Films For Perpendicular Magnetic Recording Research Articles

FePt-C nanogranular films for perpendicular magnetic recording

We report the study of L10 ordered FePt-C nanogranular perpendicular anisotropy films and a media consisting of an 8 nm thick FePt-C hard magnetic layer covered with a 2 nm thick soft magnetic layer (CoFe and FePt-C). All the films were fabricated on oxidized Si substrates with a (100) textured polycrystalline MgO intermediate layer of 10 nm in thickness. Cosputtering of Fe, Pt, and C on the MgO layer results the formation of L10 ordered FePt nanogranular films with a strong c-axis texture and the average FePt particle size of about 5 nm with a narrow particle size distribution of 1.4 nm in standard deviation. Perpendicular coercivity is controllable between 7 and 12 kOe. The coercivity and the saturation field of the FePt-C granular films can be reduced by 55% and 38%, respectively, with the capping of thin soft magnetic layer. This study demonstrates that the FePt-C system accomplishes suitable nanogranular structures and magnetic properties for ultrahigh-density perpendicular recording media.

Fe–Pt–MgO stacked films for perpendicular magnetic recording

Fe–Pt–MgO stacked storage layer constructed by [Fe–Pt/Fe–Pt–MgO/Fe–Pt] trilayered structure was proposed for a next-generation high-density perpendicular magnetic recording medium. The Fe–Pt–MgO composite middle layer was prepared by sputtering the Fe–Pt–MgO composite-type target including relatively large MgO content of 50 vol%. The Fe–Pt(0 0 1) seed layer deposited on MgO underlayer was effective in forming the ordered fct(0 0 1) phase for the Fe–Pt–MgO composite film. The reduction of transition jitter noise and the suppression of signal overlap were observed in the stacked-type medium with the Fe–Pt–MgO middle layer of 1 nm thickness. The improvement of recording properties is attributed to the pinning effect of magnetic domain wall by the Fe–Pt–MgO composite layer inserted into the middle of pure Fe–Pt storage layer.

Reduction of grain size and intergrain interaction in FePt∕Pt∕Cr trilayer thin films for perpendicular magnetic recording

A FePt single layer, a FePt∕Cr bilayer, and a FePt∕Pt∕Cr trilayer were fabricated. Transmission electron microscope images revealed that the grain size of a FePt single layer was around 50nm, and decreased to 20nm with a Cr underlayer. When a Pt layer was inserted between the FePt magnetic layer and the Cr underlayer, L10 FePt(001) thin films with perpendicular magnetic properties can be obtained with a grain size of around 20nm determined primarily by the Cr underlayer. The intergranular interactions determined from the Kelly-Henkel plot were the exchange coupling between magnetic grains in the FePt single layer. In contrast, negative values of the δM curve were obtained for the FePt∕Cr bilayer and the FePt∕Pt∕Cr trilayer, implying the presence of dipole interactions in both films. Smaller grains and the negative δM of FePt∕Cr were derived from the diffusion of Cr into the FePt layer.

Pulse-Reverse Electrodeposited Nanograinsized CoNiP Thin Films and Microarrays for MEMS Actuators

This paper reports on a low residual stress hard magnetic CoNiP alloy electrodeposition technique for microelectromechanical systems (MEMS) applications based on techniques previously developed for CoNiP thin films for perpendicular magnetic recording. Besides electrolyte chemicals, various processing parameters including applied current density, film thickness, electrolyte agitation, electrolyte pH, and temperature are optimized to provide thick films with low residual stress. The resulting hard magnetic CoNiP alloy exhibits a relatively high perpendicular coercivity of around and a high saturation magnetization of . Thick films up to with a low residual stress have been realized using this CoNiP electrodeposition technique. In addition, CoNiP microarrays thick are surface micromachined for the integrations with magnetic MEMS devices. Experimental results confirm that these microarray configurations have a higher coercivity and maximum magnetic energy density, , than thin films in the perpendicular direction.

