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arXiv · 1401.3400

Characterization of the Spin-1/2 Linear-Chain Ferromagnet CuAs$_2$O$_4$

K. Caslin·R. K. Kremer·F. S. Razavi·A. Schulz·A. Muñoz·F. Pertlik·J. Liu·M. -H. Whangbo·J. M. Law
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Abstract

The magnetic and lattice properties of the $S$=1/2 quantum-spin-chain ferromagnet, CuAs$_2$O$_4$, mineral name trippkeite, were investigated. The crystal structure of CuAs$_2$O$_4$ is characterized by the presence of corrugated CuO$_2$ ribbon chains. Measurements of the magnetic susceptibility, heat capacity, electron paramagnetic resonance and Raman spectroscopy were performed. Our experiments conclusively show that a ferromagnetic transition occurs at $\sim$7.4 K. $\textit{Ab initio}$ DFT calculations reveal dominant ferromagnetic nearest-neighbor and weaker antiferromagnetic next- nearest-neighbor spin exchange interactions along the ribbon chains. The ratio of $J_{\rm nn}$/$J_{\rm nnn}$ is near -4, placing CuAs$_2$O$_4$ in close proximity to a quantum critical point in the $J_{\rm nn}$ - $J_{\rm nnn}$ phase diagram. TMRG simulations used to analyze the magnetic susceptibility confirm this ratio. Single-crystal magnetization measurements indicate that a magnetic anisotropy forces the Cu$^{2+}$ spins to lie in an easy plane perpendicular to the $c$-axis. An analysis of the field and temperature dependent magnetization by modified Arrott plots reveals a 3d-XY critical behavior. Lattice perturbations induced by quasi-hydrostatic pressure and temperature were mapped via magnetization and Raman spectroscopy.

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K. Caslin, R. K. Kremer, F. S. Razavi, A. Schulz, A. Muñoz, F. Pertlik, J. Liu, M. -H. Whangbo, J. M. Law. 2014-01-15. Characterization of the Spin-1/2 Linear-Chain Ferromagnet CuAs$_2$O$_4$. https://doi.org/10.1103/physrevb.89.014412

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