When designing flyback transformer we need AL value for finding primary turns for required primary inductance. So what is the AL value in nH for MnZn 77 material?
AL changes with gap. https://www.tdk-electronics.tdk.com/inf/80/db/fer/e_25_13_7.pdf . Once you add a gap for flyback transformer, the material does not matter whether it be MnZn or nickel zinc. You can use the AL shown in the datasheet or calculate it yourself. Al = (u0 x ue)/(le/Ae) where ue = ui /(1+(gap*ui/le)) , ui is initial permeability which is 2900 for N30 material , 1750 for N27