The Cu/Mn atomic ratios obtained from ICP and EDS characterizations.

Sample	Cu/Mn atomic ratioa	Cu/Mn atomic ratiob
Undoped Mn3O4 sample	0	0
0.5 at% Cu-doped Mn3O4 sample	0.009	0.011
1 at% Cu-doped Mn3O4 sample	0.021	0.025
1.5 at% Cu-doped Mn3O4 sample	0.032	0.038
2 at% Cu-doped Mn3O4 sample	0.045	0.049

^aObtained from ICP.

^bObtained from EDS.