Investigation of the crystallographic texture and interface roughness on CoCrPt /Ti magnetic thin films

The structure and interface of Co74Cr16Pt10 (40 nm thick)/Ti (10 nm thick) films for perpendicular magnetic recording were studied using x-ray scattering and transmission electron microscopy. Improved out-of-plane coercivity and squareness resulted from the combined effects of higher crystallinity and better texture of the CoCrPt (002) film, and increased interface roughness. The relationship of sputtering pressure to the structural effects is discussed.

Nanostructured L1<SUB>0</SUB> Fe-Pt Based Thin Films for Perpendicular Magnetic Recording

Aiming at development of ultra-high density magnetic recording media, nanostructured Fe–Pt perpendicular recording media were tailored. In order to obtain a crystal orientation of Fe–Pt(001) for a double-layered perpendicular medium with a soft-magnetic underlayer, a heteroepitaxial layer configuration was applied. A high pressure sputter-deposition method was effective for lowering the fct-ordering temperature of the L10 crystal structure. Microstructures of the media were constructed by two kinds of methods, i.e. inducing crystal defects and forming composite films with oxides. The highest SN ratio was obtained by a wall pinning type medium with the induced crystal defects. Design and possibility of the Fe–Pt(001) media were discussed.

Compensation for the demagnetizing field in remanence measurements of perpendicular magnetic recording films

It is necessary to compensate for the demagnetizing field in remanence measurements of perpendicular magnetic recording films.In this paper,a new method of compensating for the demagnetizing field is proposed and an effective reverse field Heff is used to evaluate the dc demagnetization remanence curves,isothermal remanent magnetization curves,and the ΔM plots for perpendicular magnetic recording films.The demagnetization factor N is important for this method,and three methods are used to estimate the value of N. The results of the ΔM plots indicate that the intergranular interactions in Ba ferrite films seem to be of exchange coupling,while those in Co-Cr-Ta films are of magnetostatic interactions.

A structural study of effects of NiP seed layer on the magnetic properties of CoCrPt/Ti/NiP perpendicular magnetic films

The CoCrPt/Ti/NiP films for perpendicular magnetic recording were studied using X-ray scattering and anomalous X-ray scattering. When the NiP seed layer was used, the long range order of the texture peak of the magnetic film decreased and less Co was associated with this Bragg order. The structural results were consistent with the observed increased coercivity and decreased magnetization due to the increased magnetic grain isolation caused by the presence of NiP seed layer.

Fluctuation field and time dependence of magnetization in TbFeCo amorphous rare earth-transition metal thin films for perpendicular magnetic recording

In this work we report on the experimental analysis of the time decay of magnetization in the films of amorphous TbFeCo alloys for perpendicular magnetic recording. It is shown that the experimental results can be explained on the basis of the thermally activated incoherent subnetwork magnetization reversal model. Thermally activated reversal of the transition metal subnetwork and associated reversal of the antiferromagnetically coupled rare-earth subnetwork may result in effective stabilization of the net film magnetization. Experimentally obtained activation diameter value Da∼5–6 nm corresponds to the exchange length or the domain wall width in the films under study. The small activation diameter value combined with high stability factor k∼250 mean that the TbFeCo amorphous film should be capable of supporting a thermally stable perpendicular recording at over 100 Gbit/in2 recording density.

