A nitrogen-containing magnetic alloy film composed of T-M-X amorphous alloy film and (T-M-X)N nitride film, and another film having a composition represented by (T-M-X)N and being compositionally modulated (In both cases T is at least one element selected from the group of Fe, Co, Ni and Mn, M is at least one element selected from the group of Ti, Zr, Hf, Nb, Ta, Cr, Mo, W, Re and Ru, X is at least one element selected from the group of B, Si, Ge and Al, and N is nitrogen.) show excellent characteristics for magnetic head cores such as soft magnetic property and wear resistance.