The magnetic phase transition and magnetocaloric effect in Sm0.58Sr0.42MnO3 nanoparticles

• Size-induced first-to-second order phase transformation in perovskite manganite nanoparticles.
• Modification of the magnetocaloric effect.
• The oxidation-state shift of Mn in manganite nanoparticles.

It is known that Sm0.58Sr0.42MnO3 (SSMO) with a first-order magnetic phase transition exhibits colossal magnetoresistance and magnetocaloric effects around the Curie temperature (TC). However, the effects just occur in a narrow temperature range due to the first-order nature. This work points out that its phase transition width and magnetocaloric effect is easily modified upon the fabrication of SSMO nanoparticles (NPs). Our detailed studies also demonstrate a clear tendency of the magnetic phase transformation from first to second order when the crystallite size (d) of NPs are reduced below 65 nm. Though the d decrease usually leads to the suppression of the TC, magnetization, and magnetic-entropy change, the phase transition width is increased remarkably, thus widening the application range of SSMO. These interesting features are related to changes of the lattice strain, surface defect density, and electronic structure of Mn ions in NPs.