Composition dependence of the spin wave stiffness parameter in La1−xCaxMnO3 CMR materials

Abstract Long-wavelength spin waves in La 1− x Ca x MnO 3 CMR materials exhibit conventional Heisenberg dispersion ( E = Dq 2 + Δ ), but with an anomalous temperature dependence for the spin dispersion parameter D . For x ≈0.33, near the optimum CMR composition, D remains approximately 50% of its T =0 K value before exhibiting a near-first-order transition at T c , instead of following the expected power law decrease as T approaches T c . No temperature hysteresis was observed in either D or in the magnetization. Compositions with x =0.40 and 0.45 show more conventional temperature renormalization.