Colloquia

In geometrically frustrated magnets (GFMs), the incompatibility between the interactions of the magnetic degrees of freedom in a lattice and the underling crystal geometry leads to the frustration. The massive level of degeneracy introduced by this frustration can persist to low temperatures to enhance the spin fluctuations and suppress the magnetic ordering, therefore resulting exotic spin ground states with abnormal thermo-dynamics. In this talk, two GFMs will be introduced: (i) Spin ice with pyrochlore structure, in which the ground state is a short range ordering of the “two spin in two spin out” configurations on tetrahedrons following the “ice rule”; (ii) Quantum spin liquid (QSL), in which the strong quantum fluctuations of the spins with small number (S = 1/2 and 1) destroy the magnetic ordering and lead to a spin-liquid like ground state. Following the introduction, we present our recently studies on new pyrochlore materials Pr₂Sn₂O₇ and Dy₂Ge₂O₇, and new QSL materials Ba₃CuSb₂O₉ and Ba₃NiSb₂O₉ with a triangular lattice of S = 1/2 and S = 1, respectively.