Specific heat anomalies and possible Griffiths-like phase in La0.4Ca0.6MnO3 nanoparticles

The specific heat of La0.4Ca0.6MnO3 in bulk and nanoparticle (∼60nm in grain size) forms was investigated. It is found that the charge-ordered state highly stabilized in the bulk samples can be significantly suppressed in the nanoparticle. The low temperature specific heat data reveal a Schottky-like anomaly at ∼5K for the bulk sample, while a large electronic linear term (γ=17.8mJ∕moleK2) was identified for the nanoparticle samples. The magnetic measurements unveil the small magnetic entropy as low as ∼0.255J∕kgK and the possible existence of a Griffiths-like phase in the nanoparticle samples. We argue that the physics underlying the size effect is associated with the dimension-dependent interactions based on which the ferromagnetic/charge-ordering transition occurs.