Magnetocaloric effect and the heat capacity of ferrimagnetic nanosystems in magnetic fluids

The specific heat capacity of a magnetite-based magnetic fluid and changes in the magnetic part of the molar heat capacity of its magnetic phase in magnetic fields of 0–0.7 T were determined calorimetrically over the temperature range 288–353 K. The temperature dependence of changes in the magnetic part of entropy in an applied magnetic field was calculated. It was found that the field dependence of heat capacity had a maximum in fields of 0.3–0.4 T, and the temperature dependences of changes in the magnetic part of heat capacity ΔC _p (H) and entropy ΔS _m(H) had maxima at the magnetic phase transition temperature.