Magnetic, structural and magnetocaloric properties of Y${}_{0.9}$Gd${}_{0.1}$Fe${}_2$H${}_x$ hydrides

Abstract

At 300 K, Y${}_{0.9}$Gd${}_{0.1}$Fe${}_2$H${}_x$ hydrides crystallize sequentially with increasing H concentration in various structures related to a lowering of the cubic MgCu${}_2$ type structure of the parent alloy: cubic C1, monoclinic M1, cubic C2, monoclinic M2, cubic C3, orthorhombic O. Above 300 K, they undergo a first-order transition at a T${}_{O-D}$ temperature driven by order-disorder of hydrogen atoms into interstitial sites. Their magnetic, structural and magnetocaloric properties have been investigated through magnetic measurements, and high-resolution synchrotron diffraction experiments. The magnetization at 5 K decreases slightly from 4 to 3.8 ${\mu }_B$ for x = 3 to 3.9 H f.u., then with a larger slope for higher H content. A discontinuous decrease of the magnetic transition temperature is observed: M1 and C2 hydrides are ferrimagnetic with T${}_C$ near 300 K, M2 hydride displays a sharp ferromagnetic-antiferromagnetic transition at T${}_{FM-AFM}$ =144 K, whereas C3 and O hydrides present only a sharp increase of the magnetization below 15 K and a weak magnetization up to RT. Negative magnetic entropy variations ($\Delta$S${}_M$) are measured near T${}_C$ for the M1 and C2 phases, near T${}_{FM-AFM}$ for the M2 phase, whereas positive $\Delta$S${}_M$ peaks due to inverse MCE effect are found near T${}_{O-D}$. A structural and magnetic phase diagram is proposed.

8 pages (published), 7 figures, 46 references

References in corpus (4)

• Correlation between magnetism and magnetocaloric effect in RCo2-based Laves phase compounds
• Origin of the metamagnetic transitions in Y1-xErxFe2(H,D)4.2 compounds
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