A correlation between the spin wave stiffness constant and the cation size disorder in the perovskite manganites

We investigated the temperature dependence of magnetization in the ferromagnetic phase of La 0.67−2 x Nd 2 x Ca 0.33− x Sr x MnO 3 (x=0, 0.1, 0.02 and 0.33) manganites in terms of the spin wave theory. A relation between the spin wave stiffness constant ( D) and the cation size mismatch was obtained. By means of this relation we could reproduce the values of D determined by different techniques reported in the literature for some samples. These findings may have important implications on the spin dynamics and the metallic electrical resistivity at low temperatures.