Magnetocaloric materials are a promising alternative to compression gas-based refrigeration and temperature control. These materials take advantage of the magnetocaloric effect, increasing temperature in the presence of a magnetic field. They can be used in refrigeration cycles in the same way as compressed gases but have a higher maximum Carnot efficiency and avoid the use of environmentally hazardous gases.

The best magnetocaloric materials are made with rare earth metals, which are desirable due to their large magnetic moments and operable temperature ranges. However, these metals are expensive and still environmentally toxic.

Sarkar et al. developed a nanostructured material featuring iron nanoparticles embedded in a titanium nitride thin-film matrix. Their material exhibits a strong magnetocaloric effect over a large range of temperatures and a high thermal conductivity without relying on expensive and toxic rare earth metals.

“Magnetic refrigeration is an emerging, innovative, and potentially low-carbon technology,” said author Dhananjay Kumar. “The work presented here is a contribution to a path to find a simple material system exhibiting a magnetocaloric effect over a broader range of temperatures.”

Employing iron nanoparticles gave the researchers control over the temperature response of their material. In heterostructures, the size of the nanoparticles affects the exchange coupling between clusters, which in turn controls the magnetocaloric response. Their design resulted in a substantial temperature change.

In subsequent experiments, the authors plan to vary the size of the nanoparticles to explore their effect on the material’s magnetocaloric response.

Source: “Large refrigerant capacity in superparamagnetic iron nanoparticles embedded in a thin film matrix,” by Kaushik Sarkar, Surabhi Shaji, Suchit Sarin, Jeffrey E. Shield, Christian Binek, and Dhananjay Kumar, Journal of Applied Physics (2022). The article can be accessed at