Electronic structure and large magnetocaloric effect in GdVO4 nanocrystals

Highlights: • Electronic structure and magnetocaloric effect (MCE) studies of GdVO₄ nanocrystals. • Large MCE with ΔS_max = 49 J/kg K at 2.6 K and RCP(RC)= 332 (239) J/K. • MCE of GdVO₄ comparable that of other potential materials usable to liquefy helium and hydrogen. • First-order transition and short-range order related to antiferromagnetism, surface spin disorders, and spin flop. -- Abstract: A sample of gadolinium orthovanadate (GdVO₄) nanocrystals crystallizing in the I4₁/amd tetragonal structure has been synthesized by a hydrothermal method. Electron microscope analyses have revealed the sample comprising gravel- and rod-shaped nanoparticles with the sizes of 30–80 nm. The magnetocaloric (MC) assessments upon the set of initial magnetization data have indicated a large MC effect in GdVO₄ nanocrystals. Under a magnetic-field change of 60 kOe, the largest magnetic-entropy change and relative cooling power are about 49 J/kg·K at 2.6 K and 332 J/K, respectively, which are comparable to the MC behaviors of their bulk samples. Such large MC values together with almost no magnetic hysteresis make GdVO₄ an excellent candidate for cryogenic magnetic refrigeration at low temperatures as liquefying helium and hydrogen. Analyzing in detail the magnetization and magnetic-entropy data versus the temperature and magnetic field, we have found GdVO₄ nanocrystals having short-range magnetic order, which is associated with the anti-ferromagnetic order, surface spin disorders, and spin flop.