Method for the manufacture of a nanocrystalline magnetic core

A method for the manufacture of a magnetic core comprising the steps of:

• first, winding an amorphous tape of a soft magnetic nanocrystallizable alloy possessing a first coefficient of thermal expansion onto a carrier made of a material possessing a second coefficient of thermal expansion, wherein the second coefficient of thermal expansion is larger than the first coefficient of thermal expansion;
• second, subjecting the wound tape and carrier to a first thermal treatment, wherein the first thermal treatment is configured such that it causes tension to be introduced into the tape by thermal expansion of the carrier, although the alloy remains in an amorphous state, and then removing the carrier from the wound tape after cooling of the wound tape and the carrier;
• and
• third, following the cooling a second thermal treatment of the wound tape without the carrier, wherein the second thermal treatment is configured such that the amorphous alloy structure is transformed into a nanocrystalline alloy structure with at least 50% of the alloy structure being formed of fine crystalline particles having an average particle size of 100 nanometers or less.