Hideo Matsuyama

Magnetic Block Array for Patterned Magnetic Media

We have fabricated a magnetic rectangular block array of 130 Gblock/in.2 with a block-size-to-period ratio of 0.85 by using focused ion beam lithography. Each block has perpendicular crystal magnetic anisotropy and a single domain structure. Its advantage as patterned media is discussed in conjunction with thermal stability in recorded magnetization, reading signal, and area density.

Linear and Non-Linear Susceptibilities in Canonical Spin Glass AuFe (1.5 at.%Fe)

Linear, χ 0 , and nonlinear, χ 2 and χ 4 , susceptibilities were measured in metallic spin glass AuFe. Nonlinear susceptibilities for AuFe (1.5 at.%Fe) diverge at T g showing the power law behavior and the critical behaviors around T g are interpreted by Suzukis theory based on Edwards and Anderson model. The critical exponents γ s , δ and β were obtained to be γ s =1.1±0.2, δ=2.0±0.2 and β∼0.9, respectively.

Magnetic domains of permalloy films for magnetic recording thin film heads observed by spin-polarized SEM

The domain structures of cores patterned in thin film heads for disk drive systems were investigated by using spin-polarized SEM. This method made it possible to determine the direction of the magnetization at the domains and domain walls in magnetic cores accurately. Domain structures in the track width, as small as 10 μ m could be observed. Domain structure could also be observed at the tapering area of a thin film head. It was found that the triangular domains without the closure domains are located at the edge of the magnetic core in single- and six-layered permalloy films in some cases. Such a domain structure was regarded as causing the wiggles in the read-out waveforms.

A spin rotator for detecting all three magnetization vector components by spin‐polarized scanning electron microscopy

A spin rotator for observing magnetic domains with all three magnetization components of a sample surface by spin‐polarized scanning electron microscopy (spin SEM) has been developed. The spin rotator is placed between the sample and the spin detector in a spin SEM, and can rotate the polarization vector of secondary electrons by π/2. Although the spin detector itself can detect only two independent polarization components, the rotation of polarization makes third‐component detection possible. The conventional spin rotator, which is a well‐known energy filter named a Wien filter, has been much improved to have a large focusing area by using hyperbolic cylindrical pole pieces as a magnet and several auxiliary electrodes. As a result, all the secondary electrons emitted from the area of a surface as large as 1 mm in diameter can pass the spin rotator with uniform spin rotation, and the distribution of all three magnetization components can be imaged successfully by spin SEM.

Observation of Néel structure walls on the surface of 1.4‐μm‐thick magnetic films using spin‐polarized scanning electron microscopy

Neel‐type surface magnetic wall structure is observed on thick samples such as 1.4‐μm‐thick Permalloy polycrystal film and 1‐μm‐thick Co‐based amorphous films. The structure is observed by using spin‐polarized scanning electron microscopy. These observations are consistent with Hubert’s two‐dimensional domain wall model for thick films [Z. Angew. Phys. 32, 58 (1971)].

A study on thin-film-media noise by magnetic domain observation

Magnetic domain structures of signal-recorded and reverse-DC-erased thin-metal-film media with different signal-recorded noise characteristics have been observed by a spin-polarized scanning electron microscope to determine the noise-generating mechanism. In noisy media, magnetic domains around 10- mu m wide grow at 38 KFCI, and recorded transitions are observed inside them. At the maximum reverse-DC-erase noise condition, which corresponds to the DC demagnetized condition, magnetic domains from 2- to 5- mu m wide are observed. In low-noise media, no large, distinct domains are seen for either condition. The squareness (M/sub r//M/sub s/) of noisy media is 10% higher and the switching field distribution ( Delta h/H/sub r/) is 40% lower than those of low-noise media. The results indicate that large signal-recorded noise is generated from large irregular magnetic domains that grow through strong exchange coupling between crystallites. >

A data acquisition and display system for spin‐polarized scanning electron microscopy (spin SEM)

A new data‐acquisition and display system has been developed for magnetic domain observation using spin‐polarized scanning electron microscopy. The system is composed of 32 frame memories (512×512×16 bit), an image processor with two high‐speed digital signal processors, and a 1280×1024 pixel color monitor. It has the following capabilities: electron probe scanning control; high‐speed (21 s/512×512 pixel image) computing and recording of two components (Px, Py) of secondary‐electron spin polarization; computing and displaying the averaged Px and Py obtained with repetitive scanning; domain image formation for an arbitrary component from (Px,Py) data (8 s/512×512 pixel image); variable speed scanning to obtain a homogeneous quality image in minimum time, even when secondary‐electron intensity varies due to surface inclination; two‐dimensional display of polarization vector distribution; and angle image of the magnetization direction in both black and white and color representation.

High spatial-resolution domain-observation of longitudinal thin film media by spin-polarized scanning electron microscopy

A noise generating mechanism is studied by observing recorded bits of two kinds of high-density recording media, in the 50-140 kFCI range, that produce different levels of noise. The noise power is found to be mainly correlated with the zigzag wavelength of the bit boundary. >

Fine magnetic domain structure of stressed amorphous metal

The fine magnetic domain structure which appears on a stressed amorphous ribbon is studied using a spin‐polarized scanning electron microscope. The detected domain structure differs from any so far reported. The magnetization direction inside the wavy stripelike closure domain fluctuates along the stripes. We propose two possible models to explain this domain structure.

Spin-polarized-SEM observation of surface magnetization across domain wall in permalloy films

Magnetization distribution within the surface layer has been observed for permalloy polycrystalline films using spin-polarized SEM developed recently. In a previous work the authors arrived at a qualitative conclusion that surface structures of 180°, domain wall on permalloy films were Neel type with much larger widths than the one-dimensional estimate for the Bloch type. This conclusion was based on image contrast. However, our closer investigation on quantitative measurement indicates that the surface structure of the wall of 1.4μm thick films is a mixed type, i.e, both Bloch and Neel.