Critical and High-Temperature Spin Dynamics in Two 3-D and Two 2-D Ferromagnets
The uniform relaxation rate for H=0 in 2-dim. Cu(CnH2n+1NH3)2Cl4 (n=1,2) and 3-dim. CuX2Br4.2H2O (X=Rb,NH4) has been measured from Tc-room temperature and compared with theory in the oritical region.The agreement is satisfactory if antisymmetric exchange is included. Comparison of (x.e−1 T)critical vs. ε for the four compounds shows universal behaviour.