Finite size effects on the magnetocaloric properties around blocking temperature in γ-Fe2O3 nanoparticles

• Published in: Physica A 2019-06, Vol.523, p.260-267
• Main Authors: Elouafi, A., Moubah, R., Derkaoui, S., Tizliouine, A., Cherkaoui, R., Shi, S., Bendani, A., Sajieddine, M., Lassri, H.
• Format: Article
• Language: English
• Subjects: Blocking temperature; Magnetic entropy change; Magnetic nanoparticles; Magnetic refrigeration; Magnetocaloric effect
• ISSN: 0378-4371; 1873-2119
• DOI: 10.1016/j.physa.2019.02.039

We investigate the magnetocaloric properties of γ-Fe2O3 nanoparticles with an emphasis on size effects. The magnetic measurements have demonstrated that the properties are relevant for spin glasses at low temperature. The blocking temperature (TB) was found to decrease from 208 to 94 K with decreasing average size  from 8.5 to 2.7 nm due to surface effects. The temperature dependence of the magnetic entropy change (-ΔSM) was calculated from the isothermal magnetization. The caret shape of the (-ΔSM) curves shows that the magnetic transition near TB is a phase transition in line with Arrott plots. Under a magnetic field change of 10 kOe, the (- ΔSM) and the relative cooling power increase from 1.07 to 1.4 J/kg.K and 26 to 94 J/kg with increasing  from 2.7 to 8.5 nm, respectively. The increase of the magnetocaloric performance with increasing size was attributed to the increase in magnetization. •The magnetocaloric properties of γ-Fe2O3 nanoparticles were investigated.•The magnetocaloric performance was found to increase with increasing particle size.•The increase of the magnetocaloric properties with increasing size was attributed to the increase in magnetization.