Large reversible magnetocaloric effect in GdPO4 nano-spherical particles at ultralow temperatures
M. Lassri, S. El Ouahbi, Imane Abdelrhafore, L.H. Omari, Abdelhadi El Hachmi, Hassan Hamouda, Benaissa Harradi, Y. Ounza, Gianluca Viscusi, Claire Minaud, Charafeddine Jama, H. Lassri
Abstract
This study reports the synthesis of gadolinium phosphate (GdPO 4 ) with a monoclinic crystal structure ( P2 1 / n ) using a high-temperature solid-state reaction method. Rietveld refinement of the X-ray diffraction (XRD) data revealed lattice constants of a = 0.66497(5) nm, b = 0.68457(5) nm, and c = 0.63327(4) nm. The magnetic and magnetocaloric properties of GdPO 4 were investigated in detail. The ferromagnetic (FM) to paramagnetic (PM) phase transition temperature was determined to be around 1.8 K. The transition was strongly supported by Arrott plots and a universal phenomenological curve describing the magnetocaloric effect (MCE). GdPO 4 exhibits significant magnetic entropy changes (−ΔS M ). The maximum values of - Δ S M max are 20.43 J/(kg·K) and 44.79 J/(kg·K) for a magnetic field change (μ 0 ΔH) of 2 T and 9 T, respectively. Our analysis indicates that the GdPO 4 nano-spherical particles exhibit short-range magnetic ordering, characterized by the coexistence of ferromagnetic (FM) and antiferromagnetic (AFM) interactions.