PURPOSE: To obtain a medium, whose θK is large and S/N ratio is excellent, by including one or more kinds of elements in an I A group and a IIA group into a group into a thin amorphous alloy film, which has an easy magnetizing axis in the vertical direction with respect to the film surface.

CONSTITUTION: In a thin amorphous alloy film, which has an easy magnetizing axis in the vertical direction with respect to the film surface, one or more kinds of Li, Na, K, Rb, Cs, Fe, Be, Mg, Ca, Sr, Ba and Ra are included. Said alloy has a composition expressed by, e.g., a general formula (RXT1-X)1-YMY; where R is one or more kinds of Gd, Tb and Dy; T is one or more kinds of Co, Fe and Ni; M is one or more kinds of elements in said I A group and a II A group; X is in 0.1≤X≤0.4; and Y is in 0.01≤Y≤0.4. Said thin film is formed by a sputtering apparatus, a vacuum evaporation apparatus, an ion plating apparatus and other electroless plating method.