A research team led by the Department of Energy’s Oak Ridge National Laboratory has bridged a knowledge gap in atomic-scale heat motion. This new understanding holds promise for enhancing materials to advance an emerging technology called solid-state cooling.

An environmentally friendly innovation, solid-state cooling could efficiently chill many things in daily life from food to vehicles to electronics — without traditional refrigerant liquids and gases or moving parts. The system would operate via a quiet, compact and lightweight system that allows precise temperature control. 

Although the discovery of improved materials and the invention of higher-quality devices are already helping to promote the growth of the new cooling method, a deeper understanding of material enhancements is essential. The research team used a suite of neutron-scattering instruments to examine at the atomic scale a material that scientists consider to be an optimal candidate for use in solid-state cooling.

The material, a nickel-cobalt-manganese-indium magnetic shape-memory alloy, can be deformed and then returned to its original shape by driving it through a phase transition either by increasing temperature or by applying a magnetic field. When subjected to a magnetic field, the material undergoes a magnetic and structural phase transition, during which it absorbs and releases heat, a behavior known as the magnetocaloric effect. In solid-state cooling applications, the effect is harnessed to provide refrigeration. A key characteristic of the material is its nearness to disordered conditions known as ferroic glassy states, because they present a way to enhance the material’s ability to store and release heat.

Magnons, also known as spin waves, and phonons, or vibrations, couple in a synchronized dance in small regions distributed across the disordered arrangement of atoms that comprise the material. The researchers found that patterns of behavior in these small regions, referred to as localized hybrid magnon-phonon modes in the team’s paper detailing the research, have important implications for the thermal properties of the material. https://www.ornl.gov/news/scientists-probe-chilling-behavior-promising-solid-state-cooling-material