Large magnetocaloric effect in free-standing Gd2O3 nanostructures near liquid helium boiling point

Abstract Magnetic and magnetocaloric properties of free-standing gadolinium oxide (Gd2O3) nanostructures have been studied. Nanoparticles of Gd2O3(Gd2O3-NP), nanorods of Gd2O3 (Gd2O3-NR) and a mixed system of Gd2O3nanosheets and nanorods (Gd2O3-NS+NR) have been prepared by template-free methods without the use of any surfactant or a catalyst. These samples crystallize in cubic crystal structure (space group Ia-3, no. 206, cI80). Magnetization measurements performed in the temperature range of 300 K to 5 K indicate typical paramagnetic behavior for all the samples. All three Gd2O3 nanostructures display large magnetocaloric effect at temperatures below ~10 K. While the maximum isothermal magnetic entropy change (ΔSm) value at 6 K is about -22.6 Jkg-1K-1 for the Gd2O3nanorods and -17.8 Jkg-1K-1 for Gd2O3 nanoparticles for a magnetic field change of 70 kOe, the mixed Gd2O3 nanosheets and nanorods system prepared by wet chemical method shows a maximum ΔSmvalue of -23.6 Jkg-1K-1 for the same field change. These are about 41% to 89% more than that of bulk Gd2O3. Therefore, Gd2O3-based nanostructures could be very useful for low temperature magnetic refrigeration applications.