Kousuke Tobari

Preparation and Characterization of Co/Pd Epitaxial Multilayer Films with Different Orientations

Co/Pd multilayer films were prepared on fcc-Pd underlayers of (001), (111), and (011) orientations hetero-epitaxially grown on MgO single-crystal substrates at room temperature by ultrahigh-vacuum rf magnetron sputtering. The structural and magnetic properties vary depending on the underlayer orientation. A multilayer film consisting of fct-Co(001) and fcc-Pd(001) single-crystal layers is formed on a Pd(001)fcc underlayer, whereas epitaxial multilayer films consisting of Co and Pd layers with fcc(111) and fcc(011) orientations are obtained on Pd(111)fcc and Pd(011)fcc underlayers, respectively. For the film grown on the Pd(001)fcc underlayer, sharp interfaces are formed between the Co and Pd layers. On the other hand, atomic mixing is observed at the Co/Pd interface for the films grown on the Pd(111)fcc and Pd(011)fcc underlayers. The CoPd-alloy layers are formed around these interfaces. The CoPd-alloy formation is enhanced in the order of (001) < (111) < (011). The multilayer films grown on the Pd(111)fcc and Pd(011)fcc underlayers show perpendicular magnetic anisotropies, whereas the film grown on the Pd(001)fcc underlayer is easily magnetized in in-plane directions. The magnetic properties are delicately affected by the crystallographic structures of Co/Pd multilayer films.

Structure and magnetic properties of FePd-alloy epitaxial thin films grown on MgO single-crystal substrates with different orientations

FePd-alloy epitaxialfilms were prepared on MgO substrates of (100) B 1, (110) B 1, and (111) B 1 orientations at a temperature of 600 °C by ultrahigh vacuum rf magnetron sputtering. The structural and the magnetic properties vary depending on the substrate orientation. L10–FePd(001) films are obtained on MgO(100) B 1 substrates, whereas L10–FePd(101) films with the c-axis canted from the perpendicular direction are epitaxially grown on MgO(111) B 1 substrates with six variants. FePd epitaxialfilms consisting of L10(100) and L10(112) crystals are formed on MgO(110) B 1 substrates. A higher long range ordering parameter is obtained on the order of FePd/MgO(100) B 1 > (110) B 1 > (111) B 1. The filmsgrown on MgO(100) B 1 substrates show perpendicular magnetic anisotropy, whereas the filmsgrown on MgO(110) B 1 and MgO(111) B 1 substrates are easily magnetized in in-plane directions. The magnetization properties reflect the magnetocrystalline anisotropies of bulk L10–FePd crystal.

Effect of Magnetic Film Thickness on the Spatial Resolution of Magnetic Force Microscope Tips

Magnetic force microscope (MFM) tips were prepared by coating commercial atomic force microscope (AFM) tips of 5 nm radius with Co and CoCrPt magnetic thin films varying the thickness in a range of 10?80 nm. The structural and the magnetic properties of coated magnetic thin films were investigated by scanning electron microscopy, AFM, X-ray diffraction, and vibrating sample magnetometry. The tip radius and the film surface roughness increase with increasing the film thickness. With increasing the film thickness, the MFM signal sensitivity increases, whereas the resolution decreases due to increase of tip radius. The MFM observation resolutions of 10 nm and 23 nm are obtained with the tips coated with 20-nm-thick Co and 40-nm-thick CoCrPt films, respectively. The MFM resolution is influenced by both the tip radius and the magnetic moment of coated material.

Influence of Temperature and Mechanical Scratch on the Recorded Magnetization Stability of Longitudinal and Perpendicular Recording Media

Stability of recorded magnetization of hard disk drive (HDD) is influenced by external environments, such as temperature and magnetic field. Small scratches are frequently formed on HDD medium surface upon contacts with the magnetic head. The influences of temperature and mechanical scratch on the magnetization structure stability are investigated for longitudinal and perpendicular recording media by using a magnetic force microscope. PMR media remained almost unchanged up to about 300 °C for the area with no scratches, whereas the areas near and under mechanical scratches started to change around 250 °C. The magnetization structure of LMR media started to change at about 100 degrees lower temperature under mechanical scratches when compared with no scratch areas. A quantitative analysis of magnetization structure variation is carried out by measuring the recorded magnetization strength difference estimated from the MFM images observed for a same sample area before and after exposing the sample to different temperatures.