Impurity effects on the triangular antiferromagnets Ni1-xMxGa2S4 (M=Mn, Fe, Co and Zn) are studied. The 2D frozen spin-disordered state of NiGa2S4 is stable against the substitution of Zn2+ (S=0) and Heisenberg Fe2+ (S=2) spins, and exhibits a T2-dependent magnetic specific heat, scaled by the Weiss temperature. In contrast, the substitutions with Co2+ (S=3/2) spin with Ising-like anisotropy and Heisenberg Mn2+ (S=5/2) spin induce a conventional spin glass phase below 1 K. From these comparisons, it is suggested that the integer size of the Heisenberg spins is important to stabilize the 2D coherent behavior observed in the frozen spin-disordered state.
ASJC Scopus subject areas
- Physics and Astronomy(all)