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

The specific heat of La0.4Ca0.6MnO3 in bulk and nanoparticle (similar to 60 nm 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 similar to 5 K for the bulk sample, while a large electronic linear term (gamma=17.8 mJ/mole K-2) was identified for the nanoparticle samples. The magnetic measurements unveil the small magnetic entropy as low as similar to 0.255 J/kg K 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. (c) 2008 American Institute of Physics.