Magnetic and dielectric order in the kagomelike francisite Cu3Bi(SeO3)2O2Cl

Abstract

We report a single-crystal neutron diffraction and inelastic neutron scattering study on the spin 1/2 cuprate Cu3Bi(SeO3)2O2Cl, complemented by dielectric and electric polarization measurements. The study clarifies a number of open issues concerning this complex material, whose frustrated interactions on a kagome-like lattice, combined with Dzyaloshinskii-Moriya interactions, are expected to stabilize an exotic canted antiferromagnetic order. In particular, we determine the nature of the structural transition occurring at 115 K, the magnetic structure below 25 K resolved in the updated space group, and the microscopic ingredients at the origin of this magnetic arrangement. This was achieved by an analysis of the measured gapped spin waves, which signifies the need of an unexpected and significant anisotropic exchange beyond the proposed Dzyaloshinskii-Moriya interactions. Finally, we discuss the mutliferroic properties of this material with respect to the space group symmetries.

Archetypal Soft-Mode-Driven Antipolar Transition in Francisite Cu3Bi(SeO3)2Milési-Brault1, Toulouse2, Constable3 et al. 2020Phys. Rev. Lett.24070View full textAdd to dashboardCite

“…In the second scenario, the transition is between two non-polar phases, with a doubling of the unit cell, and the soft mode is found at the zone boundary in the high-symmetry phase, so that it can no longer be followed by optical spectroscopy techniques. Crystallographic data [21] support the latter scenario, but the former has also been discussed in past spectroscopic studies [23,24]. In order to confirm whether this comes with a mode softening at the zone boundary above T c as anticipated from the structural studies, we performed inelastic X-ray scattering (IXS) to follow the mode at the Z point of the Brillouin zone (See Fig.…”

“…Neutron refinements have established a symmetry descent P mmn −→ P cmn, whereby a mirror plane is replaced with a glide plane [21], which corresponds to the most simple one-dimensional AFE transition [2]. The small but unambiguous dielectric anomaly [21] and the nearly degenerate energies of the non-polar and polar polymorphs [22] tend to confirm the AFE character of the transition. Our study is focused on its lattice dynamics at low frequencies, with the aim to elucidate its driving mechanism.…”

“…Far above and far below the transitions temperatures, however, it deviates from linearity. We attribute this deviation predominantly to the coupling of the soft-mode to other (hard) phonon modes at high frequencies, although quantum saturation [30,32] or precursor effects of the magnetic transition [21] may conceivably play a role at low temperatures. The expectation from the most simple Landau model, whereby the Landau potential is expanded up to the 4 th order in the order parameter as G(Q) = a 0 (T − T c )Q 2 /2 + bQ 4 /4, is that the ratio of the slopes ∂E 2 /∂T above and below T c equals 2.…”

Magnetism of coupled spin tetrahedra in ilinskite-type KCu5O2(SeO3)2Cl3

“…For example, J FM of −120 K was reported in CuSe 2 O 5 47 , whereas FM interactions between nearest neighbors in francisite, Cu 3 Bi(SeO 3 ) 2 O 2 Cl 31,48,49 , may also be influenced by the SeO 3 links. The Cu–O–Cu angles of the fracisite structure are, in fact, in the same range of 110–115°, where, according to our results, both FM and AFM interactions may occur depending on the presence or absence of the SeO 3 link.…”

Flux Growth of Tungsten Oxychloride Li 23 CuW 10 O 40 Cl 5

“…Recently, it has been reported that incorporation of halides into oxides can strikingly change their electronic structures and modify the physical properties [7][8] . Several novel transition-metal oxychlorides have been reported to date, such as MnSb 4 O 6 Cl 2 [9] , PbCu 2 (SeO 3 ) 2 Cl 2 [10] , Cu 3 Bi(SeO 3 ) 2 O 2 Cl [ 11 ] , FeTe 2 O 5 X (X=Cl, Br) [ 1 2 ] , SrCu 2 (SeO 3 ) 2 Cl 2 [13] , SmSb 2 O 4 Cl [14] , and MSb 2 O 3 (OH)Cl (M=Co, Fe, Mn) [15] . Above-mentioned materials show novel structures and special magnetic properties due to their diversity structural which was more helpful to generate the magnetic ordering during low temperature.…”