MULTICALORICS · Multicaloric refrigeration enhanced by multisite interactions: Bridging theory and experiment

Enhancing the efficiency and reducing the contaminant fingerprint of refrigeration and air conditioning are crucial in adapting to climate change and responding to high-energy demands, but cooling engines are presently dominated by low-performance refrigerants exploiting the compression of greenhouse harmful gases. Refrigeration exploiting magnetism has thus become a promising technology since it is environmentally friendly and more energy efficient. Typically, magnetic fields and mechanical stresses are applied to magnetic materials to generate cooling. However, this technology is still commercially unattractive because it relies on expensive neodymium-based permanent magnets to produce large enough magnetic fields and some mechanical materials suffer of fatigue that reduces their lifetime.I aim to advance both theoretical and experimental aspects of refrigeration based on magnetic materials by combining my expertise on theoretical magnetism with the know-how of experimentalists at the university of Barcelona on the experimental and thermodynamic study of solid-state materials. Our project focuses on two novel research directions: (1) The simultaneous application of magnetic and mechanical stimuli to reduce their magnitude and maximize the cooling effect. (2) The exploitation of a novel boost to cooling performance that I have recently predicted to arise from multisite interactions, which are complex interactions between atom-size magnetic degrees of freedom emerging from the cooperative behavior of many electrons gluing the magnetic material at the sub nano-scale. I will guide experimental efforts to overcome the performance limitations of current solid-state refrigeration in cost-effective magnetic materials by advancing the understanding of how to nanostructure magnetic materials with cooling power boosted by multisite interactions and by developing a new theory accounting for the coupling between the magnetism, the atom motion, and material elasticity.