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Effects of stress and strain in FePt thin film on $L 1_{0}$ ordering are investigated by employing single-crystal substrate of which lattice mismatch with FePt crystal is varied in a range from −10.3% to +0.8% for 10 nm thick FePt thin film. Thin films are prepared under different conditions; direct deposition at 600 °C, two-step process consisting of 200 °C deposition followed by 600 °C annealing, and the two-step process with MgO cap layer formed on top of the FePt layer at 200 °C. Formation of $L 1_{0}$ -FePt(001) crystal and $L 1_{0}$ ordering is enhanced on a substrate with larger negative lattice mismatch, though the lattice mismatch with substrate is decreased greatly by introduction of misfit dislocation and by lattice bending in FePt material. The lateral in-plane strain in FePt material associated with several factors: substrate material, film morphology, and cap layer has given a strong influence in $L 1_{0}$ -ordered phase formation in FePt thin film.

Er17(Co1− x Cu x )83 (at. %, $x = 0-1$ ) alloy thin films are prepared at 500 °C by employing Cr(211) underlayers hetero-epitaxially grown on MgO(110) substrates. Crystallographic phase formation is influenced by the Cu/Co composition. Amorphous film is formed for $x = 0$ , whereas epitaxial films are obtained for $x = 0.25-1$ . Cu atom addition into Er–Co film promotes crystallization. The films with $x = 0.25-0.5$ consist of a mixture of Er(Co,Cu)5 $(1\bar {1}00)$ and Er(Co,Cu)5(0001) crystals. The crystallographic orientation relationships are Er(Co,Cu)5 $(1\bar {1}00)[\bar {1}\bar {1}20]~\vert \vert $ Cr(211) $[\bar {1}11], (211)[1\bar {1}\bar {1}]$ and Er(Co,Cu)5 $(0001)[\bar {1}\bar {1}20]~\vert \vert ~\text {Cr}(211)[\bar {1}11], (211)[1\bar {1}\bar {1}]$ . However, with further increasing $x$ value, the crystallographic phase changes to a phase different from Er(Co,Cu)5. Control of the amount of Cu atom is important to stabilize the Er(Co,Cu)5 phase.

FePt alloy films of 2 to 10 nm thicknesses are prepared on (001) single-crystal underlayers of MgO, VN, and VC by employing a two-step method consisting of low-temperature deposition at 200 °C followed by high-temperature annealing at 600 °C. MgO, VN, and VC crystals are selected as underlayer materials, since the crystals have the same NaCl-type crystal structure and similar lattice constants of about 0.42 nm but different surface energies. The single-crystal underlayers are prepared by RF sputtering on the single-crystal substrates of MgO and SrTiO3 at 600 °C. The influences of underlayer material and FePt film thickness on the $L1_{0}$ ordering degree, the magnetic properties, and the surface morphology are systematically investigated. Epitaxial films involving $L1_{0}$ (001) crystal structure with the $c$ -axis normal to the substrate surface are formed on all the underlayers. As the film thickness decreases, the ratio of out-of-plane to in-plane lattice constant $c/a$ decreases and the ordering degree $S$ increases. Stronger perpendicular magnetic anisotropy is observed for an FePt film with a higher $S$ value. The film thickness trends of $c/a$ , $S$ , and magnetic properties are similar to those for FePt films thicker than 5 nm formed on MgO underlayers. However, when the thickness is decreased to 2 nm, de-wetting of deposited atoms occurs on MgO underlayers during annealing at 600 °C. The surfaces of 2-nm-thick films formed on MgO underlayers are composed of isolated islands. On the contrary, continuous surfaces are realized for the investigated film thickness range of 2–10 nm in the cases of VC and VN underlayers. The surface roughness of FePt film formed on VN underlayer ( $R_{a}$ : 0.1–0.2 nm) is lower than that of film formed on VC underlayer ( $R_{a}$ : 0.1–0.4 nm). This paper shows that the employment of a VN underlayer is effective in the preparation of $L1_{0}$ ordered FePt ultra-thin film with flat surface.

