Reversible low-field magnetoresistance in Sr2Fe2-xMoxO6-δ by oxygen cycling and the role of excess Mo (x>1) in grain-boundary regions

Oxygen cycling of Sr2Fe2-xMoxO6-delta (SFMO) samples allows the resistivity and low-field magnetoresistance (LFMR) to be precisely cycled. TEM shows that the change in resistivity with oxygen is not only a consequence of the change in oxygen stoichiometry of SFMO, but also a concomitant change in the Fe/Mo ratio in SFMO. The figure shows the change in MR and resistivity (values in m Omega cm above the data points for samples D1-D7) with increasing post-annealing time.