You can download following Core Loss Files free. Each Core Loss File (in excel) contains the digital data on core loss data (core loss vs. flux density) at a specific frequency. Some may contains several core loss curves at upto 5 frequencies.

Electrical Steel NGO – AK Steel’s M-19

Electrical Steel GO – ATI’s M-6

Cobalt Steel – Carpenter’s 50A

Metglas – 2605SA1

Nickel Steel – Carpenter’s 49 NGO

Low Carbon Steel – Mild Steel

Iron Powder Core – Micrometals -30 material

Alloy Powder Core – Magnetics’ KoolMu 40mu

Ferrite – Magnetics P material

MHz Ferrite – Ferroxcube 3B1