Abstract
While the spin dynamics of La0.7Ca0.3MnO3 in the ferromagnetic phase are known to be unconventional, previous measurements have yielded contradictory results regarding the damping of spin wave excitations. Neutron spectroscopy measurements on a sample with a transition temperature of Tc=257 K, higher than most single crystals, unambiguously reveal an anomalous increase in spin wave damping for excitations approaching the Brillouin zone boundary along the [100] direction that cannot be explained as an artifact due to a noninteracting phonon branch. Spin waves throughout the (HK0) plane display a common trend where the spin wave damping is dependent upon the excitation energy, increasing for energies above roughly 15 meV and reaching a full width at half maximum of at least 20 meV. The results are consistent with a model of intrinsic spatial inhomogeneity with phase separated regions approximately 18 Å in size persisting over a large range of temperatures below Tc.
