Fluxtrol 75 - a trade name of high-frequency magnetic material manufactured by Fluxtrol Inc. There is a whole class of materials named Fluxtrol. 1)
Fluxtrol 75 is designed to be used in flux concentrators for induction heating. The number in the name refers to the value of magnetic relative permeability.
by S. Zurek, Encyclopedia Magnetica, CC-BY-3.0