We have prepared the complete delafossite solid solution series between
diamagnetic CuAlO2 and the t2g^3 frustrated antiferromagnet CuCrO2. The
evolution with composition x in CuAl(1-x)Cr(x)O2 of the crystal structure and
magnetic properties has been studied and is reported here. The room-temperature
unit cell parameters follow the Vegard law and increase with x as expected. The
effective moment is equal to the Cr^3+ spin-only S = 3/2 value throughout the
entire solid solution. Theta is negative, indicating that the dominant
interactions are antiferromagnetic, and its magnitude increases with Cr
substitution. For dilute Cr compositions, J_BB was estimated by mean-field
theory to be 2.0 meV. Despite the sizable Theta, long-range antiferromagnetic
order does not develop until very large x, and is preceeded by glassy behavior.
Data presented here, and that on dilute Al-substitution from Okuda et al.,
suggest that the reduction in magnetic frustration due to the presence of
non-magnetic Al does not have as dominant an effect on magnetism as chemical
disorder and dilution of the magnetic exchange. For all samples, the 5 K
isothermal magnetization does not saturate in fields up to 5 T and minimal
hysteresis is observed. The presence of antiferromagnetic interactions is
clearly evident in the sub-Brillouin behavior with a reduced magnetization per
Cr atom. An inspection of the scaled Curie plot reveals that significant
short-range antiferromagnetic interactions occur in CuCrO2 above its Neel
temperature, consistent with its magnetic frustration. Uncompensated
short-range interactions are present in the Al-substituted samples and are
likely a result of chemical disorder
