Role of the stability of charge ordering in exchange bias effect in doped manganites.

In this work we have carried out an elaborate study on the magnetic properties and investigated the exchange bias phenomena of some charge-ordered (CO) manganites. The detailed study of Sm Ca MnO (x = 0.5, 0.55, 0.6, 0.65, 0.7) compounds shows that SmCaMnO, which is the most robust charge ordered material studied here, shows significantly large exchange bias field (H) as compared to the other compounds. Our experimental results and analysis indicate that T, which reflects the stability of the charge-ordered state, is one of the key parameters for the exchange bias effect. Similar behaviour is found in other rare-earth analogues, viz., La Ca MnO and Pr Ca MnO compounds as well. We also found that with increasing stability of CO states in Sm Ca MnO compounds, H enhances due to increase in number and reduction in size of ferromagnetic clusters.