Impurity Effect on the Stability of the Ground-State Spin Configuration in Triangular Lattice Antiferromagnet CuFeO₂

Abstract

Effect of impurities on the high-field magnetization process in a frustrated antiferromagnet CuFeO₂ is studied for powder samples of CuFe_1-xAl_xO₂ (0≤ x≤ 0.1) and CuFe_1-xCr_xO₂ (0≤ x≤ 0.08) using a pulse magnet up to 38, T. For the pure Fe compound distinct magnetization anomalies are successively observed at 7, 12 and 20, T due to the field-induced transitions originated from a subtle balance of competing interactions. These anomalies rapidly disappear with increasing impurity concentration. The effect of impurities is interpreted in terms of the magnetic domain model in which the collinear spin structure of the pure system survives locally as domains without coherence as a consequence of partial suppression of a geometrical frustration by impurities.