Random-field effects on the order in the diluted weakly anisotropic antiferromagnet K2NixZn1-xF4

With the use of neutron diffraction, the effects of random fields are studied in the diluted quadratic-layer antiferromagnet K2NixZn1-xF4 for x=0.96, 0.85, and 0.75. Upon cooling in external fields as small as H∼0.1 T, the systems quench into a nonequilibrium domain state characterized by the absence of long-range order along the c axis. At low Zn concentrations and low fields the interplane inverse correlation length follows κz∝ H0.71±0.03. The order within the planes is also affected, but remains unexpectedly long ranged.