The effect of Pd buffer layers on magnetic exchange energy of Co/Pd multilayered films for perpendicular magnetic recording

A Co/Pd multilayered film is one of the promising perpendicular magnetic recording (PMR) media with high magnetic squareness, due to interfacial magnetic anisotropy energy. However, the lack of a magnetic decoupling factor in the Co/Pd film, unlike a compositionally decoupled CoCr based alloy film, possesses large magnetic exchange energy which results in large magnetic domain sizes and high noise source. In this research, we investigate a domain isolation parameter ( α) to control the magnetic exchange energy and domain sizes in terms of the deposition pressures of a Co/Pd recording multilayer and a Pd buffer layer in a PMR disk. The high pressure in the Pd buffer layer is effective to isolate and reduce the Co/Pd domain sizes with a low α value. The observations with a magnetic force microscope (MFM) and a cross sectional transmission electron microscope (TEM) prove that the physically decoupling effect originated from the surface roughness of the Pd buffer layer, plays a major role in creating a fine domain pattern in the Co/Pd multilayer. The dynamic read/write performances of the Co/Pd multilayered disk by a merged giant magneto resistive (GMR) head show that the low α value disk with magnetically decoupled grains has a low medium noise level, compared with the high α value disk.

Compensation for the Demagnetizing Field in Remanence Measurements of Perpendicular Magnetic Recording Films.

Remanence measurements are very useful for estimating the characteristics of intergranular magnetic interactions in recording layers. However, it is necessary to compensate for the demagnetizing field in remanence measurements of perpendicular magnetic recording films. In this study, a new method of compensating for the demagnetizing field is proposed and an effective reverse field Heff is used to evaluate the dc demagnetization measurements, isothermal remanent magnetization measurements, and ΔM for perpendicular magnetic recording films.

Medium noise properties of Co/Pd multilayer films for perpendicular magnetic recording

Co/Pd multilayer media showing different medium noise properties were investigated through the observations of the recorded patterns using a magnetic force microscopy (MFM). For the Co/Pd multilayer medium sputter-deposited at 1 Pa, no reversed magnetic domains were observed between transitions, while the transitions were quite irregular, suggesting a transition noise in this medium. On the other hand, for the Co/Pd multilayer media prepared with an evaporation-deposition method, although locally reversed magnetic domains were observed, the transition lines were straight. Thus, the medium noise in this case appeared to be a white noise caused by the locally reversed magnetic domains between the transitions. Patterns of signals only up to 200 kFRPI were observed for the Co/Pd multilayer medium sputter-deposited at 1 Pa, which exhibited a strong magnetic exchange interaction. However, a signal of 400 kFRPI was recognized for the Co/Pd multilayer medium with a reduced magnetic exchange interaction, which was prepared by evaporation-deposition with the introduction of a small amount of air.

Magnetic and noise properties of Nb added Co–Cr perpendicular medium

Nb addition to Co–Cr perpendicular magnetic recording films has been investigated. Co 74–Cr 22–Nb 4 films exhibited high H c⊥ values surpassing a Co–Cr binary system and satisfied a guiding scheme for a low-noise medium. It was found that the domain size of the film as well as SQ ⊥ was an important factor determining medium noise and that the domain size should be smaller to realize a lower medium noise and a higher resolution. MFM observation revealed that high-density recording up to 400 kFRPI and 17 Gbit/in 2 could be achieved for the Co 74–Cr 22–Nb 4 system.

Effect of Heat-Treatment on the Magnetic Properties and Microstructure of Electroless-Plated CoNiP Films for Perpendicular Magnetic Recording

The effect of heat treatment on the magnetic properties and microstructure of electroless plated CoNiP films for use as perpendicular magnetic recording media was investigated, in order to clarify the film microstructure in the as deposited state, as well as to evaluate their thermal stability. The as-deposited film consisted of a mixture of ≪002≫ perpendicularly oriented hep structure, and fcc structure without any obvious crystal orientation. Heat treatment at temperatures above 400°C changed the dominant crystal structure from hep to fcc. The crystallites grow larger with heat treatment, causing a sharp change in magnetic properties. These changes were due to the disappearance of the magnetocrystalline anisotropy induced by the cobalt hep structure, and the decrease in the shape magnetic anisotropy due to the change in film topology. On the basis of these results, it is suggested that a compositional inhomogeneity due to the segregation of Co-rich regions exists in the as-deposited films; this segregation disappears with heat treatment at higher temperature, so that the crystal structure of the film changes to an fcc structure.

