  Frequency conversion is a widely realized physical process in nonlinear
systems of optics and electronics. As an emerging nonlinear platform,
spintronic devices have the potential to achieve stronger frequency conversion.
Here, we demonstrated a microwave frequency conversion method in a hybrid
quantum system, integrating nitrogen-vacancy centers in diamond with magnetic
thin film CoFeB. We achieve a conversion bandwidth ranging from 0.1 to 12GHz,
presenting an up to $\mathrm{25^{th}}$ order frequency conversion and further
display the application of this method for frequency detection and qubits
coherent control. Distinct from traditional frequency conversion techniques
based on nonlinear electric response, our approach employs nonlinear magnetic
response in spintronic devices. The nonlinearity, originating from the symmetry
breaking such as domain walls in magnetic films, presents that our method can
be adapted to hybrid systems of other spintronic devices and spin qubits,
expanding the application scope of spintronic devices and providing a promising
on-chip platform for coupling quantum systems.
