Magnetocaloric effect in rare earth Ho2O3 nanoparticles at cryogenic temperature

• Published in: Journal of magnetism and magnetic materials 2020-04, Vol.500, p.166391, Article 166391
• Main Authors: Shinde, K.P., Nan, W.Z., Tien, M.V., Lin, H., Park, H.-R., Yu, S.-C., Chung, K.C., Kim, D.-H.
• Format: Article
• Language: English
• Subjects: Annealing; Antiferromagnetism; Cryogenic temperature; Crystal structure; Crystallinity; Electric arcs; Magnetism; Maximum entropy; Nanoparticles; Oxidation; Pattern analysis; Phase transitions; Refrigeration; Room temperature
• ISSN: 0304-8853; 1873-4766
• DOI: 10.1016/j.jmmm.2020.166391

•Ho2O3 nanoparticles prepared by oxidation of HoN nanoparticles.•Amorphous Ho2O3 converted into crystalline Ho2O3 by annealing.•Second-order antiferromagnetic phase transition occurs at cryogenic temperature.•MCE was found to be 22.4 J/kgK at ΔH = 5 T for crystalline Ho2O3. Magnetic refrigeration is becoming a promising technology to replace the conventional refrigeration techniques based on gas compression/expansion at cryogenic temperature as well as at room temperature. In the present study, we have fabricated Ho2O3 nanoparticles by oxidation of HoN prepared by plasma arc discharge. The Ho2O3 nanoparticles annealed at 1200 °C were investigated by the structural and magnetocaloric analysis. The XRD pattern confirms the amorphous nature of naturally oxidized Ho2O3, which was converted into crystalline by annealing. It has been discovered that crystalline Ho2O3 nanoparticles exhibit significantly larger magnetocaloric effect at cryogenic temperature, in comparison to the amorphous nanoparticles, with the second-order antiferromagnetic phase transition. The maximum entropy change was found to be 15.1 J/kgK and 22.4 J/kgK at an applied magnetic field of 5 T for amorphous and crystalline Ho2O3, respectively.