Neutron scattering and muon-spin spectroscopy studies of the magnetic triangular-lattice compounds A₂La₂NiW₂ O₁₂ (A=Sr,Ba)
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2023-07
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Journal Article
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Abstract
We report on the geometrically frustrated two-dimensional triangular-lattice magnets A₂La₂NiW₂ O₁₂ (A=Sr,Ba) studied mostly by means of neutron powder diffraction (NPD) and muon-spin rotation and relaxation (μSR) 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 R3¯ space group reproduces the NPD patterns better than the previously reported R3¯m space group. Both compounds adopt the same magnetic structure with a propagation vector k=(0,0,0), in which the Ni2+ magnetic moments are aligned ferromagnetically along the c axis. The zero-field μSR results reveal two distinct internal fields (0.31 and 0.10 T), caused by the long-range FM 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 Ni2+ moments. The small longitudinal muon-spin relaxation rates, in both the ferromagnetic and paramagnetic states of A₂La₂NiW₂ O₁₂ indicate that spin fluctuations are rather weak. Our results demonstrate that chemical pressure indeed changes the superexchange interactions in A₂La₂NiW₂ O₁₂ compounds, with the FM interactions being dominant.
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published
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Volume
7 (7)
Pages / Article No.
74403
Publisher
American Physical Society