Method for producing metal foils

A method for producing metal foils made of nano-crystal soft magnetic material, the method comprising:

• preparing a metal foil made of amorphous soft magnetic material, wherein in the preparing the metal foil, a molten metal obtained by melting material of the metal foil is blown onto a rotating roll, and the molten metal is cooled and solidified on the roll to produce the metal foil made of the amorphous soft magnetic material, and wherein in the preparing the metal foil, the metal foil has an even surface and an uneven surface;
• and
• heating the metal foil while bringing the even surface of the metal foil into close contact with a base made of metal such that the metal foil conforms to a placement surface of the base and bringing the uneven surface of the metal foil into close contact with a support member with low thermal conductivity, to crystallize the amorphous soft magnetic material of the metal foil into the nano-crystal soft magnetic material,
• wherein in a crystallization, the metal foil is heated at a heating temperature to crystallize the amorphous soft magnetic material, the heating temperature being higher than or equal to a crystallization starting temperature at which the amorphous soft magnetic material crystallizes into the nano-crystal soft magnetic material and allowing a temperature of the placement surface to be lower than a temperature of the metal foil having temperature rise due to heat generated by self-heating during crystallization, and the base absorbs more heat generated by self-heating during crystallization than the support member, and
• wherein in the crystallization, bringing the even surface of the metal foil into close contact with the base includes sucking the even surface of the metal foil from a plurality of suction ports formed on the placement surface of the base such that the plurality of suction ports prevent local decrease of the temperature of the placement surface when the metal foil is in close contact with the base.