Sadayuki Watanabe

CoPtCr-SiO/sub 2/ granular media for high density perpendicular recording

A well isolated fine grain structure with large perpendicular magnetic anisotropy K/sub u/ is strongly required for CoCr based high density perpendicular recording media, in order to achieve low media noise performance and high thermal stability. A CoPtCrO magnetic layer has been proposed to enhance the segregated grains with an oxygen-rich grain boundary structure. The authors have already reported that the addition of SiO/sub 2/ to the CoPtCr recording layer is very effective in realizing a well isolated grain structure together with large K/sub u/ value, and also excellent recording performance and thermal stability. In this study, the microstructure, magnetic properties, and recording performance of the CoPtCr-SiO/sub 2/ perpendicular media are discussed in relation to the realization of high density recording media.

Magnetic properties, magnetic cluster size and read-write performance of CoPtCr-SiO/sub 2/ perpendicular recording media

In this study, we investigated magnetic properties, magnetic cluster size of CoPtCr-SiO/sub 2/ media and its read-write performance.

Exchange-coupled IrMn/CoZrNb soft underlayers for perpendicular recording media

An antiferromagnetic Ir-Mn pinning layer was applied to reduce the spike noise that originates from domain walls in a Co-Zr-Nb soft magnetic layer of perpendicular recording media. Blocking temperature was 285/spl deg/C and exchange-coupling energy of 0.22 erg/cm/sup 2/ was obtained by arranging a Co-Fe layer between Ir-Mn and Co-Zr-Nb films, without any thermal treatments to enhance the exchange-coupling field. Spike noise was successfully reduced over the entire disk area using a rapid thermal annealing process, and the total amount of noise generated from a soft magnetic layer decreased as the exchange bias field increased.

Recording performance of double-layered perpendicular recording media with an antiferromagnetic layer

In this study, we have investigated the layer structure and the materials of AFML to obtain high exchange bias field H/sub ex/, and also discussed the influence of the H/sub ex/ to the recording performance for double-layered perpendicular media.

Magnetic Properties to Optimize the

We calculated the optimal values of the first- and second-order uniaxial magnetic anisotropy energy terms, K_u1 and K_u2, for thermal stability and writability in perpendicular media which use the K_u2 effect. The magnetic energy barrier DeltaE for the remanent state with demagnetizing field 4pilangM _srang was calculated for various K_u1 and K_u2 values, and we obtained the grain volume V_grain to satisfy DeltaEV_grain/kT=60 for thermal stability (k is the Boltzmann constant, and T the absolute temperature). Moreover, the switching field was calculated assuming a saturation field less than 16 kOe for good writability. The K_u2 term enhances the DeltaE in the remanent state of magnetization, without a notable increase in H_s. It is concluded that the best langM_srang value to take advantage of the K_u2 effect is about 500emu/cm³, with K_u1=5times10⁶ erg/cm³ and K_u2=2.6times10⁶ erg/cm ³. The K_u2 term allows V_grain (and also the grain size) to be reduced by almost one-half, compared with a grain without a K_u2 term, while simultaneously achieving good thermal stability and writabilityIn the present study, the values of M_s, K_u2 and the first order uniaxial magnetic anisotropy energy term, K_ul, to utilize the K_u2 effect on the thermal stability whilst simultaneously achieving a good writability. The resulting ratio of DeltaE to H_s is discussed and compared to media without a K_u2 term.

K_u2

Summary form only given. The development of perpendicular HDDs has been constrained by the spike noise that originates from domain walls in soft magnetic layers. An antiferromagnetic (AFM) pinning layer is considered effective to reduce the noise (S. Watanabe et al, Proc. 2001 IEICE gen. conf., vol. 5, p. 35, 2001). However, it is not easy to obtain high exchange bias field (Hex) which is high enough to evade the spike noise. In this study, we reported on low noise media fabricated by the process tailored for mass production. An IrMn AFM layer and rapid thermal annealing (RTA) were employed in the process.

Effect in Perpendicular Recording Media

In this paper we analyzed a recording resolution and noise of perpendicular magnetic recording media with various layer thickness by MFM measurement of recording pattern with various linear recording densities.