Particle size and interfacial effect on the specific heat of nanocrystalline Fe

The specific heat of nanocrystalline iron with grain size of 40 nm has been measured in the low-temperature range from 1.8 to 26 K. The anomalous specific heat behavior of nanocrystalline iron is compared with that of the normal polycrystalline iron. It is found that the electronic specific heat coefficient γ obtained at low temperatures decreases by about 50%. A quadratic temperature-dependent term associated with surface modes in the heat capacity has been clearly observed. A large enhancement of the specific heat at higher temperatures is interpreted as the Einstein oscillator contribution due to weakly bound atoms at the interfaces of the nanocrystals.