H. Shoji

Magnetic moment of α″‐Fe16N2 films (invited)

In order to determine the value of the intrinsic magnetic moment of the α ‘ phase, the films of nitrogen‐martensite with various N content were fabricated under various reactive sputtering conditions. The magnetic moment of (α ‘+α’)‐Fe16N2 films is discussed in connection with the change of the unit‐cell volume of the bct structure and the degree of N site ordering in nitrogen‐martensite. As a result, it is found that (1) the same structure as bulk α ‘‐Fe16N2 is realized in the present films, (2) the saturation magnetization σs of the α’ phase increases about 4% with increasing unit‐cell volume of the α’ phase, (3) the degree of N site ordering from α’ to α ‘‐Fe16N2 does not much affect σs, and (4) the experimentally obtained maximum value of σs for the (α ‘+α’)‐Fe16N2 film was 232 emu/g. The intrinsic value of σs in the α ‘ phase (in the perfectly ordered state) is proposed to be no more than 240 emu/g at 300 K.

α″-Fe16N2 problem — giant magnetic moment or not

Abstract We reviewed the present situation of the α″-Fe 16 N 2 problem for α″-Fe 16 N 2 films with and without giant magnetic moment in connection with structure and magnetic moment. The results of XRD and TEM analysis did not show any difference between α″-Fe 16 N 2 films with and without giant magnetic moment. The Mossbauer spectrum was quite different in each case. The hyperfine field of Fe 16 N 2 film synthesized by the present authors splits into three hyperfine field interactions. However for the Fe 16 N 2 with giant magnetic moment, hyperfine field interaction did not split and is almost the same as that of pure α-Fe. Therefore, the interpretation of Mossbauer spectra is the key item to solve the α″-Fe 16 N 2 problem.

Structure and magnetic moment of α″‐Fe16N2 compound films: Effect of Co and H on phase formation (invited)

In order to determine the intrinsic value of magnetic moment, σs, of α″‐Fe16N2 compound, the magnetic moment of (α″+α′)‐Fe16N2 films is discussed in connection with the degree of N site ordering in nitrogen–martensite. To establish the more general relation between Fe–N martensite structure and σs, the Fe–N system is expanded to Fe–Co–N and Fe–H–N systems. As a result, it is found that (1) The existence of completely the same structure as bulk α″ phase was reconfirmed even in the film form by the precise structural analysis using x‐ray diffraction, transmission electron microscopy and Mossbauer analysis, (2) Fe–H martensite was synthesized by using sputtering under Ar+H2 atmosphere, (3) Stable formation of α″‐(Fe100−XCoX)16N2 (X=10–30) phase through N site ordering by postannealing is proposed to be fairly difficult due to the sudden decrement of the phase decomposition temperature, Tp.d., of α′‐(Fe100−XCoX)–N (X=0–30). Tp.d. of α′‐(Fe100−XCoX)–N (X=0–30) phase decreases from 200 °C to RT with increasing ...

Giant magnetic Kerr rotation for Pt substituted MnSb compound films with NiAs type structure

Abstract Magnetic and magneto-optical properties were investigated for Mn-Sb-Pt films with the concentration range of 38 at% λ = 500 nm. From the results of structural analysis and of θ k spectrum, it was found that the giant θ k observed in present experiment arises from the NiAs type MnSb compound including Pt atom.

Structure and magnetic moment of Fe16N2 sputtered film

Abstract The structure analyses of α″−Fe 16 N 2 sputtered films were made by using XRD, TEM, CEM and EPMA. The following results were verified: (1) the lattice constants, a and c , of the α″−Fe 16 N 2 phase in the sputtered film were found to be the same as those of bulk α″−Fe 16 N 2 ; (2) the film consists of highly oriented single-crystal grains with diameter of about 100 A; and (3) the volume fraction of ( α ″ + α ′)-Fe 16 N 2 phase in the annealed film was found to be 71–82%. The value of the saturation magnetization of the α″−Fe 16 N 2 phase was discussed by assuming N site ordering in the α′-martensite. The results revealed that no strong correlation between the N-site ordering in α′-phase and the magnetic moment is found and that the value of the saturation magnetization of the α″−Fe 16 N 2 phase at RT is concluded to be no more than 240 cmu/g.

Giant magnetic Kerr rotation for MnSbPt films with NiAs structure

Magnetic and magneto-optical properties, Kerr rotation angle, Kerr ellipticity and reflectance, were investigated for Pt substituted MnSb compound films with film thickness of about 1000 /spl Aring/ by RF sputtering in the concentration range of 44 at% >

Soft magnetic properties of Fe-N and Fe-Si-N thin films sputtered in (Ar+N/sub 2/) plasma

The soft magnetic properties of sputtered (0 approximately 3-wt%) Si-Fe alloy thin films fabricated in (Ar+N/sub 2/) plasma were investigated in connection with metallurgical structure. 2.7-wt% Si-Fe film annealed at 400 degrees C shows a high effective permeability mu /sub eff/ of about 1600 at 5 MHz. It has been observed that this film consists of alpha -Fe with a grain size of less than 150 AA and a slight expansion of lattice spacing of the

Influence of local anisotropy fluctuation on soft magnetic properties of the sputtered Fe-Si-Al alloy films

Effective permeability, mu /sub eff/, uniaxial anisotropy field, H/sub k/, and local anisotropy fluctuation represented as magnetic ripple, SA/sup -5/8/ (S is the structure constant and A/sup -5/8/ is a coefficient equal to the power of the exchanges stiffness constant), were systematically studied as a function of composition and film thickness for Fe-Si-Al ternary alloy films. The influence of H/sub k/ and SA/sup -5/8/ on mu /sub eff/ is discussed in connection with the film structure. The magnitude of mu /sub eff/ was found to depend strongly on the magnitude of microscopic local anisotropy fluctuation. A decrease of the film thickness caused a marked increment in SA/sup -5/8/ due to the change of the preferred grain orientation from

Grain size reduction by utilizing a very thin CrW seedlayer and dry-etching process in CoCrTaNiPt longitudinal media

To decrease grain size and grain size distribution in CoCr15Ta3.5Ni10Pt5/Cr longitudinal thin film media, a very thin CrW54 seedlayer combined with a dry-etching process were utilized. In the media dry etched after CrW54 deposition, utilization of 1.5 nm CrW54 reduces the grain diameter and σ to 9.4 and 2.2 nm, respectively. By optimizing CrW54 seedlayer thickness and dry-etching process, grain diameter and σ of the magnetic layer can be reduced while maintaining coercivity, longitudinal orientation of magnetic grains, and magnetic interactions.

The dependence of media noise on the magnetic cluster size for Co based thin film media fabricated under ultra clean sputtering process

The media noise performance is discussed quantitatively in connection with magnetic microstructure for Co based thin film media fabricated under Ultra Clean (UC) process. Results are summarized as follows: (1) The media noise decreases by reducing the dispersion of magnetic field strength at transition, (2) The dispersion of magnetic field strength at transition is suppressed by the reduction of magnetic cluster size, and (3) The grain size reduction and the decrement of intergranular magnetic coupling play an important role for the improvement of recording performance though the reduction of magnetic cluster size.