Low Field Microwave Absorption in Mn:Ni Co-Doped ZnO μm Size Powders

Polycrystalline Zn1-x(Mn:Ni)xO sample for x = 0.02 were synthesized by solid state route.We have observed low field microwave absorption in these powder samples.Low field microwave absorption signal is out of phase with the regular resonance signal indicating the microwave absorption has a minimum at zero field and the absorption of microwaves increases with increase of magnetic field.Low field microwave absorption in these powders is qualitatively different from their bulk pellets.Temperature dependence of the low field microwave absorption indicates a line shape evolution and a non-monotonic peak to peak intensity change.Further, we have observed the absence of 2nd harmonic in this low field microwave absorption, indicating low field microwave absorption in these transition metal co-doped ZnO powders is not non-linear in nature.