Paramagnetic Spin Correlations in Colossal Magnetoresistive La0.7Ca0.3MnO3

TL;DR

This study uses neutron spectroscopy to reveal dynamic, short-range spin correlations in La0.7Ca0.3MnO3 at temperatures above its Curie point, showing complex scattering features and robust paramagnetic spin behavior.

Contribution

It uncovers unexpected ridges of quasielastic scattering and detailed spin correlation patterns in the paramagnetic phase of La0.7Ca0.3MnO3, advancing understanding of spin dynamics in colossal magnetoresistive materials.

Findings

Discovery of ridges of quasielastic scattering along specific directions.

Observation of well-defined short-range spin correlations up to 28 meV.

Evidence of complex spin diffusion and additional scattering components.

Abstract

Neutron spectroscopy measurements reveal dynamic spin correlations throughout the Brillouin zone in the colossal magnetoresistive material La0.7Ca0.3MnO3 at 265 K (approximately 1.03 Tc). The long-wavelength behavior is consistent with spin diffusion, yet an additional and unexpected component of the scattering is also observed in low-energy constant-E measurements, which takes the form of ridges of strong quasielastic scattering running along (H 0 0) and equivalent directions. Well-defined Q-space correlations are observed in constant-E scans at energies up to at least 28 meV, suggesting robust short-range spin correlations in the paramagnetic phase.