Development of Magnetocaloric Microstructures from Equiatomic Iron-Rhodium Nanoparticles through Laser Sintering

Pronounced magnetocaloric effects are typically observed in materials that often contain expensive and rare elements and are therefore costly to mass produce. However, they can rather be exploited on a small scale for miniaturized devices such as magnetic micro coolers, thermal sensors, and magnetic micropumps. Herein, a method is developed to generate magnetocaloric microstructures from an equiatomic iron-rhodium (FeRh) bulk target through a stepwise process. First, paramagnetic near-to-equiatomic solid-solution FeRh nanoparticles (NPs) are generated through picosecond (ps)-pulsed laser ablation in ethanol, which are then transformed into a printable ink and patterned using a continuous wave laser. Laser patterning not only leads to sintering of the NP ink but also triggers the phase transformation of the initial gamma- to B2-FeRh. At a laser fluence of 246 J cm(-2), a partial (52%) phase transformation from gamma- to B2-FeRh is obtained, resulting in a magnetization increase of 35 Am-2 kg(-1) across the antiferromagnetic to ferromagnetic phase transition. This represents a ca. sixfold enhancement compared to previous furnace-annealed FeRh ink. Finally, herein, the ability is demonstrated to create FeRh 2D structures with different geometries using laser sintering of magnetocaloric inks, which offers advantages such as micrometric spatial resolution, in situ annealing, and structure design flexibility.

Automated summary

A method has been developed to generate magnetocaloric microstructures from an equiatomic iron-rhodium (FeRh) bulk target. Paramagnetic near-to-equiatomic solid-solution FeRh nanoparticles are generated through picosecond-pulsed laser ablation in ethanol, and then transformed into printable ink and patterned using a continuous wave laser. FeRh 2D structures with different geometries can be created using laser sintering of magnetocaloric inks.