Magneto-crystalline anisotropy in R2PdSi3 (R=Tb, Dy, Ho, Er, Tm) single crystals

We present single crystal AC-susceptibility and magnetisation measurements of R2PdSi3 compounds with R=Tb, Dy, Ho, Er, and Tm. The crystal-electric field (CEF) parameter B20 and the value of the two-ion interaction exchange integral J(Q=0)J(Q=0) are evaluated from the anisotropy of the AC-susceptibility measurements in the paramagnetic state. In addition, the magnetic anisotropy is investigated by magnetisation measurements well below the magnetic ordering temperature. Our results yield the first parameter in the CEF Hamiltonian B20/(α〈r2〉) to be around −40 meV/Å2 for R2PdSi3. The influence of higher order terms in the CEF Hamiltonian results in a crossing of magnetic hard and easy directions in the paramagnetic state for Dy2PdSi3 and Ho2PdSi3. The anisotropy due to the CEF is conserved in the ordered state. The observed magnetic properties turn out to be complex due to the delicate interplay of CEF effects and magnetic two-ion interactions.