Small impurity-pinned solitons in layered antiferromagnets

Layered manganese-halide compounds exhibit quasi-two-dimensional magnetic behavior in the temperature region immediately above the ordering temperature where soliton excitation can be experimentally detected as an Arrhenius, exp(E/T), temperature-dependent electron paramagnetic resonance linewidth, where E is the soliton energy. When a nonmagnetic impurity such as magnesium is introduced into the Mn lattice, experimental linewidth data indicate that the excitation energy is dramatically reduced and the temperature range over which Arrhenius behavior is observed is widened to include higher temperatures. These effects occur for very small (less than 1%) impurity concentrations.