Magnetic texture in films with perpendicular anistropy

The notion of magnetic texture in films for perpendicular magnetic recording is introduced. The characteristics of magnetic texture dispersion ( δϑ 50) in CoCr films are also defined. The method of determination of material constants from the curves of film magnetization, including the first and second anisotropy constants K 1 and K 2, as well as ° ϑ 50 is proposed. The effects of film structure have been studied on the basis of a magnetostatic model of a columnar structure. The shape anisotropy constants is estimated to have the value ≈5×10 5 erg/cm 3, when M s in the volume of column is 400 G. The criteria for the applicability of films as perpendicular magnetic recording media are also formulated.

Microstructure of electroless Co alloy films for perpendicular magnetic recording

The mechanism of columnar crystallite orientation in electroless Co-Ni-Mn-P films for perpendicular magnetic recording media was investigated using SEM, TEM and other methods. Micro-region analysis revealed that the Ni and P in the film is mainly distributed in the grain boundary. So it is suggested that the film has a segregated microstructure. The segregation of Ni-P alloy is the main cause which makes the c axis of alpha -Co orient along the film normal and the columnar grain become fine. Magnetic measurements also showed that the films had a good perpendicular property.

Nuclear magnetic resonance study of Co-CoO films for perpendicular magnetic recording (abstract)

Co-CoO films, which are evaporated in the atmosphere of a small amount of O2, have large perpendicular magnetic anisotropy and show excellent read-write (R-W) characteristics. With heat treatment, the microstructure of a film changed and the R-W characteristics were further improved.1,2 This result indicates that the microstructure of a film changed and the R-W characteristics were further improved.1,2 This result indicates that the microstructure of a film closely relates with the R-W characteristics as it does so for Co-Cr films. We measured the spin-echo spectra of a film having various magnetizations to investigate the relationships between R-W characteristics and film microstructure, because NMR is very sensitive to the slight changes of film microstructure.1 A strong absorption was observed at 223 MHz which is for α-Co. The intensity decreased drastically as the amount of oxygen in the films increased and very broad satellites appeared around 250 MHz, implying that Co atoms having a larger magnetic moment than that of α-Co exist for the films containing oxygen atoms. Further, heat treatment increased the absorption intensity at 223 MHz, which means that the internal stress or the lattice defects were removed. The R-W characteristics were found to relate with the absorption intensity. This result shows that the crystallinity of a film greatly influences the R-W characteristics of Co-CoO films.

7336. Study of CoCr films for perpendicular magnetic recording using nuclear magnetic resonance: K Yoshida et al, J Appl Phys, 68, 1990, 705–712

7336. Study of CoCr films for perpendicular magnetic recording using nuclear magnetic resonance: K Yoshida et al, J Appl Phys, 68, 1990, 705–712

Magnetization Process in Perpendicular Magnetic Recording Films with Columnar Structure

Magnetization Process in Perpendicular Magnetic Recording Films with Columnar Structure

Electroless Cobalt Alloy Perpendicular Anisotropy Films Plated from a Simplified Malonate Bath

The electroless-plated Co alloy films for perpendicular magnetic recording were prepared from a newly developed plating bath with simplified composition, and their magnetic and structural properties were investigated. The composition of the films changed with varying cobalt sulfate concentration in the plating bath. The films containing 10-30 at% of Co in deposits, which show high crystallinity and crystal orientation, have perpendicular magnetic anisotropy. Among them, the Co-24 at% film shows the largest perpendicular magnetic anisotropy. The film consists of hcp crystallites whose <002> axis orients perpendicular to the film plane, showing high crystallinity and the crystal orientation from the initial deposition stage with a thickness of 20 nm. It was confirmed that the films for the use of highly functional devices can be fabricated from the electroless-plating bath with simplified composition.