Quantum Size Effect Exponential Heat Capacity in 4 nm Natural Nickel Nanolattice

TL;DR

This study reports the first observation of exponential heat capacity decay in 4 nm nickel nanoparticles at low temperatures, revealing quantum size effects and their influence on thermodynamic properties.

Contribution

It provides experimental evidence of quantum size effect-induced exponential heat capacity in nickel nanoparticles, a phenomenon predicted 79 years ago but not previously observed.

Findings

Exponential decay of heat capacity below 45.2 K observed

Magnetic fields have negligible effect on heat capacity features

Quantum size effects influence magnetic susceptibility behavior

Abstract

Quantum size effect-induced heat capacity of metal nanoparticles at low temperatures was predicted 79 years ago to be exponential. This, however, has not been reported until date. In defiance, we demonstrate here observation of exponentially decaying heat capacity, below 45.2 K, associated with quantum jumps, exceptionally in 4 nm naturally assembled hexagonal closed packed (hcp) lattice of nickel nanoparticles; high magnetic fields have negligible effect on these features. Magnetic susceptibilities in contrast reveal evolution of quantum size effects with decrease in particle size. They exhibit sharp rise below about 30 K and vestiges of saturations below 5 K. The former is explained by Curie-like characteristics of odd electrons while the latter tend towards the orthogonal even-like case. These characteristics, ascribed to the ensembles of Ni nanoparticles, will give a new direction in understanding this crucial thermodynamic phenome-non.