Structural and physical properties of CaFe4As3

Abstract

We report the synthesis and structural and physical properties of CaFe${}_{4}$As${}_{3}$ single crystals. Needle-like single crystals of CaFe${}_{4}$As${}_{3}$ were grown out of Sn flux and the compound adopted an orthorhombic structure as determined by x-ray diffraction measurements. Electrical, magnetic, and thermal properties indicate that the system undergoes two successive phase transitions, occurring at ${T}_{N1}\ensuremath{\sim}90$ K and ${T}_{N2}\ensuremath{\sim}26$ K. At ${T}_{N1}$, electrical resistivities (${\ensuremath{\rho}}_{b}$ and ${\ensuremath{\rho}}_{ac}$) are enhanced while magnetic susceptibilities (${\ensuremath{\chi}}_{b}$ and ${\ensuremath{\chi}}_{ac}$) are reduced in both directions, parallel and perpendicular to the $b$ axis, consistent with the scenario of antiferromagnetic spin-density-wave formation. At ${T}_{N2}$, specific heat reveals a slope change, and ${\ensuremath{\chi}}_{ac}$ decreases sharply but ${\ensuremath{\chi}}_{b}$ shows a clear jump before it decreases again with decreasing temperature. Remarkably, both ${\ensuremath{\rho}}_{b}$ and ${\ensuremath{\rho}}_{ac}$ decrease sharply with thermal hysteresis, indicating the first-order nature of the phase transition at ${T}_{N2}$. At low temperatures, ${\ensuremath{\rho}}_{b}$ and ${\ensuremath{\rho}}_{ac}$ can be described by $\ensuremath{\rho}={\ensuremath{\rho}}_{0}+{AT}^{\ensuremath{\alpha}}$ (${\ensuremath{\rho}}_{0}$, $A$, and $\ensuremath{\alpha}$ are constants). Interestingly, these constants vary with applied magnetic field. The ground state of CaFe${}_{4}$As${}_{3}$ is discussed.