Size-dependent magnetocaloric effect in GdVO4 nanoparticles

We investigated the magnetization and electron spin resonance (ESR) in nanocrystals of antiferromagnet GdVO4 with the grain size ranging from 30 nm to 5 mu m. Our nanoparticles with an average size reduction from 5 pm to 300 nm exhibited enhanced paramagnetic-like behavior, in which the weakly coupled spins can be well aligned along the direction of an external magnetic field, resulting in a giant entropy change of -Delta S-M = 45 J/kg K at 3 K for Delta H = 7 T. Moreover, with a further reduction of grain size to similar to 30 nm, the saturation magnetization together with the negative entropy change -Delta S-M,S- max decreased dramatically. The aggregation effect is believed to be responsible for the decline in -Delta S-M,S- max in which small nanoparticles agglomerating to 'large' grains made them behave like bulk material. Finding the critical point of positive size effect on magnetocaloric effect offered a new way to achieve large magnetic entropy change. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The magnetization and electron spin resonance in nanocrystals of antiferromagnet GdVO4 were investigated, showing enhanced paramagnetic-like behavior with smaller grain sizes. Further reduction in grain size to around 30 nm resulted in dramatic decrease in saturation magnetization and negative entropy change. The aggregation effect was believed to be responsible for this decline.