Abstract
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 Sm1−xCaxMnO3 (x = 0.5, 0.55, 0.6, 0.65, 0.7) compounds shows that Sm0.4Ca0.6MnO3, which is the most robust charge ordered material studied here, shows significantly large exchange bias field (HE) as compared to the other compounds. Our experimental results and analysis indicate that TCO, 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., La1−xCaxMnO3 and Pr1−xCaxMnO3 compounds as well. We also found that with increasing stability of CO states in Sm1−xCaxMnO3 compounds, HE enhances due to increase in number and reduction in size of ferromagnetic clusters.
Highlights
Ferromagnets, under exposure to a cyclic magnetic field, exhibit a magnetic hysteresis loop (M-H loop) resulting in energy storage in the system[1]
Since the exchange bias originate from the pinned interface spins between adjacent FM and AFM domains, HE depends on the surface area of the FM clusters dispersed in CO/AFM matrix
In this work, we propose that the robustness/stability of CO system, that is defined by the magnetic field required to melt the CO-state, must be an important parameter in deciding the value of HE in bulk CO manganite
Summary
The temperature derivative of M(T) exhibit an anomaly around Tf indicating the spin freezing behaviour in the Sm1−xCaxMnO3 (x = 0.5, 0.55) bulk compounds studied here (inset II: Fig. 1c,d) This effect, has not been observed in Sm0.4Ca0.6MnO3-nano, within the resolution limit of measurement. Increase in HE below 35 K was observed previously in Pr1/3Ca2/3MnO3 manganite system (which do not exhibit any prominent cusp at low temperature) and was ascribed to the glassy behavior of the compound[14] This indicates that the EB effect originates below Tirr (~TN), i.e. with the formation of FM clusters and increases drastically below freezing temperature in all the bulk Sm1−xCaxMnO3 (x = 0.5, 0.55, 0.6) compounds.
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