Colossal enhancement of electrical conductivity in Y2Ir2O7 nanoparticles
  We present a comparative study of the magnetic and electrical properties of polycrystalline and nanocrystalline Y2Ir2O7, 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 pentavalent oxidation state of Iridium 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. 
Vinod Kumar Dwivedi, Abhishek Juyal and Soumik Mukhopadhyay
cond-mat.str-el