Surface Ferromagnetism in Y2Sn2O7 Pyrochlore Nanoparticles

, No.227). In the light of literature that reflects on the frustration phenomenon in pyrochlore, single phase monodisperse Y2Sn2O7 nanoparticles with average crystallite size of 10 nm have been synthesized through hydrothermal method. The morphological studies indicate Y2Sn2O7 nanoparticles with size similar to 20 nm. DC magnetic measurements performed on Y2Sn2O7 nanoparticles illustrate an unusual bifurcation between zero-field cooled (ZFC) and field-cooled (FC) magnetization in magnetization vs temperature (M vs. T) measurements. The ferromagnetic loop is characterized by a coercivity of H-C = 240 Oe, and saturation magnetization, M-S = 0.66 emu/g significantly, even in the absence of any constituent magnetic ions in the sample. This is attributed to the ferromagnetic exchange interactions between the unpaired spins on the surface due to oxygen vacancies. In the absence of Van Vleck contribution to the magnetic susceptibility (chi), positive value of residual susceptibility, chi(0) at high-temperature end of chi vs. 1/T plot demonstrates the presence of ferromagnetic interactions on the surface. The presence of yttrium and tin in non-magnetic Y3+ (4d(0)5s(0)) and Sn4+ (5s(0)5p(0)) state through X-ray photo electron spectroscopic information authorizes the diamagnetic core of the nanoparticles in question. The antiferromagnetic behavior of the hysteresis loop at high field hints the presence of crystal lattice defects.