Two-dimensional Ising behavior in c(2x2) antiferromagnetic Mn and Cr monolayers on Ag(001) -: art. no. 144419

The magnetic order M-S(T) is determined as a function of temperature for the c(2x2) antiferromagnetic monolayers of Mn and Cr on Ag(001), using the intensity of the coherent superlattice (1/2,1/2) reflections in low-energy electron diffraction to obtain the sublattice magnetization M-S. The data fit the Onsager-Yang theoretical result rather well for the spontaneous magnetization of the plane square lattice in the Ising model with critical temperatures T(C)approximate to198 and 462 K for Mn and Cr, respectively. Near T-C a fit to a universal power law M-S(T)similar to(1-T/T-C)(beta) confirms the two-dimensional Ising class with beta close to 1/8 and indicates the importance of second-order magnetic anisotropy in these two-dimensional antiferromagnets.