Magnetic Frustration on a Kagomé Lattice in R$_{3}$Ga$_{5}$SiO$_{14}$ Langasites with R = Nd, Pr

摘要: In the R$_{3}$Ga$_{5}$SiO$_{14}$ compounds, network R of rare earth cations form well separated planes corner sharing triangles topologically equivalent to a kagome lattice. Powder samples and single crystals with = Nd Pr were prepared magnetostatic measurements performed under magnetic field up 10 T in temperature range from 1.6 K 400 K. Analysis susceptibility at high temperatures where only quadrupolar term crystal electric prevails, suggests that moments can be modeled as coplanar elliptic rotators perpendicular three fold axis structure interact antiferromagnetically. Nonetheless, disordered phase ascribed geometric frustration persists down lowest which is about 25 times smaller than energy scale for exchange interactions.