Quasi-one-dimensional magnetism in the spin-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mfrac><mml:mn>1</mml:mn><mml:mn>2</mml:mn></mml:mfrac></mml:math> antiferromagnet <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>BaNa</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mi>Cu</mml:mi><mml:msub><mml:mrow><mml:mo>(</mml:mo><mml:msub><mml:mi>VO</mml:mi><mml:mn>4</mml:mn></mml:msub><mml:mo>)</mml:mo></mml:mrow><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>
Sebin J. Sebastian, K. Somesh, M. Nandi, N. Ahmed, Pallab Bag, M. Baenitz, Bonho Koo, J. Sichelschmidt, Alexander A. Tsirlin, Yuji Furukawa, R. Nath
Abstract
We report synthesis and magnetic properties of quasi-one-dimensional spin-$\frac{1}{2}$ Heisenberg antiferromagnetic chain compound ${\mathrm{BaNa}}_{2}\mathrm{Cu}{({\mathrm{VO}}_{4})}_{2}$. This orthovanadate has a centrosymmetric crystal structure, $C2/c$, where the magnetic ${\mathrm{Cu}}^{2+}$ ions form spin chains. These chains are arranged in layers, with the chain direction changing by ${62}^{\ensuremath{\circ}}$ between the two successive layers. Alternatively, the spin lattice can be viewed as anisotropic triangular layers upon taking the interchain interactions into consideration. Despite this potential structural complexity, temperature-dependent magnetic susceptibility, heat capacity, electron spin resonance intensity, and nuclear magnetic resonance (NMR) shift agree well with the uniform spin-$1/2$ Heisenberg chain model with an intrachain coupling of $J/{k}_{\mathrm{B}}\ensuremath{\simeq}5.6$ K. The saturation field obtained from the magnetic isotherm measurement consistently reproduces the value of $J/{k}_{\mathrm{B}}$. Further, the $^{51}\mathrm{V}$ NMR spin-lattice relaxation rate mimics the one-dimensional character in the intermediate temperature range, whereas magnetic long-range order sets in below ${T}_{\mathrm{N}}\ensuremath{\simeq}0.25$ K. The effective interchain coupling is estimated to be ${J}_{\ensuremath{\perp}}/{k}_{\mathrm{B}}\ensuremath{\simeq}0.1$ K. The theoretical estimation of exchange couplings using band-structure calculations reciprocate our experimental findings and unambiguously establish the one-dimensional character of the compound. Finally, the spin lattice of ${\mathrm{BaNa}}_{2}\mathrm{Cu}{({\mathrm{VO}}_{4})}_{2}$ is compared with the chemically similar but not isostructural compound ${\mathrm{BaAg}}_{2}\mathrm{Cu}{({\mathrm{VO}}_{4})}_{2}$.