The United States Department of Energy’s Oak Ridge National Laboratory (ORNL) has been researching exotic materials for the development of solid-state cooling devices that do not rely on refrigerants or moving parts. The findings of this research, published in the journal Science Advances, have the potential to create more eco-friendly cooling solutions for various applications, including food, vehicles, and electronics.
One such material that has caught the interest of ORNL researchers is a nickel-cobalt-manganese-indium magnetic shape-memory alloy. This alloy can be deformed and then returned to its original shape by going through a phase transition, either by increasing temperature or by applying a magnetic field. The magnetic field induces a magnetic and structural phase transition in the material, which causes it to absorb and release heat due to the magnetocaloric effect. This effect could be utilized for refrigeration purposes, making the material a promising candidate for solid-state cooling applications.
In their investigations, the researchers conducted neutron scattering measurements to examine the magnetic field and temperature dependence of the phonons and magnons in the material with the formulation Ni45Co5Mn36.6In13.4. Phonons and magnons are quasiparticles that represent excited states in the quantization of the modes of vibrations and thermally excited spin waves that reduce the internal magnetization of magnetic materials, respectively.
Researchers discovered that these quasiparticles synchronize in small regions across the disordered arrangement of atoms that make up the material, and the patterns of behavior in these regions significantly influence the thermal properties of the material. These localized hybrid magnon-phonon modes modify the material’s phase stability, resulting in changes in the material’s properties and behavior that can be manipulated and tailored. According to ORNL, these investigations revealed that the cooling capacity of the material is tripled by the heat contained within the local magnon-phonon hybrid modes.
In comparison, a company called Frore Systems has introduced its own solid-state cooling technology, called AirJet. AirJet employs tiny membranes that vibrate at ultrasonic frequency to generate a flow of air, which removes heat from a heat spreader inside the device. Frore’s AirJet Mini technology was utilized in a mini PC from Zotac Technology, the ZBOX pico PI430AJ, to cool its Intel Core i3 processor. This example demonstrates another approach to solid-state cooling applications.