Fe₂Ta thin films offer a rare earth free solution for magnetic refrigeration

Magnetic refrigeration technologies can provide a more eco-friendly and sustainable alternative to conventional refrigeration techniques, but often require using magnetic components comprised of rare earth materials.

Shaji et al. identify Fe₂Ta alloy thin films as a potential solution for enabling a carbon-free and rare earth element free magnetic refrigerator. Using c-plane sapphire as the substrate, they grew the Fe₂Ta alloy thin films using a composite Fe-Ta target and a pulsed laser deposition method. X-ray diffraction analyses indicate the alloy films have a MgZn2 type lattice structure.

The authors measured the films’ magnetic properties, including the field dependent temperature for the paramagnetic to antiferromagnetic transition. They investigated the magnetocaloric properties of the thin films using magnetization-based indirect measurements.

“The indirect measurements were based on determining the entropy change in the material solely based on magnetic measurements and thermodynamic arguments via Maxwell’s relation,” said author Dhananjay Kumar.

Compared to other magnetocaloric materials, which usually required higher magnetic fields to demonstrate magnetocaloric effects, Fe₂Ta thin films exhibit magnetocaloric effects at lower fields.

“It is difficult to achieve a very strong magnetic anisotropy in bulk materials without using rare-earth materials, but not impossible,” said author Dhananjay Kumar. “The difficulty is overcome by alloying Fe with Ta which is non-rare earth element.”

The authors are currently working to optimize the composition of the Fe-Ta alloy system in an effort to enhance its magnetic and magnetocaloric properties.

Source: “Magnetic and magnetocaloric properties of Fe₂Ta thin films,” by S. Shaji, Nikhil. R. Mucha, P. Giri, C. Binek, and D. Kumar, AIP Advances (2020). The article can be accessed at https://doi.org/10.1063/1.5134796 .