Anisotropic magnetic property of single crystals $R$V$_6$Sn$_6$ ($R$ = Y, Gd - Tm, Lu)

Abstract

RV6Sn6 (R = Y, Gd -Tm, Lu) single crystals are synthesized by Sn-flux method and their physical properties are characterized by magnetization, resistivity, and specific heat measurements. Powder X-ray diffraction patterns of all samples can be well indexed with the hexagonal HfFe6Ge6type structure, where rare-earth atoms form hexagonal layers and vanadium atoms form Kagome layers. At high temperatures, magnetic susceptibility measurements of moment bearing rare-earths (R = Gd -Tm) follow Curie-Weiss behavior. Effective moments estimated from the polycrystalline average of magnetic susceptibility curves are consistent with the values for free R 3+ ion. Strong magnetic anisotropy due to crystalline electric field effects is observed for moment bearing rareearths, except GdV6Sn6. The easy magnetization direction is determined to be c-axis for R = Tb -Ho and ab-plane for R = Er, and Tm. The vanadium ions in RV6Sn6 possess no magnetic moment. The compounds for R = Y and Lu exhibit typical characteristics of paramagnetic metals. At low temperatures, the magnetic ordering is confirmed from magnetization, specific heat, and resistivity: the highest TN = 4.9 K for GdV6Sn6 and the lowest TN = 2.3 K for HoV6Sn6. No magnetic ordering is observed down to 1.8 K for R = Er and Tm. A slight deviation of the magnetic ordering temperature from the de Gennes scaling suggests the dominant Ruderman-Kittel-Kasuya-Yosida (RKKY) exchange interaction between rare-earth moments in metallic RV6Sn6 compounds.