Quantum Tunneling in Half-Integer-Spin Kagome-Lattice Langasites
  Employing the muon spin relaxation technique we evidence temperature independent magnetic fluctuations persisting down to the lowest temperatures in the samarium-based ($J=5/2$) kagome-lattice Langasite. A detailed bulk-magnetization characterization and comparison to the neodymium-based ($J=9/2$) compound allow us to assign the persistent spin dynamics to a quantum tunneling process. This is facilitated by pairwise anisotropic magnetic interactions, leading to a universal scaling of the muon relaxation. Our study reveals a remarkable analogy between weakly interacting half-integer-spin rare-earth magnets and molecular nanomagnets. 
A. Zorko, F. Bert, P. Mendels, A. Poto\v{c}nik, A. Amato, C. Baines,   K. Marty, P. Bordet, P. Lejay, E. Lhotel, V. Simonet,...
cond-mat.str-el