Anisotropic magnetization studies of R2 Co Ga8 (R = Gd, Tb, Dy, Ho, Er, Tm, Y and Lu) single crystals
Abstract
Single crystals of R2CoGa8 series of compounds were grown, for the first time, by high temperature solution growth (flux) method. These compounds crystallize in a tetragonal crystal structure with the space group P4/mmm. It has been found that R2CoGa8 phase forms only with the heavier rare earths, starting from Gd with a relatively large c/a ratio of ≈ 2.6. The resultant anisotropic magnetic properties of the compounds were investigated along the two principal crystallographic directions of the crystal viz., along [100] and [001]. The nonmagnetic compounds Y2CoGa8 and Lu2CoGa8 show diamagnetic behavior down to the lowest temperature (1.8 K) pointing out the non-magnetic nature of Co in these compounds and a relatively low density of electronic states at the Fermi level. Compounds with the magnetic rare earths order antiferromagnetically at temperatures lower than 30 K. The easy axis of magnetization for R2CoGa8 (R = Tb, Dy and Ho) is found to be along the [001] direction and it changes to [100] direction for Er2CoGa8 and Tm2CoGa8. The magnetization behavior is analyzed on the basis of crystalline electric field (CEF) model. The estimated crystal field parameters explains the magnetocrystalline anisotropy in this series of compounds.