Microstructure and magnetic properties of a Co/Pd multilayer on a controlled Pd/Si seed layer for double-layered perpendicular magnetic recording media
An approach to fabrication of a patterned magnetic recording
medium for next generation data storage systems is presented.
(Co/Pd)n
magnetic multilayers are evaluated as candidates for patterned medium materials
for their high and easily controllable magnetic anisotropy. The multilayer films
deposited on a Ta seed layer enable high intergranular exchange coupling—an
essential feature of a patterned magnetic recording medium. The quality of
(Co/Pd)n
superlattices was optimized via deposition conditions and monitored using low-angle x-ray
diffraction. An estimated in-plane (hard-axis) magnetization saturation field in excess of
40 000 Oe was observed. Vertical (easy-axis) hysteresis loops for as-deposited continuous
magnetic multilayers exhibited a low coercivity of 930 Oe, indicating highly uniform
(magnetically) films with weak domain wall pinning. Ion-beam proximity lithography
was used to pattern magnetic multilayers into 43 nm islands on a 135 nm pitch.
Following patterning, easy-axis coercivity increased nearly 15-fold to 12.7 kOe.
͑Co/ Pd͒ N multilayers exhibit high vertical magnetic anisotropy and have been extensively explored as recording medium candidates for high density magnetic recording applications. In this work, ͑Co/ Pd͒ N multilayers are deposited by magnetron sputtering and patterned into large periodic arrays of 200 nm islands to enable controlled domain wall injection for quantitative comparison of magnetic anisotropy energies. Magnetic properties are correlated with x-ray photoelectron spectroscopy data, an approach commonly used to probe the binding energies and valence band positions. Confirming theoretical predictions, it is demonstrated that the degree of d-shell hybridization at Co/Pd interfaces directly correlated with the magnitude of magnetic anisotropy.
Ion irradiation of continuous and patterned (Co∕Pd)n magnetic multilayer films has been studied as a mean to control magnetic anisotropy as well as to evaluate possible ion irradiation damage involved in ion-beam proximity lithography patterning. The coercivity of patterned medium was found to decrease from 11kOe for as patterned samples to 0.3kOe for samples with 800μC∕cm2 ion irradiation. Remnant squareness of the patterned samples remained essentially unchanged. As the number of bilayers increases in the sample, the effects vary, suggesting that several mechanisms of damage occur. Significantly, for typical irradiation doses used in ion-beam proximity lithography, no measurable alteration of magnetic properties was observed.
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