paper

Neutron scattering and muon-spin spectroscopy studies of the magnetic triangular-lattice compounds $A_{2}$ La $_{2}$ NiW $_{2}$ O $_{12}$ ( $A$ = Sr, Ba)

arXiv:2307.04116 · doi:10.1103/PhysRevMaterials.7.074403

Abstract

We report on the geometrically frustrated two-dimensional triangular-lattice magnets $A_{2}$ La $_{2}$ NiW $_{2}$ O $_{12}$ ( $A$ = Sr, Ba) studied mostly by means of neutron powder diffraction (NPD) and muon-spin rotation and relaxation ( $I^¼$ SR) techniques. The chemical pressure induced by the Ba-for-Sr substitution suppresses the ferromagnetic (FM) transition from 6.3 K in the Ba-compound to 4.8 K in the Sr-compound. We find that the $R 3 ˉ$ space group reproduces the NPD patterns better than the previously reported $R 3 ˉ m$ space group. Both compounds adopt the same magnetic structure with a propagation vector $k = (0, 0, 0)$ , in which the Ni $^{2 +}$ magnetic moments are aligned ferromagnetically along the $c$ -axis. The zero-field {\textmu}SR results reveal two distinct internal fields (0.31 and 0.10 T), caused by the long-range ferromagnetic order. The small transverse muon-spin relaxation rates reflect the homogeneous internal field distribution in the ordered phase and, thus, further support the simple FM arrangement of the Ni $^{2 +}$ moments. The small longitudinal muon-spin relaxation rates, in both the ferromagnetic- and paramagnetic states of A $_{2}$ La $_{2}$ NiW $_{2}$ O $_{12}$ , indicate that spin fluctuations are rather weak. Our results demonstrate that chemical pressure indeed changes the superexchange interactions in $A_{2}$ La $_{2}$ NiW $_{2}$ O $_{12}$ compounds, with the FM interactions being dominant.

8 pages, 7 figures; accepted by Phys. Rev. Materials

Neutron scattering and muon-spin spectroscopy studies of the magnetic triangular-lattice compounds A2​La2​NiW2​O12​ (A = Sr, Ba)

Abstract

Neutron scattering and muon-spin spectroscopy studies of the magnetic triangular-lattice compounds $A_{2}$ La $_{2}$ NiW $_{2}$ O $_{12}$ ( $A$ = Sr, Ba)