Direct Magnetization-Polarization Coupling in BaCuF4

Abstract

Herewith, first-principles calculations based on density functional theory are used to describe the ideal magnetization reversal through polarization switching in BaCuF_{4} which, according to our results, could be accomplished close to room temperature. We also show that this ideal coupling is driven by a single soft mode that combines both polarization, and octahedral rotation. The later being directly coupled to the weak ferromagnetism of BaCuF_{4}. This, added to its strong Jahn-Teller distortion and its orbital ordering, makes this material a very appealing prototype for crystals in the ABX_{4} family for multifunctional applications. The described mechanism behaves ideally as it couples the ferroelectric and the magnetic properties naturally and it has not been reported previously.

Theoretical study of the magnetic properties of BaNiF$$_4$$

“…It is interesting to remark that these results were obtained considering Heisenberg interactions and single-ion anisotropy terms only while similar results were obtained by Ederer et al [23] for the BaNiF 4 compound and A. C. Garcia-Castro et al [20] for the BaCuF 4 system using an alternative description with effective single ion anisotropy contributions and a Dzyaloshinskii-Moriya interaction.…”

“…This canting produces an additional weak antiferromagnetism in the (a, c) plane. More recently, A. C. Garcia-Castro et al [20] showed that the same canting of the magnetic moments, due to an effective DM interaction coupled to the polar character of the system, also takes place in the BaCuF 4 compound. It results in the possibility to reverse, in both systems, this canting order parameter using an electric field [24].…”

“…The leading magnetic interactions in the magnetic members of the family (Mn, Fe, Co, Ni, Cu) are antiferromagnetic (AFM). Long range AFM order appears below 26.4 K for the BaMnF 4 compound [15], 54.2 K for BaFeF 4 [16], 69.6 K for BaCoF 4 [17], and 68.4 K for BaNiF 4 [18] while BaCuF 4 shows one-dimensional AFM behavior with no ex-perimental evidence of long-range ordering [19] despite some authors claiming a Néel temperature of 275 K [20].…”

Single-phase multiferroics: new materials, phenomena, and physics

“…The final class of type-I multiferroics, which was discovered long ago but recently addressed once more, is fluorides, BaMF 4 (M = Mn, Ni, Co, Fe, Cu) [ 39–41 ]. The ferroelectricity is believed to originate from the collective rotation of MF 6 octahedra, and transition metals provide magnetism.…”

Magneto-electric multiferroics: designing new materials from first-principles calculations

“…reported that a solution to this problem is to entangle octahedra rotations and ferroelectric polarization in a single soft phonon mode 161 . They reported such a possibility in BaCuF4, which is polar directly below its melting temperature (1000 K) and is a canted antiferromagnetic below its Néel temperature (TN=275 K) with weak ferromagnetism, thus making BaCuF4 multiferroic.…”