Magnetic force microscope (MFM) tips are prepared by coating silicon tips of 4 nm radius with 20-nm-thick metallic magnetic films with and without 2-nm-thick oxidation protection layers. Iron (Fe) is used as the magnetic material, whereas carbon (C), silicon nitride (Si-N), or silicon carbide (Si-C) is employed as the protection layer. The MFM tips are exposed in an environment of high temperature of 70 °C and high relative humidity of nearly 100%. The effect of protection layer on the spatial resolution is investigated as a function of period of exposure to the environment. The resolution of MFM tip without protection layer deteriorates from 7.2 to 21.2 nm in 10 days. The deterioration is attributed to an increase in the tip radius and a loss of the detection sensitivity caused by oxidation of coated Fe material. In contrast, the resolutions of tips with C, Si-N, and Si-C layers are kept almost constant at 12.1 ± 0.5, 12.1 ± 0.5, and 14.8 ± 2.1 nm for a time span of 10 days, respectively. The coating of a very thin protection layer has been shown effective in keeping the MFM tip performance for a long period of time by preventing the oxidation of coated metallic magnetic material.

Fe, Co, and Ni thin films are deposited on GaAs(110) substrates at room temperature using a radio frequency magnetron sputtering system. The film thickness is varied in a range between 1 and 40 nm. The growth behavior and the detailed resulting film structure are investigated by reflection high-energy electron diffraction and pole-figure X-ray diffraction. The bcc single-crystals nucleate on the substrates for all the film materials, though the bcc structure is metastable for Co and Ni materials. The metastable structure is stabilized through heteroepitaxial growth. The crystallographic orientation relationship is bcc(110)[001]||GaAs(110)[001]. With increasing the thickness beyond 2 nm, the bcc-Co and bcc-Ni crystals start to transform into fcc structure through atomic displacements parallel to the slide planes of bcc( $10\bar 1$ ), bcc( $01\bar 1$ ), bcc(011), and bcc(101) that are 60° inclined from the surface. The Co and Ni films thicker than 2 nm involve fcc crystals. On the contrary, Fe films possess bcc structure for all the thicknesses.

L1 0 films formed on (001)-oriented underlayers or substrates may involve (100) crystal with the c-axis lying in the film plane in addition to (001) crystal with the c-axis normal to the film surface. In this paper, FePt, CoPt, and FePd alloy films with L1 0 structure are prepared on MgO(001) single-crystal substrates. The c-axis orientation is accurately controlled to be perpendicular by introducing a thin MgO cap layer on magnetic films with disordered structure prepared by low-temperature deposition at 200 °C and by annealing the bilayer films at 600 °C. The phase transformation preferentially occurs along the perpendicular direction in the MgO/(FePt, CoPt, FePd)/MgO sandwich structures. Furthermore, the cap layer promotes L1 0 ordering. The order degrees of FePt, CoPt, and FePd films with and without cap layers, (S w/ , S w/o ), are (0.82, 0.58), (0.36, 0.30), and (0.72, 0.62), respectively. The FePt film with cap layer shows a strong perpendicular magnetic anisotropy and a very low in-plane coercivity because of which the film does not include L1 0 (100) crystal and possesses a high-order degree.

Fe, Fe 94 Si 6 , Fe 98 C 2 , and Fe 95 B 5 (at. %) single-crystal thin films of bcc(001) orientation are prepared on MgO(001) substrates using an ultrahigh-vacuum magnetron sputtering system. The influence of magnetic anisotropy on the magnetostriction under rotating magnetic field is investigated. Fe, Fe 94 Si 6 , and Fe 98 C 2 films show four-fold symmetries in in-plane magnetic anisotropy, where easy and hard magnetization directions are, respectively, observed along bcc[100] and bcc[110]. Higher saturation fields measured along bcc[110] are recognized in the order of Fe (6 kOe) > Fe 98 C 2 (5 kOe) > Fe 94 Si 6 (4 kOe). Triangle output waveforms of magnetostriction appear when these films are measured under low-rotating fields. The behavior is related with the motion of 90° magnetic domain walls in magnetically unsaturated film. With increasing the rotating field, the films approach to magnetic saturations and the waveform gradually shifts to usual sinusoidal shape. Larger threshold rotating field is observed in the order of Fe > Fe 98 C 2 > Fe 94 Si 6 , which is related to the saturation field. On the contrary, Fe 95 B 5 film possesses an almost isotropic property in in-plane measurement and shows sinusoidal waveforms even when the film is magnetically unsaturated. The waveform is affected by the symmetry and the strength of magnetic anisotropy.

