S.H. Kong

Fe-Co-B/Ni-Fe soft magnetic underlayer with high saturation magnetization for perpendicular magnetic recording media

In this study, we introduce Fe-Co-B/Ni-Fe double layer with high saturation magnetization, low coercivity, high anisotropy field and high resonance frequency for soft magnetic underlayer in perpendicular magnetic recording media.

Improvement of soft magnetic properties of Fe–Co–B underlayer with large saturation magnetization by Ni–Fe–O seedlayers

Fe–Co–B layers were investigated for a soft magnetic underlayer with large saturation magnetization 4πMs in perpendicular magnetic recording media. The addition of B was examined to see the decrease of in-plane coercivity Hc∥ in the Fe–Co layer. The surface morphology of the films observed by atomic force microscopy revealed that each of the grains in the Fe–Co–B layer seemed to be separate. These separate grains seemed to cause the suppression of exchange coupling between grains in polycrystalline ferromagnetic films. A Ni–Fe–O seed layer was effective in reducing the grain size of the Fe–Co–B layer and inducing high uniaxial in-plane magnetic anisotropy. The grain size of the Fe–Co–B layer deposited on the Ni–Fe–O seedlayer was about 73% that of a Fe–Co–B single layer. The magnetic anisotropy field Hk was as high as 255 Oe in the Fe–Co–B/Ni–Fe–O layer. Furthermore, the relative permeability μr of Fe–Co–B/Ni–Fe–O was about 200 and the resonance frequency fr was above 3 GHz. Insertion of a Ni–Fe–O interla...

Evaluation of magnetic interactions in a double-layered perpendicular magnetic recording media using ferromagnetic Hall effects

A new method for evaluating magnetic interactions among particles in the recording layer (RL) with a soft magnetic underlayer (SUL) in a double-layered perpendicular magnetic recording media has been demonstrated. Since the RL and SUL reveal Hall effect responses with different symmetries regarding the applied magnetic field, it is possible to not only detect the anomalous Hall voltage from the RL and the planar Hall voltage from SUL simultaneously, but also to extract and evaluate their properties individually. In order to evaluate the magnetic interparticle interactions in the RL, an evaluation index of the ΔV-plot, which corresponds to the ΔM-plot, estimated using a simple relation among the initial magnetization curve, the upper and lower branch of the major hysteresis loop, was introduced. The initial magnetization curve of Co–Cr–Ta RL in a Co–Cr–Ta(100 nm)/Ni–Fe(50 nm) double-layered thin film, can be evaluated from the Hall voltage in positive and negative range of applied magnetic field using the ...

Oxide seed layer with low surface energy to attain fine grains in magnetic layers

The relationship of surface energy γs to the seed layers, grain size, and crystallite orientation of the recording layer is discussed. The oxide seed layer with lower γs is effective in attaining fine grains in magnetic upper layers. The grain size of a Co–Cr–Ta recording layer deposited on an oxide seed layer with lower γs is about 50% that of a recording layer deposited on a metallic seed layer with higher γs. The reduction in grain size in the recording layer with a Ni–Fe–O seed layer led to suppression of the noise level in the high recording density region. Furthermore, the grain size of the Fe–Co–B soft magnetic layer on the oxide seed layer with 27 mN/m γs, which corresponds to 75%–50% that of metallic films, also reduced to about 70% that of the Fe–Co–B single layer. The material of the magnetic upper layer on the seed layer with low γs may consist of very small dense island grains in the region of initial film growth, due to its high diffusion energy. These small dense nucleation sites in the reg...

Mn–Zn spinel ferrite thin films prepared by high rate reactive facing targets sputtering

Mn–Zn ferrite thin films were deposited by sputtering a Mn0.6Zn0.4Fe2 alloy target, which was fabricated by powder metallurgy, in a mixture gas of Ar and O2. A 12 nm thick Pt underlayer was deposited at a substrate temperature of 300 °C. All specimen films were prepared in a reactive facing targets sputtering system. The degree of oxidization of the film is strongly related to the oxidation condition at the surface of the target. The surface condition of the target can be estimated by monitoring the discharge voltage. The discharge current–voltage characteristics clarify that there are three regions for the surface condition of the target, i.e. “oxidized,” “metallic,” and “transition.” Mn–Zn ferrite films with (111) crystallite orientation were deposited on Pt(111) underlayer under the transition region condition. The film prepared at O2 partial pressure ratio of 25% revealed 4.8 kG of saturation magnetization 4πMs. The deposition rate of the reactive sputtering method is 16 times as high as that of the c...

