Selective Substitution of Cr in CaFe4As3 and Its Effect on the Spin Density Wave

Abstract

Single crystals of CaCr0.84Fe3.16As3, a Cr substituted analog of CaFe4As3, were grown from Sn flux and characterized with single crystal neutron diffraction. CaCr0.84Fe3.16As3 crystallizes in the orthorhombic space group Pnma with a three-dimensional framework, where Fe, Cr, and As form a covalent channel-like network with Ca2+ cations residing in the channels. CaCr0.84Fe3.16As3 has a unit cell of a = 12.057(4) A, b = 3.7374(13) A, and c = 11.694(3) A, as determined by room temperature single crystal neutron diffraction (R1 = 0.0747, wR2 = 0.1825). Structural data was also collected at 10 K. The single crystal neutron data showed that Cr selectively occupies a particular metal site, Fe(4). The antiferromagnetic transition associated with spin density wave (SDW) in the parent compound is preserved and shifts from 96 to 103 K with the selective Cr doping. Mossbauer, magnetic, and electrical resistivity measurements are reported.