Effect of nanoscale size reduction on the magnetic properties of Pr_0.6Sr_0.4MnO₃

The ferromagnetic Pr_0.6Sr_0.4MnO₃ sample has been subjected to time bound high energy planetary ball milling with an aim to reduce the particle size. When the particle size is analyzed as a function of milling time, it is found that particle size decreases with increasing milling time and then saturates at a certain value. The implications of the decrease in particle size on magnetic properties have been carefully studied by analyzing the magnetization data in detail. With a decrease in particle size, the Curie temperature, T_C and the magnitude of magnetization drops. A deviation in inverse magnetic susceptibility from the Curie-Weiss behaviour has been noticed for nanoparticles which suggest the presence of quenched disorder due to particle size reduction. The strength of magnetic interactions switches from long range to short range with a systematic decrease in particle size. The observed properties can be explained considering the core–shell structure of the nanoparticle where the surface defects strongly influence the degree of disorder in the system.