Raman scattering of 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> mixed-dimensionality antiferromagnetic <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>α</mml:mi><mml:mtext>−</mml:mtext><mml:msub><mml:mi>Cu</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">V</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>7</mml:mn></mml:msub></mml:mrow></mml:math>
Hemant Singh Kunwar, Isha, Arvind Yogi, Binoy Krishna De, Vivek Dwij, Mayanak K. Gupta, R. Mittal, R. Venkatesh, R. J. Chaudhary, Mahesh Vedpathak, Vasant Sathe
Abstract
We present a detailed investigation of the lattice vibrations and magnetic properties of the spin-$\frac{1}{2}\phantom{\rule{4pt}{0ex}}\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{Cu}}_{2}{\mathrm{V}}_{2}{\mathrm{O}}_{7}$ system by means of x-ray diffraction (XRD), magnetic susceptibility, specific heat, x-ray absorption spectroscopy (XAS), x-ray photoelectron spectroscopy (XPS), and Raman scattering measurements along with a phonon structure calculations by density-functional theory (DFT). Thermodynamic measurements show a long-range ordered (LRO) state at N\'eel temperature $T{}_{N}\ensuremath{\sim}33.4$ K. From the molar susceptibility curves analysis an effective magnetic moment of 1.83 ${\ensuremath{\mu}}_{B}$ and an antiferromagnetic intrachain exchange coupling of $\ensuremath{\sim}62.13$ K ($\ensuremath{\sim}5.35$ meV) is deduced. Despite exchange coupling in 1D chains, the susceptibility, low-temperature heat-capacity, and Raman spectroscopic analysis confirms that the antiferromagnetic order emerges from the mixed dimensionality nature of the exchange couplings and interchain exchange coupling was found to be $\ensuremath{\sim}16.91$ K. Temperature-dependent Raman spectra has been performed in the temperature range 3.5 K to 300 K and established the spin-lattice coupling below 50 K, which appears well above ${T}_{N}$ and is attributed to short-range magnetic ordering (${T}_{SRO}$). The spin-lattice coupling constant has been calculated for various modes. Further, the detailed study of lattice dynamics by first-principle calculations on $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{Cu}}_{2}{\mathrm{V}}_{2}{\mathrm{O}}_{7}$ is presented.