Goodwin, Daniel Harold

Measurements of magnetization versus temperature and field have been conducted on La1-xCaxMnO3 compounds which for some values of x exhibit colossal magnetoresistence (CMR). Recent theories propose that polaron forming double exchange interactions and Jahn-Teller distortions create a strong interaction amongst charge, spin and lattice degrees of freedom which is responsible for the unusually large magnotoresistence. In this work the enhancement of paramagnetic susceptibility is studied in order to investigate the possible existence of magnetic polarons. Enhancements of the effective moments are found in the range 0.15 < x < 0.94, which are qualitatively consistent with the existence of magnetic polarons. The findings are discussed within the framework of recent experimental and theoretical findings.