Co x Pt 100-x (at. %) alloy epitaxial films with the close-packed plane parallel to the substrate surface are prepared on MgO(111) substrates heated at 300 °C by varying the Co content of x from 0 to 100. The stacking sequence of close-packed plane (the volume ratios of fcc and hcp crystals, V fcc and V hcp ) and the order degree are quantitatively determined. The films with Pt-rich and nearly equiatomic compositions primarily consist of fcc crystals (V fcc >0.9). With increasing the x value beyond 56, the V hcp value drastically increases. The films with Co-rich compositions consist of mixtures of hcp (V hcp ≈0.8) and fcc (V fcc ≈ 0.2) crystals. The films with 31 ≤x≤ 86 involve metastable ordered phases. The order degree of S L11 ,Bh is kept constant around 0.25 in a compositional range of 31 × 75. From the viewpoints of volume ratios of fcc and hcp crystals and order degree, the crystal structure is determined to vary A1 A1 + SFs (SFs: stacking faults) L1 1 + SFs ⇒L1 1 + Bh (+D0 19 ) ⇒A3 + SFs with increasing the x value. The films including ordered phases show strong perpendicular magnetic anisotropies. It is shown that the uniaxial magnetocrystalline anisotropy energy of Co x Pt 100-x film can be kept >10 7 erg/cm 3 while controlling the saturation magnetization from 600 to 1150 emu/cm 3 .

The magnetic properties of epitaxial Fe(001) films, prepared on GaAs(001) substrates by RF magnetron sputtering, were investigated by ferromagnetic resonance spectroscopy operating at Q-band (35 GHz). The in-plane angle dependence of the resonance fields showed four-fold magnetic anisotropy with an easy (hard) direction along [100] ([110]). The anisotropy constant was slightly smaller than the magnetocrystalline anisotropy constant of bulk Fe. Ferromagnetic resonance linewidths, caused by the magnetic damping of Fe films, were narrow (

Co epitaxial thin films were prepared on single-crystal MgO substrates of (100), (110), and (111) planes heated at 300degC by ultra high vacuum molecular beam epitaxy. The film crystal structure varies depending on the substrate orientation. On MgO(100) substrate, a Co(112macr0) epitaxial bi-crystalline film with an hcp structure is obtained. A Co(110) single-crystal film with an fcc structure is formed on MgO(110) substrate, whereas a Co(0001) single-crystal film with an hcp structure is grown on MgO(111) substrate. Co film growth on MgO substrates follows the Volmer-Weber mode. The in-plane magnetization properties reflect the magnetocrystalline anisotropy of bulk hcp-Co or fcc-Co crystal. The Gilbert's damping constants of these 40-nm-thick epitaxial Co films are determined.

Angular dependence of Gilbert's damping constant alpha for Ni-Fe(001) single-crystal thin films were investigated by employing Q-band (35 GHz) and X-band (9 GHz) ferromagnetic resonance analysis in terms of the specimen's crystal structure. The alpha for 10-nm-thick specimen had constant values of 0.006, which were estimated by the Q-band ferromagnetic resonance (FMR) spectra, when the spectra were measured with changing external field directions in the film plane and out of plane. The alpha for the Ni-Fe specimens did not depend on the crystal directions. The alpha values estimated by X-band FMR spectra were in good agreement with those by Q-band FMR spectra, when the magnetization of the specimens was saturated at the X-band resonance field. The alpha values were overestimated, when the magnetization was not saturated and the specimens had multidomain structures at the resonance field.

