Tuning the magnetocaloric response of Gd7-xYxPd3 (2 ≤ x ≤ 6) alloys by microstructural modifications

Abstract

We investigated the influence of microstructural changes on the magnetic properties and the magnetocaloric response of the Gd7-xYxPd3 (2 ≤ x ≤ 6) alloys rapidly quenched by vacuum suction casting (rc-cast samples) and melt-spinning (melt-spun samples) techniques. Quenched-in structural disorder determines magnetic and magnetocaloric properties in both series of alloys. For the rc-cast samples two distinct magnetic transitions are visible. The peak at higher temperatures is related to the ferromagnetic/paramagnetic transition of the crystalline phase. In contrast, the peak observed at low temperatures is believed to be related to the ferro-para transition of the amorphous phase and/or a spin reorientation. The Gd7-xYxPd3 alloys in the form of rapidly cooled cast exhibit the magnetic transition temperatures at 262 K, 242 K, 202 K, 153 K and 9 K, for 2 ≤ x ≤ 6 respectively. Curie temperatures of the melt-spun Gd7-xYxPd3 alloys are much lower compared to the rc-cast samples. The melt-spun Gd5Y2Pd3 orders ferromagnetically below 90 K, while Gd4Y3Pd3, Gd3Y4Pd3, Gd2Y5Pd3 and GdY6Pd3 ribbons undergo the magnetic transformation at 65 K, 40 K, 25 K, and 9 K, respectively. Investigated ribbons exhibit almost doubled magnetic entropy change in comparison to the rc-cast samples. For instance, the -ΔSm value for melt-spun and rc-cast Gd5Y2Pd3 is equal to 6.31 Jkg-1K-1 and 3.64 Jkg-1K-1, respectively. Moreover, due to the large δTFWHM of the magnetic entropy change peak, both the melt-spun and rc-cast samples exhibit large relative cooling power (RCP), reaching 466 Jkg-1 (Δμ0H = 5 T) for the rc-cast Gd5Y2Pd3. RCP values are comparable to those of some potential magnetic refrigerants.