Phase diagram and magnetic structures of the Co-bearing dugganites Pb₃TeCo₃A₂O₁₄(A = V, P)

Abstract

Exhibiting rich magnetic behaviour and potentially multiferroic properties, the dugganites, a Te(6+) containing subgroup of the langasite series, are an attractive family of compounds for future study. It was recently shown that Pb-bearing members of the dugganite series undergo distortions away from the P321 symmetry that is characteristic of the langasites. Here, we detail the consequences these distortions have on the magnetism exhibited by Pb3TeCo3V2O14 and Pb3TeCo3P2O14, solving the magnetic structures of both compounds with respect to a new supercell. Using neutron scattering and magnetic susceptibility measurements, we show that small applied magnetic fields can seriously perturb the delicate magnetic states in both of these systems. This is further demonstrated by presenting how doping P(5+) onto the nonmagnetic V(5+) site completely changes the magnetic structure from either of the end series members. Finally, it is shown using inelastic neutron scattering and magnetic susceptibility measurements that Pb3TeCo3V2O14 can be characterized using a model for isosceles trimers, which do not exist in the previously reported P321 subcell.

Magnetic phase diagram and first-principles study ofPb3TeCo3V2O14

“…Together with ferromagnetic J c and J 2 they relieve frustration and make Co ions neighboring in the c direction to be antiferromagnetically ordered, which agrees with experimental findings. 5,6 We repeated calculation of the exchange constants with slightly smaller U eff and found that with decrease of U eff on 0.5 eV both J d1 + J d2 and J 2 increase in absolute values as expected for superexchange (J d1 + J d2 = 5.3 K, J 2 = -2.0 K), while J 1 and J c practically do not change (J 1 = 0.1 K, J c = 2.6 K).…”

“…P121) and multiplicated cell parameters. [4][5][6] The presence of magnetic Co 2+ and Mn 2+ ions in the structure add new, magnetic dimension to langasite's. Magnetic properties in these compounds are related to such substitutions since another transition metal in the structure, vanadium, is pentavalent and do not carry magnetic moment.…”

“…Recently, the magnetic and structural properties of Pb 3 TeCo 3 V 2 O 14 were the subject of intense studies. [4][5][6] It was assumed initially, that this compound crystallizes in trigonal unit cell with noncentrosymmetric P321 space group, similar to langasite. At lowering temperature, Pb 3 TeCo 3 V 2 O 14 orders magnetically in two steps at T N1 ~ 9 K and T N2 ~ 6 K. Both these transitions are reflected in dielectric permittivity signaling the coupling of magnetic and electric subsystems.…”

“…5 Finally, precise X-ray diffraction and neutron scattering measurements were carried out resulting in new magnetic structure solutions with propagation vectors q 1 = (½, 0, -½) at T N2 < T < T N1 and q 2 = (½,½, -½) at T < T N2 . 6 It was shown, that the low temperature magnetic structure of every Te-containing member of the langasite family, i.e. ions are arranged in zig-zag manner within channels of magnetically passive layers.…”

Nuclear and magnetic supercells in the multiferroic candidate: Pb3TeMn3P2O14

“…Recently, a Te 6 þ -containing subgroup of the langasites, called the dugganites after the natural mineral Pb 3 TeZn 3 As 2 O 14 [6], has been receiving interest [24][25][26][27][28][29][30]. Te 6 þ allows one to substitute divalent 3d metal ions into the trimer site due to charge balancing and preferential symmetry constraints.…”