Understanding the electronic, lattice, and magnetic contributions to the magnetocaloric
effect in magnetic materials can help to elucidate and optimize their performance.
In this work, the structural and magnetocaloric properties of Al-Mn-Ni alloy are experimentally
determined and theoretically analyzed based on ab initio calculations. The dominating
B2 phase associated with the Mn-rich sublattice is found to be responsible for the
observed magnetocaloric properties. The magnetic entropy change, refrigerant capacity,
and adiabatic temperature change are evaluated. Through the analysis of the data,
we find that for the B2 phase, changing from ferromagnetic to paramagnetic configurations
results in a pronounced elastic hardening despite the volume expansion. The decrease
in lattice entropy is significant and contributes negatively to the magnetic and electronic
entropy changes. Our work emphasizes the critical role of the lattice sector in the
magnetocaloric effect, and provides an in-depth understanding of the individual entropy
terms in magnetic solid solutions.
