Critical line broadening of the EPR in the two-dimensional antiferromagnet crystals Rb2MnCl4 and Rb2Mn0,8Cd0,2Cl4

Abstract The EPR spectrum of quasi-two-dimensional antiferromagnets Rb 2 Mn x Cd 1−x Cl 4 (x=1,0; 0,8) has been studied in a critical temperature range. Two theoretical approaches - the scaling theory and the soliton's theory - are used to explain experimental data on temperature of the EPR linewidth. In the first interpretation critical exponents are determined. For both crystal two temperature regions with different critical exponents are found. It is shown that the soliton's theory with an anomaleous great excitement energy describes the experimental data satisfactory.