Not sure what you mean by "ferrite oxide" - no such thing. I assume you mean some mixture of iron oxides.
I would start with just some detergent, oxides are often in a dust form so at least some of it should go away.
Then, citric acid is a reasonably safe option.
Finally, hydrochloric acid could do the trick, but when dealing with acids there is always a risk they will destroy whatever you are trying to clean up. Depending on what is going on it can be better to leave the oxide as it is than to try to remove it. I would try with 1% acid first, to see if it works at all. 3% if the 1% is not satisfactory. Higher concentrations sound a bit risky.
Don't forget to rinse the surface with large amounts of water.