Transition from n-type to p-type destroys ferromagnetism in semiconducting and nanoparticles

This work reports strong correlations between the structural, magnetic and electronic properties of room temperature ferromagnets (RTFM) Sn1−xCoxO2 and Sn1−xCrxO2 for x = 0 to 0.1. The samples prepared by the sol–gel chemical method show RTFM for x < x L with the limiting concentration x L = 0.01 for Co doping and x L = 0.025 for Cr doping. As doping level x is increased from x = 0 , the magnetic moment per ion, μ , increases and the lattice volume V L decreases up to x = x L . For x > x L , μ dramatically decreases toward zero and V L increases, the latter suggesting interstitial doping. Thermoelectric measurements showed that the samples are n-type for x < x L and p-type for x > x L , suggesting that the RTFM is intrinsic and it is electron mediated.