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 < xL with the limiting concentration xL = 0.01 for Co doping and xL = 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 VL decreases up to x = xL. For x > xL, μ dramatically decreases toward zero and VL increases, the latter suggesting interstitial doping. Thermoelectric measurements showed that the samples are n-type for x < xL and p-type for x > xL, suggesting that the RTFM is intrinsic and it is electron mediated.
Van Komen, Chadd and Punnoose, Alex. (2009). "Transition from N-Type to P-Type Destroys Ferromagnetism in Semiconducting Sn1-XCoxO2 and Sn1-XCrxO2 Nanoparticles". Solid State Communications, 149(47-48), 2257-2259. http://dx.doi.org/10.1016/j.ssc.2009.08.039