If the magnetising field on a ferromagnetic material is increased, its permeability [AIIMS 2015]

Magnetic permeability of substance,

$\mu =\frac{B}{H}\Rightarrow \mu \propto \frac{1}{H}$

where, H is the magnetising or magnetic field strength. As, the magnetising field of a ferromagnetic material is increasing thus its, permeability decreases.