H. Yamane

[001]-oriented nonepitaxial growth in L10-ordered FePt thin film by SiO2 addition and rapid thermal annealing

A highly L10-ordered FePt film with a crystalline [001] orientation was prepared by SiO2 addition and rapid thermal postannealing on an oxidized Si substrate. In order to clarify the mechanism of L10 ordering and the crystalline orientation of a nonepitaxial FePt film, we investigated the effect of the preparation conditions on the film structure. The crystalline quality was strongly dependent on the additive amount of SiO2; a high chemical order without the distribution of the chemical order and a nearly perfect [001] orientation were obtained at a SiO2 composition of 10 vol %. The nucleation of L10 grains with a high chemical order and a [001] orientation was observed from an initial phase transformation stage at a low annealing temperature. The as-deposited FePt–SiO2 film consisted of a nanocrystalline structure in which SiO2 segregated at the grain boundaries; SiO2 diffused with the grain growth during thermal annealing. Because the in-plane tensile stress among the grains was a dominant origin for th...

Structural characterization for L10-ordered FePt films with (001) texture by x-ray diffraction

The nanostructure of L10-ordered FePt films with a [001] orientation prepared by both an epitaxial growth and nonepitaxial method was characterized by fitting X-ray diffraction profiles. Good fitting results for both types of films were obtained by considering the structural inter-and intragrain disorders in a calculation model. The distributions of the long range order and film thicknesses were considered to be part of the structural disorder among the grains. The fluctuation of the lattice spacing and the depth of x-ray interference along the surface normal were also taken into account to explain the structural disorder within the grain. The epitaxial FePt films grown on the MgO(100) underlayer were gradually transformed from a disordered A1 phase to an ordered L10 phase with increasing deposition temperature. A thinner film of 5 nm indicated a relatively low long range order with the fluctuation of lattice spacing. This is attributed to a large mismatch between the lattice of the initial growth layer a...

Fabrication of [001] L10-FePtRh ferro-antiferromagnetic pattern by flat-patterning method

A flat-patterning method that exploits the ferromagnetic (FM) – antiferromagnetic (AF) transition in [001]-oriented L10 FePt1-xRhx films was investigated. FM–AF patterns with dot diameters between 15 and 1000 nm were fabricated by locally diffusing a small percentage of FePt atoms onto the FePt1-xRhx film. The geometric and magnetic properties of the patterns were analyzed in detail. Only the area whose composition crossed the FM–AF threshold underwent a magnetic phase change to the FM phase. FM dots with single-domain structures were observed in the AF matrix in the range of 15–100 nm by magnetic force microscopy.

Study on nanoscale patterning using ferro-antiferromagnetic transition in [001]-oriented L10 FePtRh film

A bit patterning process using the ferromagnetic (FM)-antiferromagnetic (AF) transition in [001]-oriented L10 FePt1-xRhx films was investigated. First, the composition (x) dependence of magnetization (Ms) and magnetocrystalline anisotropy (Ku) of the films was studied. The films with 0 ≤ x ≤ 0.32 showed ferromagnetism (800 ≤ Ms ≤ 1100 emu/cm3) with a high magnetocrystalline anisotropy (1.7 × 107 ≤ Ku ≤ 7.0 × 107 erg/cm3), and the films with 0.34 ≤ x ≤ 0.40 showed antiferromagnetism. The composition of x = 0.34 was the threshold of the FM-AF transition. Next, the FM-AF transition was applied for bit patterning. Atomic diffusion was used for modifying the composition. Only the magnetic phase of the area whose composition crossed the threshold changed abruptly to the FM phase. FM dots with sizes (D) of 20 ≤ D ≤ 1000 nm were observed in the AF matrix by magnetic force microscopy. The dots with D > 100 nm formed multidomain structures, and the dots with D ≤ 100 nm formed a single-domain structure.

Pt/C intermediate layer for Co-Cr perpendicular magnetic recording media with extremely high resolution

In this paper, Pt/C intermediate layer for Co-Cr perpendicular magnetic recording media was investigated. Magnetic and microstructure of the medium were analyzed. The coercivity on the storage layer thickness measured with Kerr effect magnetometer.

Ferromagnetic-Paramagnetic Patterning of FePtRh Films by Fe Ion Implantation

The crystalline and magnetic properties of 6.12 nm thick Fe_x(Pt_0.68Rh_0.32)_100-x films with 50.0 ≤ x ≤ 64.3 and a potential bit-patterning process that utilizes the FM-PM transition caused by Fe ion implantation were investigated. At room temperature, for 50.0 ≤ x ≤ 55.9 the films were ferromagnetic (FM), with an L1₀ phase, whereas for 57.9 ≤ x ≤ 64.3 the films were paramagnetic (PM), with an phase. This composition dependent FM-PM transition forms the basis of a bit-patterning process in which, at first, micro-fabricated resist masks were prepared on the (ferromagnetic) Fe₅₀ (Pt_0.68 Rh_0.32)₅₀ film. Implantation of Fe ions at a dose of 9 × 10¹⁵ ions/cm² then results in an increase of x in the implanted areas, from 50.0 to 58.3. After annealing, 300 nm FM dots were observed by magnetic force microscopy, which confirmed that only the implanted areas had changed from FM to PM and that the dot areas had remained in the FM phase with the L1₀ structure.

Tuning interlayer coupling and domain structure in [Co/Pd]nCo /Ru[Co/Pd(x)]m multilayer by controlling the thickness x of the weak-ferromagnetic Pd layers in the lower Co/Pd multilayer

Interlayer coupling has been studied in a series of perpendicular antiferromagnetically coupled multilayers with asymmetric structures Pd(20 A)/[Pd(15.7 A)/Co(3.6 A)]5/Ru(4.1 A)/Co(3.6 A)/[Pd(x A)/Co(3.6 A)]3/Pd(50 A)/Si substrate. The coupling oscillates between antiferromagnetic and ferromagnetic as a function of x in the bottom sublayers. The strong antiferromagnetic coupling with a maximum value of 2430 Oe, which was determined by the minor-loop shift, was obtained. The pinning direction of the antiferromagnetic coupling also changes with the variation in x. The oscillatory behavior can be attributed to multiple reflections of electron waves at the Co/Pd interfaces and their interference. Micromagnetic structure evolves with a variety of interlayer couplings are observed by magnetic force microscopy. An antiferrostripe domain without a ferromagnetic shift is observed at the as-deposited state. Stray-field induced ferromagnetic domains appear in multilayers with weak antiferromagnetic coupling.

Recording Performance of Perpendicular Recording Media Measured by Contact Type Cusp-Field Write Head

In this paper, recording performance of the CoPtCr-SiO2 media is investigated by using contact-type cusp-field single-pole write head. The relationship between the microstructure of the storage layer and the recording performance is discussed.

Pt/C intermediate layer for Co-Cr perpendicular magnetic recording media with extremely high linear density

Intermediate layers for perpendicular magnetic recording media have been studied for controlling storage layers with fine grains. The magnetic properties of the media was investigated for understanding the effect of the intermediate layer. H/sub c/spl perp// for the medium with the Pt/C intermediate layer showed a little bit large value compared with that with the Pt/Ti one. TEM images of the media were investigated. We show that platinum and carbon layers are suitable intermediate layers for a very fine Co-Cr-Pt-Nb storage layer in double layered perpendicular magnetic recording media.