steel

permeability is about same for all but the higher the C content the hygher the PM properties that is why low C steels are used for magnetic equipment in order to reduce remanence.

Permeability is highest in the Silicon Steels, and even better when the grains are oriented in the direction of field (usually by rolling directions)

These steels are almost universally used for electrical equipments.

However a basically Ni-Co-Fe alloy (Supermalloy) has a very high degree of permeability

Then we have Permendur and Supermendur Fe+Co+V (with permeability even higher than permalloy) -

some of them are listed in

http://hyperphysics.phy-astr.gsu.edu/HBASE/tables/magprop.html

of course out of syllabus we have Ceramics and Nano matrerials.