Scaling Analysis of the Magnetocaloric Effect in Co/Au Nanoparticles

Abstract

The system of superparamagnetic Co/Au bimetallic nanoparticles of average diameter 7 nm was investigated with respect to its magnetocaloric properties. DC magnetic measurements revealed the presence of field dependent zero field cooled M (T ) maximum (6-8 K) and significant zero field cooled/field cooled irreversibility at low temperatures in the system. Documented thermal hysteresis disallow standard magnetic entropy change calculation from isothermal M (H) data, thus we attempted to employ zero field cooled M (T ) data for this purpose. Magnetic entropy change was calculated employing the Maxwell relation. In maximal field variation of 1 T relative high magnetic entropy change for nanoparticles ∆SM ≈ 0.7 J/(kg K) at T = 9 K was observed. The data collapsed onto single universal curve after proper axis rescaling.