Disappearance of Quasi-Ising Character in Triangular Lattice Antiferromagnet CuFeO₂ by a Small Amount of Substitution

Abstract

The effect of a small amount of substitution on magnetic ordering in a frustrated triangular lattice antiferromagnet CuFeO₂ has been studied by neutron diffraction, magnetic susceptibility and specific heat measurements on CuFe_1−xAl_xO₂ single-crystals with x=0.02 and x=0.05. With only a small amount of substitution, x=0.02, the zero-field successive magnetic phase transitions with quasi-Ising character observed for x=0.00 are entirely changed to successive phase transitions from a paramagnetic state to an incommensurate complex state through an incommensurate magnetic state, suggesting that the original Heisenberg spin character hidden in CuFeO₂ is retrieved.