first-principles calculations that multiferroic BiFe${}_{1-x}$Co${}_x$O${}_3$ solid solutions with $0.25\le x\le 0.50$ (BFCO) represent a noteworthy exception to this behaviour. In particular, we find that at room temperature and for moderate pressures of $0.1$-$1.0$ GPa, depending on the composition, the electric polarization of bulk BFCO increases by $\sim 200$%. The origin of such an exceptional behavior is a phase transformation involving a low-$T$ rhombohedral ($\mathcal{R}$) phase and a high-$T$ super-tetragonal ($\mathcal{T}$) phase. Both $\mathcal{R}$ and $\mathcal{T}$ phases are ferrimagnetic near room temperature with an approximate net magnetization of $0.13$${\mu }_B$ per formula unit. Contrarily to what occurs in either bulk BiFeO${}_3$ or BiCoO${}_3$, the $\mathcal{T}$ phase is stabilized over the $\mathcal{R}$ by increasing temperature due to its higher vibrational entropy. This extraordinary $T$-induced $\mathcal{R}\to \mathcal{T}$ phase transition is originated by polar phonon modes involving concerted displacements of transition-metal and oxygen ions.

6 pages, 4 figures

References in corpus (6)

• Restoring the density-gradient expansion for exchange in solids and surfaces
• Generalized gradient approximation for solids and their surfaces
• Structure and spin dynamics of multiferroric BiFeO${}_3$
• Giant Negative Thermal Expansion Induced by the Synergistic Effects of Ferroelectrostriction and Spin-Crossover in PbTiO3-Based Perovskites
• Prediction of large barocaloric effects in thermoelectric superionic materials
• Giant Direct and Inverse Electrocaloric Effects in Multiferroic Thin Films

Cited by in corpus (3)

• Manipulation of magnetic domain wall by ferroelectric switching: Dynamic magnetoelectricity at the nanoscale
• Lead-free room-temperature ferroelectric thermal conductivity switch using anisotropies in thermal conductivities
• Colossal room-temperature electrocaloric strength aided by hydrostatic pressure in lead-free multiferroic solid solutions