Anomalous Specific Heat Behavior of Nanocrystalline Fe at Low Temperatures

The specific heat of nanocrystalline iron with grain size of 40nm has been measured in the low temperature range from 1.8 to 26K. The anomalous specific heat behavior of nanocrystalline iron is compared to that of the standard bulk iron. It is found that the electronic specific heat coefficient γ obtained at low temperatures decreases by about 50%. A T² term in the heat capacity associated with surface modes has been clearly observed. A large enhancement of the specific heat at temperatures above 16K may be interpreted as the Einstein oscillator contributions.