Rapid thermal annealing of amorphous and nanocrystalline soft-magnetic alloys in a static magnetic field

In this paper, we report on rapid thermal annealing (RTA) of two different soft-magnetic materials in a static magnetic field: amorphous Co-Nb-Zr and nanocrystalline Fe-Nb-N. RTA of Co-Nb-Zr films was investigated in an attempt to suppress the crystallization of Co during the induction of the anisotropy, thus extending the process window of this material in video-head manufacturing. Also, RTA of Fe-Nb-N was studied in an effort to promote the nucleation of nanocrystalline Fe grains, while suppressing the grain growth of α-Fe. Using RTA in a magnetic field, Co-Nb-Zr alloys can be heated to temperatures above 525°C, while suppressing the crystallization of hexagonal-close-packed Co. This temperature is considerably higher than that of conventional magnetic annealing in a furnace (400°C), and thus allows us to combine annealing with other high-temperature processes during recording head manufacturing procedures, such as glass bonding in sandwich head manufacturing. Furthermore, RTA allows the formation of nanocrystalline Fe-TM-N alloys with both a high permeability and a low magnetostriction (TM is a transition metal such as Zr, Hf, Nb, or Ta). Using high processing temperatures and short processing times, both the nucleation of bcc Fe and the segregation of NbN from Fe-Nb-N can be promoted, while the undesired grain growth of Fe is reduced, thus lowering the magnetic anisotropy. Moreover, layers produced in this way have increased resistivity to wear (during tape recording) than conventionally annealed layers.