Abstract: A thin film disk and a disk drive using the thin film disk are described. The disk has a thin film magnetic layer composed of small acicular grains having an average aspect ratio greater than one which results in improved recording performance. The development of the acicularity is aided through the crystal structure having anisotropic inplane stress with a radial stress being less than a tangential stress. The preferred magnetic material is an alloy cobalt which includes a glass forming material such as boron, boron oxide, silicon, silicon oxide, carbon, phosphorus, etc. The typical hcp unit cells form acicular grains with a tendency for the C-axis to be orthogonal to a long axis of the acicular grains. Preferably the C-axis of the grains is oriented along the circumferential direction of the disk. Preferably the underlayer is sputtered deposited using negative bias.