Underlayer For Perpendicular Recording Media Research Articles

Microstructure of CoNiFeB electroless-deposited soft magnetic underlayer for perpendicular recording media

The microstructure of a CoNiFeB film for a soft magnetic underlayer of perpendicular recording media, which was deposited by electroless plating on a Si wafer, has been investigated by transmission electron microscopy and a three-dimensional atom probe. After the deposition of the CoNiFeB film on a Ni underlayer, H c decreased from about 62 to about 3 Oe. Based on the microstructure observation results, the decrease of H c was concluded to be the result of reduced magneto-elastic energy. The good adhesiveness between the soft underlayer (SUL) and the Si substrate was found to be due to the composition gradient.

Investigations on annealed Ni–P in Al–Mg/Ni–P substrates as soft underlayer for perpendicular recording media

The amorphous Ni–P layer in the Al–Mg substrates of longitudinal recording media have been annealed to form soft magnetic underlayer for perpendicular recording media. After annealing at about 300°C for 10min, the Ni–P layer crystallized and was found to have Ni3P and Ni phases. The annealed samples were found to have soft magnetic properties. As the annealing temperature was increased, the samples showed a larger coercivity. The optical surface analyzer (OSA) results indicated that crystallized Ni–P could show lower noise than sputtered Ni-Fe thin films.

Novel laminated antiferro-magnetically coupled soft magnetic underlayer for perpendicular recording media

The magnetic characteristics of novel laminated antiferro-magnetically coupled soft magnetic underlayers (AFC-SULs) were investigated. The Co/Ru/Co structure is used as a basic unit for SULs. The antiferro-magnetically coupled soft underlayer with the structure of Glass/Ta (2 nm)/Cu (1.5 nm)/IrMn (8 nm)/Co 90Fe 10 (25 nm)/Ru (1 nm)/ Co 90Fe 10 (25 nm) showed significantly large exchange-bias fields of upper CoFe (123 Oe) and lower CoFe (160 Oe). Moreover, excellent thermal stability of exchange-bias field of AFC-SUL was also confirmed, demonstrating its potential for the applications of double-layered perpendicular recording media.

HITPERM soft-magnetic underlayers for perpendicular thin film media

A class of nanocrystalline alloys, HITPERM (Fe, Co)–M–B–Cu (M=Zr,Hf,Nb, etc.) found to exhibit excellent soft-magnetic properties is being studied for use as a soft-magnetic underlayer for perpendicular recording media. Previously, we reported that HITPERM films of ∼100 nm thickness sputtered at room temperature (RT) and at ∼2.3 W/cm2 power density had exhibited an amorphous microstructure, which had turned mixed nanocrystalline when prepared at ∼250 °C. However, nanoparticles of FeCo have now been crystallized even at RT without the application of heat, by increasing the sputtering power density to ∼4.5 W/cm2. This dramatically improved the 4πMs while still maintaining a low coercivity. There was a further slight increase in the 4πMs at ∼6.8 W/cm2. Moreover, these soft-magnetic properties were maintained even when the substrate temperature was subsequently raised to ∼250 °C. Transmission electron microscopy studies showed the presence of relatively small nanocrystals of the ferromagnetic α′-FeCo (or α-FeCo) phase alone, for both sets of films. Previously, we had reported that the CoCrPt magnetic layer grew with a strong (00⋅2) texture on amorphous HITPERM. We have now seen that with a thin Ti intermediate layer (∼5 nm) the CoCrPt layer maintained a strong (00⋅2) texture even on the nanocrystalline HITPERM. Thus, due to their particular nanocrystalline nature, these HITPERM films exhibit much better soft-magnetic properties, while still leading to strong (00⋅2) texture on the CoCrPt magnetic layer.

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.

Exchange-coupled CoZrNb/CoSm underlayer for perpendicular recording media

The characteristics and effects of an exchange-coupled CoZrNb/CoSm underlayer for perpendicular recording media are reviewed. A CoSm layer pins CoZrNb domains via exchange coupling resulting from large induced radial anisotropy of the CoSm layer in the disk medium as well as in the CoZrNb layer. The number of CoZrNb domain walls is considerably reduced by the CoSm pinning effect which is effective in both signal stabilization to stray fields and noise reduction. Furthermore, the CoZrNb/CoSm underlayers exhibit high-frequency responses of over 1 GHz in permeability, which also result from their large induced anisotropy. The CoZrNb/CoSm underlayer is expected to enable the practical realization of perpendicular recording in data storage applications requiring high densities and high-speed data rates.

Multilayer films of CoCrTa for perpendicular recording media

Multilayer structures of alternate magnetic and non-magnetic CoCrTa alloys have been prepared in which the magnetic properties can be widely varied by changing the magnetic layer and interlayer thicknesses, In this way, one example has shown that enhanced perpendicular anisotropy can be achieved as demonstrated by an increase in perpendicular coercivity Hc( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\perp</tex> ) and a decrease in longitudinal coercivity Hc(&dlor.). This condition is desirable for application in perpendicular recording media. In addition, a second example has shown that by using much thinner layers (≃15 nm) it is possible to produce a structure in which the magnetization is longitudinal with a very low coereivity of 1.5 Oe. Such soft magnetic films with high Ms and low Hc(&dlor.) can be used as underlayers for perpendicular recording media in order to enhance the efficiency of pole heads.