Magnetic properties and thermal stability of Co-TM-Zr (TM=Nb, Ta, Mo, W, and Ni) amorphous sputtered films for magnetic heads

Abstract

The magnetic properties and thermal stability Co-TM-Zr (TM=Nb, Ta, Mo, W, and Ni) amorphous films prepared by rf diode sputtering are investigated. Amorphous films with a homogeneous structure and coercive force Hc of less than 20 A m−1 are obtained at an argon gas pressure of 0.3–1 Pa. The formation range of the amorphous films is broad in the systems containing Ta and Nb, whereas it is limited to the composition range greater than 4–5 at % of Zr in the systems of Mo, W, and Ni. The magnetostriction λs depends on the concentration ratio of Zr and the TM. Films with zero λs are obtained at concentration ratios Czr/CTM ranging from 0.3 for Co-Nb-Zr films to 1.5–1.7 for Co-W-Zr films. The crystallization temperature Tx is highest in Co-Ta-Zr films and lowest in Co-Mo-Zr films when λs is zero and both films have the same saturation magnetic flux density Bs. The anisotropy field Hk is highest in Co-Ni-Zr films and lowest in Co-Nb-Zr films. These results indicate that Co-Ta-Zr and Co-Nb-Zr amorphous films are suitable for use as magnetic head materials because of the Co-Ta-Zr film's high Tx and Bs, and the Co-Nb-Zr film's small λns and low HK