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

Abstract

We have studied the magnetic properties of ion doped MnFe (Formula presented.) O (Formula presented.) nanoparticles with the help of a modified Heisenberg model and Green’s function theory taking into account all correlation functions. The magnetization (Formula presented.) and the Curie temperature (Formula presented.) increase with decreasing particle size. This is the opposite behavior than that observed in CoFe (Formula presented.) O (Formula presented.) and CoCr (Formula presented.) O (Formula presented.) nanoparticles. By Co, Mg or Ni doping, (Formula presented.) and (Formula presented.) 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 (Formula presented.) 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 (Formula presented.) is field dependent.