Designed materials with the giant magnetocaloric effect near room temperature

The coupling between structural and magnetic degrees of freedom is crucial for realization of interesting physical phenomena associated with magneto-structural transformations resembling austenite-to-martensite transitions. Despite substantial efforts in design and discovery of materials with strong magnetocaloric effects, a majority of viable candidates are composed of non-earth-abundant and toxic elements, while others involve challenging syntheses and post processing. Guided by advanced density functional theory calculations, we report a new family of compounds, i.e., Mn0.5Fe0.5Ni1-xAlx [x = 0.045-0.07] exhibiting a giant magnetocaloric effect (MCE) that is tunable near room temperature. Their MCE functionality arises from a distinct magneto-structural transformation between a paramagnetic hexagonal Ni2In-type phase and ferromagnetic orthorhombic TiNiSi-type phase that can be actuated by magnetic field and/or pressure. As the transition is sensitive to external hydrostatic pressure, the same materials should also exhibit a strong barocaloric response in addition to the giant MCE. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.