Crystal growth and magnetic properties of spin-$1/2$ distorted triangular lattice antiferromagnet CuLa${}_2$Ge${}_2$O${}_8$

Abstract

CuLa${}_2$Ge${}_2$O${}_8$ forms a distorted triangular lattice of quantum spin-1/2 Cu${}^{2+}$ ions. A crystal growth method was developed using the traveling-solvent floating zone technique resulting in the synthesis of a large single crystal (4 mm$\times$4 mm$\times$10 mm). The crystal was characterized with regard to phase purity and crystallinity using powder X-ray diffraction, energy dispersive X-ray analysis and Laue diffraction, and found to be of excellent quality. The magnetic properties were characterized using dc-susceptibility, magnetization, and heat capacity measurements which revealed weak magnetic frustration with long-range magnetic order occurring below $T_N=1.14(1)$~K. The magnetic structure determined using neutron powder diffraction is a commensurate, noncollinear antiferromagnetic, different from the 120${}^{\circ }$ order of an equilateral triangular antiferromagnet. The ordered moments lie in the {\bf bc}-plane, with components $m_b=0.50(3)$~${\mu }_B$ and $m_c=0.73(5)$~${\mu }_B$ along the {\bf b}- and {\bf c}-axes respectively, giving a total ordered moment of $M_{total}$= 0.89(6)${\mu }_B/$Cu${}^{2+}$ at 20~mK.

11 pages, 13 figures