Colossal enhancement of electrical conductivity in Y₂Ir₂O₇ nanoparticles

We present a comparative study of the magnetic and electrical properties of polycrystalline and nanocrystalline $Y_2{Ir}_2{O}_7$, the latter prepared using a new chemical route. We find that reduction in particle size leads to enhanced ferromagnetism and orders of magnitude enhancement of electrical conductivity in the nanocrystalline sample. Based on x-ray photoelectron spectroscopy and x-ray absorption near edge structure spectroscopy results, the phenomenon is attributed to the increased fraction of Ir⁵⁺ and the resulting increase in double exchange interaction along with the weakening of spin–orbit coupling strength in the nanocrystalline sample compared to the bulk. (paper)