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

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-N b-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 λs and low Hk.