Spin- 12 chains with alternating antiferromagnetic (AF) and ferromagnetic (FM) couplings exhibit quantum entanglement as the integer-spin Haldane chains and might be similarly utilized for quantum ...computations. Such alternating AF-FM chains have been proposed to be realized in the distorted honeycomb lattice compound Na2Cu2TeO6 , but to confirm this picture a comprehensive understanding of the exchange interactions including terms outside of the idealized model is required. Here, we employ neutron scattering to study the spin dynamics in Na2Cu2TeO6 and accurately determine the coupling strengths through the random phase approximation and density functional theory approaches. We find the AF and FM intrachain couplings are the dominant terms in the spin Hamiltonian, while the interchain couplings are AF but perturbative. This hierarchy in the coupling strengths and the alternating signs of the intrachain couplings can be understood through their different exchange paths. Our results establish Na2Cu2TeO6 as a weakly coupled alternating AF-FM chain compound and reveal the robustness of the gapped ground state in alternating chains under weak interchain couplings.
Co-substituted Ni1-xCoxBr2 (0≤x≤1) single crystals were synthesized using vapor transport. As a result, the physical properties of the crystals were characterized by x-ray powder diffraction, ...magnetization, and specific-heat measurements. Room-temperature x-ray powder diffraction data indicate that a change from the CdCl2 structure type to the CdI2 structure type occurs within 0.56<x<0.76. NiBr2 has a commensurate antiferromagnetic phase below TN ≈ 46 K and an incommensurate magnetic ground state below TIC ≈ 20 K. Both magnetic transitions are affected by cobalt substitution, and the incommensurate phase transition is present up to at least x=0.56. Here, the evolution of magnetism has been studied as a function of cobalt content and is summarized in the temperature-composition phase diagram.
Single crystals of Ln{sub 2}Ru{sub 3}Al{sub 15+x} (Ln=Gd, Tb) have been grown using the self-flux method under Ru-poor conditions. The structure of the Gd analog is found to be highly dependent on ...the synthesis method. Gd{sub 2}Ru{sub 3}Al{sub 15.08} orders antiferromagnetically at 17.5 K. Tb{sub 2}Ru{sub 3}Al{sub 15.05} enters an antiferromagnetic state at 16.6 K followed by a likely incommensurate-to-commensurate transition at 14.9 K for crystals oriented with H//ab. For crystals oriented with H//c, a broad maximum is observed in the temperature dependent M/H, indicative of a highly anisotropic magnetic system with the hard axis in the c-direction. The magnetization as a function of field and magnetoresistance along the ab-direction of Tb{sub 2}Ru{sub 3}Al{sub 15.05} display a stepwise behavior and indicate strong crystalline electric field effects. - Graphical abstract: Single crystal, structure, and highly anisotropic magnetoresistance due to strong crystalline electric field effects of Tb{sub 2}Ru{sub 3}Al{sub 15.05}. - Highlights: • Single crystals of Ln{sub 2}Ru{sub 3}Al{sub 15+x} were grown for the first time via flux growth. • The structure of Gd{sub 2}Ru{sub 3}Al{sub 15.09} differs from that of arc melted Gd{sub 2}Ru{sub 3.08}Al{sub 15}. • Tb{sub 2}Ru{sub 3}Al{sub 15.05} exhibits highly anisotropic magnetic and transport properties. • The properties of Tb{sub 2}Ru{sub 3}Al{sub 15.05} arise due to crystalline electric field effects.
Single crystals of Ln2Ru3Al15+x (Ln=Gd, Tb) have been grown using the self-flux method under Ru-poor conditions. The structure of the Gd analog is found to be highly dependent on the synthesis ...method. Gd2Ru3Al15.08 orders antiferromagnetically at 17.5K. Tb2Ru3Al15.05 enters an antiferromagnetic state at 16.6K followed by a likely incommensurate-to-commensurate transition at 14.9K for crystals oriented with H//ab. For crystals oriented with H//c, a broad maximum is observed in the temperature dependent M/H, indicative of a highly anisotropic magnetic system with the hard axis in the c-direction. The magnetization as a function of field and magnetoresistance along the ab-direction of Tb2Ru3Al15.05 display a stepwise behavior and indicate strong crystalline electric field effects.
Single crystal, structure, and highly anisotropic magnetoresistance due to strong crystalline electric field effects of Tb2Ru3Al15.05.
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•Single crystals of Ln2Ru3Al15+x were grown for the first time via flux growth.•The structure of Gd2Ru3Al15.09 differs from that of arc melted Gd2Ru3.08Al15.•Tb2Ru3Al15.05 exhibits highly anisotropic magnetic and transport properties.•The properties of Tb2Ru3Al15.05 arise due to crystalline electric field effects.
For this work, single crystals were grown and characterized to investigate the physical properties and magnetic ground state of BaNd2PtO5, a candidate to host physics of the Shastry-Sutherland model. ...Analysis of single crystal x-ray diffraction data yields an updated crystal structure, similar to the prior report but now in space group P4/mbm. Magnetization and specific heat measurements reveal an antiferromagnetic transition at TN=1.9K and a large magnetic anisotropy with in-plane magnetization much larger than out-of-plane magnetization. Single crystal neutron diffraction at zero field reveals a propagation vector of ($\frac{1}{2}$$\frac{1}{2}$$\frac{1}{2}$) for the magnetic ground state as compared to the ($\frac{1}{2}$$\frac{1}{2}$0) wave vector observed in the related body-centered material BaNd2ZnO5. The ground state is found to be a fully compensated antiferromagnet with diffraction data well fitted within the magnetic space group PS–1 (BNS setting #2.7). The ordered moment is mostly in the basal plane with nearest neighbors forming ferromagnetic dimers, however it also has a finite out-of-plane component unlike the related easy-plane materials BaNd2ZnO5 and BaNd2ZnS5. Field-induced transitions are observed below TN when the field is applied within the basal plane, and in-plane anisotropy of the associated critical fields is observed. The magnetization is strongly impacted by misalignment of the field away from high symmetry directions. These results suggest complex magnetic structures may arise in the field-induced states, and they highlight the need for extreme care when studying this and related Shastry-Sutherland materials.
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