Disappearance of quasi-Ising character in triangular lattice antiferromagnet CuFeO2 by a small amount of substitution

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 CuFe1-xAlxO2 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.