Magnetometry is shown to be a unique tool to evaluate microstructure evolution in mixed metal oxides exposed to various redox conditions, relevant to applications such as catalysis, solid oxide fuel cells, and solar thermal water splitting. Different magnetic responses are elicited for: (1) the undoped ceramic; (2) metallic ions in solution; (3) metallic ions as a second phase oxide; and (4) metal particles that have exsolved. An example is provided for yttrium doped barium zirconate (BZY) containing nickel under different processing conditions.