FePd alloy films of 1 to 500 nm thicknesses are prepared on MgO(001) single-crystal substrates by employing a two-step method consisting of low-temperature deposition at 200 °C followed by high-temperature annealing at 600 °C. The influences of film thickness on the crystallographic orientation, the degree of L 10 ordering, the magnetic property, and the surface roughness are systematically investigated. FePd(001) single-crystal films with disordered structure grow epitaxially on the substrates at 200 °C. The in-plane lattice is expanded to accommodate the lattice misfit between the film and the substrate (−9%). The distortion is decreased with increasing the thickness. When the films are annealed at 600 °C, transformation to L 10 phase occurs. The films thinner than 40 nm consist of L 10(001) variant with the c-axis normal to the substrate surface, where the transformation along the perpendicular direction is preferentially taking place. On the contrary, the films thicker than 100 nm involve L 10(100) and L 10(010) variants whose c-axes lie in the film plane and are rotated around the film normal by 90° of each other. The volume ratio of L 10(001) variant decreases to 0.22, as the thickness increases up to 500 nm. The order degrees of films thinner than 40 nm are 0.6–0.7. With further increasing the thickness, the order degree decreases. The lattice deformation in the disordered FePd film before annealing is effective in enhancing L 10 ordering and aligning the c-axis perpendicular to the substrate surface. The easy magnetization direction varies from perpendicular to in-plane, as the thickness increases from 100 to 500 nm. The magnetic anisotropy is affected by the crystal orientation and the order degree. The films thinner than 2 nm have island-like surfaces, where condensation of deposited atoms on substrate is taking place during the annealing process. When the thickness is increased beyond 10 nm, a flat surface is kept before and after annealing.

Compositional and temperature dependencies of saturation magnetization (M/sub s/) and uniaxial magnetocrystalline anisotropy (K/sub u/) are determined using single crystal CoCr-alloy thin films. Temperature dependencies of M/sub s/ and K/sub u/ are stronger with increasing Cr content. M/sub s/(OK) and Curie temperature (T/sub c/) decrease linearly with increasing Cr content in a Co-Cr-X (X=Ta, Pt) system. M/sub s/(OK) and T/sub c/ become zero at the Cr concentration of 33 at.%, Co-Cr-Pt specimens have higher T/sub c/ and higher K/sub u/ than those of Co-Cr-Ta specimens with similar Cr concentration. The magnetic properties of polycrystalline medium are confirmed to depend strongly on those of Co-rich core crystalline grains in Cr segregated microstructure.

Recording and signal decay characteristics of perpendicular CoCr-alloy thin film media are investigated in comparison with those of longitudinal media. A perpendicular medium shows recording resolution 25-32% higher than that of a longitudinal medium with similar low density output. The medium S/N of a 25 nm thick perpendicular medium is comparable to that of a 16 nm thick CoCrPt longitudinal medium at high linear densities. The signal decay rate of the high Mr/Ms perpendicular medium is below 0.2% per decade of time for all linear densities. These results and thermal stability considerations based on the temperature dependence of KuV/kT indicate that CoCr-alloy perpendicular recording media are promising to extend the linear density well beyond 400 kFCI.

Gilbert's damping constants, alpha, of Ni-Fe and Ni-Co thin films are determined by Q-band ferromagnetic resonance (FMR) analysis. alpha is calculated from the resonance width of the FMR spectrum. alpha of Ni85 Fe15 film is found to be 0.0034, which is one-fourth of those of Ni film (alpha=0.013) and Co (alpha=0.013). alpha of the Ni100-x Cox specimens increases with decreasing the Co concentration from 100 to 68 at%, and the alpha value of Ni32 Co68 film has the maximum value of 0.0021. The alpha values of the Ni-Co specimens are nearly the same as those of the Co-Cr-Ta and the Co-Cr-Pt

Magnetic properties are investigated for Co-Cr-Pt thin films deposited on nonmagnetic h.c.p.-Co(Cr,Ru) underlayers with different h.c.p. lattice constants. Higher coercivity, higher coercive squareness, and lower fluctuation field are observed when the h.c.p. lattice constant is close to that of the Co-Cr-Pt recording layer. Temperature dependence of magnetic properties indicates that employment of nonmagnetic Co-Cr-Ru layer is effective to increase the coercivity and to enhance the thermal stability of recording layer.

