Magnetization, Band Gap and Specific Heat of Pure and Ion Doped MnFe2O4 Nanoparticles

Abstract

We have studied the magnetic properties of ion doped MnFe2O4 nanoparticles with the help of a modified Heisenberg model and Green’s function theory taking into account all correlation functions. The magnetization Ms and the Curie temperature TC increase with decreasing particle size. This is the opposite behavior than that observed in CoFe2O4 and CoCr2O4 nanoparticles. By Co, Mg or Ni doping, Ms and TC increase with enhancing the dopant concentration, whereas, by La or Gd doping, the opposite effect is obtained due to the different doping and host ionic radii which change the exchange interaction constants. The band gap energy Eg is calculated from the s–d model. It can decrease or increase by different ion doping. The peak observed in the temperature dependence of the specific heat at TC is field dependent.