Hoon-Sang Oh

Enhancement of coercivity by underlayer control in Co/Pd and Co/Pt multilayers

Co/Pd and Co/Pt multilayers were sputtered on Pd or Pt underlayers and the effects of sputtering pressure during the formation of underlayers on the magnetic properties of multilayers were investigated. It was found that the coercivity of Co/Pd multilayers was strongly dependent on the sputtering pressure of underlayer and could be increased drastically from 1.2 kOe up to around 5 kOe merely by increasing the sputtering pressure of Pd underlayer from 6 mTorr to 24 mTorr, while in case of Co/Pt films, no significant change of the coercivity could be observed with the variation of sputtering pressure of the underlayer. For both multilayers, the magnetic reversal feature was affected by the surface roughness of the underlayer and multilayers grown on the underlayer with a rough surface favored a rotation dominated process. The Kerr rotation angle was found to be hardly affected by the preparation conditions of the underlayer.

Dependence of sputtering power and soft underlayer on magnetic properties in CoCrPtO perpendicular recording media

In this paper, sputtering power dependence on magnetic properties and microstructure of CoCrPtO perpendicular recording media was examined. Also, change of magnetic properties of CoCrPtO layers on two different soft underlayers was investigated. As the oxygen gas ratio increases, coercivity (Hc) increases regardless of the variation of the sputtering power up to a certain critical oxygen gas ratio which depends on the sputtering power. Then, Hc drops sharply in all cases. The higher the power is, the higher the critical oxygen gas ratio is. As the oxygen gas ratio increases, exchange slope also decreases more rapidly at the lower sputtering power than higher power. The small grains of the size of /spl sim/7 nm with thick amorphous-like grain boundaries are observed in the media sputtered at the power of 75 W. It is considered that the selective oxidation of grain boundary is performed more effectively at low sputtering power. CoCrPtO layer on NiFeNb soft magnetic underlayer (SUL) showed higher Hc of 5000 Oe and well isolated grain in comparison with CoCrPtO layer on CoZrNb SUL. This difference of coercivity behavior may be associated with difference CoCrPtO layer on residual stress or surface roughness.

Effect Of Sputtering Pressure Of Pd Underlayer On The Perpendicular Magnetic Anisotropy In Co/Pd Multilayered Thin Films

The magnetic properties of Co/Pd multilayers, in particular the perpendicular magnetic anisotropy, have been analyzed as a function of the sputtering pressure of Pd underlayer. With an increase of sputtering pressure of the underlayer from 6 mTorr to 25 mTorr, perpendicular coercivity of the multilayers increased with a slight decrease of saturation magnetization, and the increment of the coercivity was larger for the films with thinner cobalt layers. From the anisotropy analysis, it was found that the interface anisotropy energy decreased from 0.390 erg/cm/sup 2/ to 0.255 erg/cm/sup 2/ because of the interface roughening of the multilayers, which was mainly responsible for the decrease of perpendicular anisotropy, while the volume anisotropy energy increased from -11.37/spl times/10/sup 6/ erg/cm/sup 3/ to -7.90/spl times/10/sup 6/ erg/cm/sup 3/. The abnormally large intrinsic volume anisotropy energies of the multilayers with thin cobalt layers (<7 /spl Aring/) appears to suggest the noticeable contribution of magnetoelastic effect to the perpendicular anisotropy of the films.