Developments of magnetic head, recording medium, positioning, and signal processing technologies made it possible to perform magnetic recording at an areal density of 2 Gb/in/sup 2/ on a prototype 3.5-in diameter hard disk drive. A track density of 17 kTPI, which is comparable to or even greater than that used in optical storage systems, is used to minimize the reduction in the physical clearance between the medium and the head. The authors outline the system and its component technologies. The read/write characteristics of the 3.5-in prototype disk system are also reported. >

An analytical magnetic force microscopy has been applied to investigate the relationship between the media S/N and the microscopic magnetization irregularities of CoCr-alloy longitudinal and single-layer perpendicular media recorded at linear densities up to 450 kFCL. When the S/N is compared between longitudinal and perpendicular media, a 16-nm-thick CoCrPt longitudinal medium shows a little higher S/N than that of a heat-treated 25-nm-thick CoCrTa perpendicular medium. The medium S/N is found to deteriorate with increasing the size and the number of magnetization transition irregularity.

The magnetic anisotropy K/sub u/ value of Co/sub 81/Cr/sub 15/Ta/sub 4/ polycrystalline thin film medium was determined by using the 45 degree magneto-torque and the rotational hysteresis methods and compared with those of Co-Cr-Ta single crystal films with different Cr contents. The anisotropy field H/sub k/ of polycrystalline specimen determined by the rotational hysteresis method is confirmed to be underestimated. The K/sub u/ of the Co-Cr-Ta polycrystalline film determined by using the 45 degree magneto-torque method showed a reasonable agreement with that estimated from the single crystal specimen by taking into account of the Cr segregation in the polycrystalline grains.

The composition and temperature dependencies of uniaxial magnetocrystalline anisotropy constants K/sub u1/ and K/sub u2/ are investigated by torque magnetometry for (1010)-oriented Co/sub 96-x/Cr/sub x/Ta/sub 4/ single crystal thin films (x=8-19 at.%). The K/sub u1/ and the Ku/sub u2/ values of Co/sub 88/Cr/sub 8/Ta/sub 4/ are determined at 290 K to be 2.2/spl times/10/sup 6/ and 5.9/spl times/10/sup 5/ erg/cm3, 6.9/spl times/10/sup 5/ and 5.3/spl times/10/sup 4/ erg/cm/sup 3/, respectively, with increasing Cr concentration from 8 to 19 at.%. When the temperature is increased from 290 to 450 K, K/sub u1/ of Co/sub 88/Cr/sub 8/Ta/sub 4/ thin films decreases by 27% to 1.6/spl times/10/sup 6/ erg/cm/sup 3/. The temperature dependencies of K/sub u1/ and K/sub u2/ increase with increasing Cr content in Co-Cr-Ta films. The compositional and the temperature dependencies of K/sub u1/ and K/sub u2/ are related to the decrease in Curie temperature of Co-Cr-Ta material with increasing Cr concentration.

Influences of seedlayer on surface and cross-sectional film structures are investigated for the magnetic recording media fabricated on a plastic disk substrate. An irregular film growth is observed when a recording medium consisting of C/Co-Cr-Pt/Cr-Ti multilayer is deposited directly on an amorphous polyolefin substrate. Zr or Ti seedlayer with HCP crystal structure is found to be useful in improving the film microstructure and is comparable to that formed on a glass substrate. The recording media with Zr or Ti seedlayer have desirable microstructure and surface flatness which are necessary for high density magnetic recording applications.

An epitaxial thin film growth has been applied to prepare bicrystalline CoCrPt longitudinal recording medium using an MgO(100) single crystal disk substrate. X-ray and TEM measurements have revealed that the magnetic layer has a bicrystalline structure which consists of two variant domains with their c-axes lying in-plane and perpendicular-to each other. The maximum medium coercivity is observed at (2n+1)/spl pi//4, while the minimum coercivity is observed at n/spl pi//2 from the MgO[010] when measured along the circumferential direction. The highest signal to noise ratio, the highest linear resolution, and the best off-track performance are observed at (2n+1)/spl pi//4 where the direction of the recording magnetic head field lies between the easy magnetization axes of the two variant domains. >