Phase diagrams of pure and diluted low-anisotropy antiferromagnets: Crossover effects (invited)

Phase diagrams of 3D low-anisotropy easy-axis antiferromagnets are reviewed. The topics discussed include (1) mean-field theory and early experiments; (2) bicritical points in pure antiferromagnets; (3) effects of random fields on the behaviors near the Néel and bicritical points; and (4) lower critical dimension of the random-field Ising model. Some unsettled questions in the area of random fields are mentioned.