Influence of short time milling in R5(Si,Ge)4, R =Gd and Tb, magnetocaloric materials

TL;DR

This study examines how short-term milling affects the structural, magnetic, and magnetocaloric properties of Gd and Tb-based R5(Si,Ge)4 materials, revealing contrasting effects on magnetocaloric performance.

Contribution

It demonstrates that short milling times can modify particle size and magnetic coupling, leading to either enhancement or reduction of the magnetocaloric effect in these materials.

Findings

Gd-based material's magnetocaloric effect decreases by 35% after milling.

Tb-based material's magnetocaloric effect increases by 23% due to internal strain.

Milling induces structural and magnetic transition coupling changes.

Abstract

The effect of the short milling times on R5(Si,Ge)4 R =Gd, Tb magnetocaloric material properties was investigated. In particular, the effect of milling on atomic structure, particles size and morphology, magnetic, and magnetocaloric effect was studied. With short milling times (< 2.5h), a reduction of the Gd5Si1.3Ge2.7 and Tb5Si2Ge2 particles size was achieved down to approximately 3.5 DSm. For both compositions the main differences are a consequence of the milling effect on the coupling of the structural and magnetic transitions. In the Gd5Si1.3Ge2.7 case, a second-order phase transition emerges at high temperatures as a result of ball milling. Consequently, there is a decrease in the magnetocaloric effect of 35% after 150 minutes of milling. Interestingly, an opposite effect is observed in Tb5Si2Ge2 where a 23% increase of the magnetocaloric effect was achieved, driven by the enhancement of the coupling between magnetic and structural transitions arising from internal strain promoted by the milling process.