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