Evidence For Unidimensional Low-Energy Excitations As The Origin Of Persistent Spin Dynamics In Geometrically Frustrated Magnets

We report specific heat, magnetic, and muon spin relaxation measurements performed on a polycrystalline sample of the normal spinel CdHo2S4. The rare-earth ions sit on a lattice of corner-sharing regular tetrahedra as in pyrochlore compounds. Magnetic ordering is detected at T-c similar or equal to 0.87 K. From spin-lattice relaxation rate measurements on both sides of T-c we uncover similar magnetic excitation modes driving the so-called persistent spin dynamics at T < T-c. Unidimensional excitations are argued to be at its origin. Often observed spin loop structures are suggested to support these excitations. The possibility of a generic mechanism for their existence is discussed.