%0 Journal Article %A Yang, Minghui %A Oro-Sole, Judith %A Kusmartseva, Anna %A Fuertes, Alba %A Attfield, J. Paul %D 2015 %T Electronic tuning of two metals and colossal magnetoresistances in EuWO1+ xN2- x perovskites %U https://repository.lboro.ac.uk/articles/journal_contribution/Electronic_tuning_of_two_metals_and_colossal_magnetoresistances_in_EuWO1_xN2-_x_perovskites/9413039 %K untagged %K Physical Sciences not elsewhere classified %X A remarkable electronic flexibility and colossal magnetoresistance effects have been discovered in the perovskite oxynitrides EuWO1+xN 2-x. Ammonolysis of Eu2W2O9 yields scheelite-type intermediates EuWO4-yNy with a very small degree of nitride substitution (y = 0.04) and then EuWO1+xN 2-x perovskites that show a wide range of compositions -0.16 < x < 0.46. The cubic lattice parameter varies linearly with x, but electron microscopy reveals a tetragonal superstructure. The previously unobserved x < 0 regime corresponds to oxidation of Eu (hole doping of the Eu:4f band), whereas x > 0 materials have chemical reduction of W (electron doping of the W:5d band). Hence, both the Eu and W oxidation states and the hole/electron doping are tuned by varying the O/N ratio. EuWO1+xN2-x phases order ferromagnetically at 12 K, and colossal magnetoresistances (CMR) are observed in the least doped (x = -0.04) sample. Distinct mechanisms for the hole and electron magnetotransport regimes are identified. © 2010 American Chemical Society. %I Loughborough University