Enhanced coercivity in CoPtCr thin film media using CrV underlayer (abstract)

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Abstract
As the areal density of thin magnetic media continues to increase1,2 and aims toward 10 gigabits/in2, the future media’s magnetic properties and recording performance such as the coercive force and signal to noise ratio need to increase substantially.3 In this paper we report the use of a chromium vanadium underlayer as a method to control the microstructure and enhance the coercivity of CoPtCr media. To study the effect of the underlayer composition on microstructure and magnetic properties, CrV‐alloy/CoPtCr structures were fabricated with CrV‐alloy concentration ranging from pure Cr to pure V. The magnetic media target concentrations were Co75Pt12Cr13, Co74Pt9Cr17, and Co80Pt3Cr17. We observed that the coercivity increases as the vanadium concentration in the CrV alloy increases and peaks at 50 at. % V. The Cr50V50/CoPtCr yielded between 30% and 40% higher coercivity values than Cr/CoPtCr for the same thickness of underlayer and magnetic layer. The microstructures (by TEM) of the CrV underlayer and the CrV/CoPtCr show that the underlayer grains are largest at 50 at. % V and that the CoPtCr grains mimic those of the underlayer. There is also considerable amount of epitaxy between the (200) planes of the CrV and (110) planes of the CoPtCr. The increase in grain size and preferred orientation in the polycrystalline magnetic field is believed to affect the coercivity by reducing the magnetostatic coupling and increasing the magnetocrystalline anisotropy.4

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