[Ni-Fe/Si] double seedlayer with low surface energy for Fe-Co-B soft magnetic underlayer with high H/sub k/ for perpendicular magnetic recording media

Fe-Co-B layers deposited on Ni-Fe seedlayer exhibited a high in-plane anisotropy field H/sub k/ of 280 Oe caused by inclined incident angle of sputtered particles. Ni-Fe/Si double seedlayer with low surface energy led to increase the effect of inclined incident angle. For more increase of the H/sub k/ in Fe-Co-B layer, a control of surface energy in Ni-Fe seedlayer was investigated. An improvement of closest packing plane (111) crystallites orientation led to reduce the surface energy in Ni-Fe layer. The adhesive force of Ni-Fe(10 nm) deposited on Si(2 nm) layer with (111) crystallites orientation exhibited 475 nN corresponding to about 65% of that of Ni-Fe(10 nm) single layer with random orientation. [Ni-Fe/Si] double seedlayer with lower adhesive force was effective in attaining a small crystallites size as well as finer grains in Fe-Co-B layer. Moreover, the H/sub k/ increased up to 380 Oe in Fe-Co-B layer on [Ni-Fe/Si] double seedlayer with lower adhesive force.

Effect of intermediate Layer at recording Layer/soft magnetic underlayer interface in perpendicular recording media observed by ferromagnetic Hall effect

Effect of the presence of a Pt intermediate layer (IL) between a 50-nm-thick CoCrPt recording layer (RL) and a 100-nm-thick NiFe soft magnetic under layer (SUL) has been studied using ferromagnetic Hall effect under the tilted magnetic field. CoCrPt RL with/without Pt IL between the RL and SUL revealed different inclination in the anomalous Hall voltage loop indicating the effect from the Ni-Fe SUL. Magnetic properties of the SUL, simultaneously detected from the Planar Hall voltage suggested the interaction effect between the CoCrPt RL and Ni-Fe SUL.

(Fe-Co/Si)/sub n/ multilayers with high saturation magnetization for backlayer of perpendicular magnetic recording media

Summary form only given. A storage layer with high perpendicular coercivity (H/sub c/spl perp//) is essentially required to achieve high recording density with high bit stability for perpendicular magnetic recording media. A new material with large 4/spl pi/M/sub s/ above 20 kG must be developed for a soft magnetic backlayer (BL) beneath the storage layer as well as a writing head material (T. Osaka et al, 1998) for keeping away deterioration of the writing field gradients by saturation of the BL. In this study, (Fe-Co/Si)/sub n/ multilayers with large 4/spl pi/M/sub s/ as well as low coercivity are introduced. Domain structure and soft magnetic characteristic of (Fe-Co/Si)/sub n/ multilayers (ML) were compared with those of the other BL materials to clarify their suitability for BL in perpendicular recording media.

Ni-Fe-O intermediate layer and [Ni-Fe/Si]/sub n/ laminated soft underlayer for backlayer of Co-Cr-Ta-Pt perpendicular recording media

Ni-Fe-O layers prepared by a natural oxidation method were examined for the intermediate layer between Co-Cr-Ta(-Pt) recording layers and soft magnetic [Ni-Fe/Si]/sub n/ multilayered backlayers in perpendicular magnetic recording media. [Ni-Fe/Si]/sub n/ multilayers exhibited soft magnetic properties and improved the c axis orientation of Co-Cr-Ta crystallites in the recording layer deposited on them. Ni-Fe-O intermediate layers were suitable to obtain a finer grain as well as epitaxial growth in Co-Cr-Ta(-Pt) recording layers. The intermediate layer was effective in reducing media noise for high recording density applications.

Soft magnetic underlayer with multilayer structure for perpendicular magnetic recording media

In this study, multilayers with non-magnetic interlayers for the SUL were prepared in order to improve the soft magnetic properties and surface smoothness as well as reduce the media noise originated from the configuration.