Tom Donaly wrote:

Ferrites are notoriously non-linear, and thinking of them in
linear terms is liable to lead to disappointment. Look at
the manufacturer's data before you come to any conclusions regarding
how any of them behave.
73,
Tom Donaly, KA6RUH

Good advice. In antenna applications, we need to strive to keep the flux
density low enough that ferrites behave essentially linearly. If we
don't, harmonic generation will result.

Fortunately for us, the flux density decreases as frequency increases,
all else being equal. Also, many ferrites which are commonly used for
common mode chokes (current baluns), EMI filters, and the like will get
hot enough to explode before the flux density gets anywhere near saturation.

Roy Lewallen, W7EL