Osamu Kohmoto

Magnetic properties of zero magnetostrictive amorphous Fe‐Co‐Si‐B alloys

The metalloid content dependence of zero magnetostrictive composition of an amorphous (FexCo1−x)100−y(Si0.4B0.6)y alloy in an as‐quenched state is experimentally determined. The iron content (x) of the zero magnetostrictive composition was found to decrease with an increase in the metalloid content (y). The Curie temperature and saturation magnetization decrease with an increase in the metalloid content, while crystallization temperature increases. With an increase in the saturation magnetization of the present alloys the coercive force increases as Hc∝M3s.

Amorphous FeCoNi‐SiB alloys having zero magnetostriction

Zero magnetostriction compositions in the (FeaCo1−a−bNib)100−y(Si0.4B0. 6)y system in the range 20⩽y⩽30 and 0⩽b⩽0.6, the resultant magnetic properties, and the crystallization temperatures were systematically studied as functions of Ni content (b) and metalloid content ( y). The iron content (a=0.058−0.11) decreases with increasing metalloid content ( y), increases with Ni content (b), and then decreases with the addition of Ni. The effects of annealing on low‐field magnetic properties were studied for two kinds of alloys; a high‐Bs alloy and a high‐μ alloy. For the high‐Bs alloy, the effect of sample shape was also studied. The high remanence observed for a tape‐wound toroid and the low remanence observed for a ring‐laminated toroid in the as‐quenched state are attributed to weak uniaxial anisotropy, whose origin may be due to local tension as well as atomic and impurity arrangement introduced during the quenching. By annealing at Tc

High‐field magnetization curves of amorphous alloys

Effects of Si addition into amorphous (Fe0.064Co0.936)76.5 ‐B23.5 alloy having zero magnetostriction were investigated by the measurement of high‐field magnetization at room temperature in the field range 150≤H≤13 000 Oe. The FeCo‐B alloy shows anomalies in both the law of approach to saturation and the para process. The magnetization curve of the FeCo‐B alloy was found to be composed of an atypical 1/H1/2 term as well as an ordinary 1/H term and a para process H1/2 term. The 1/H1/2 dependence is observed in the field range 150≤H≤2000 Oe, and the contribution of para process H1/2 term is large in the high‐field region (H>2000 Oe). With small addition of Si into the FeCo‐B alloy, however, the 1/H1/2 term becomes negligible and the 1/H term increases due to changing defect structure. It was also found that, with the Si addition, the spin wave stiffness constant increases, whereas the saturation magnetization tends to decrease. The Si addition causes a change in amorphous microstructure influencing short‐ran...

Ferromagnetic Resonance in Epitaxial Fe Films on MgO

Ferromagnetic resonance measurements were carried out to study the magnetic anisotropy and the crystallographical orientation in epitaxial (001) Fe films grown on (001) MgO. The magnetocrystalline anisotropy field (2K1/M) and the saturation magnetization (4πM) were measured by the angular dependence of the resonance field; the static field was applied in the film plane and the vertical plane. The obtained 2K1/M and 4πM values are close to those of bulk Fe. Therefore, these results suggested that the specimen was a single crystal; the orientation was [100] Fe//[110] MgO.

Mossbauer Effect of Fe-Cu-Nb-Si-B Alloys Having High Permeability

Mossbauer spectra of finely crystallized Fe73.5Cu1Nb3Si13.5B9 alloys, produced by annealing their precursory rapidly quenched alloys, have been studied. The spectrum of the alloy annealed at 550°C consists of at least four composites of six absorption peaks. The hyperfine fields are obtained as 304, 275, 235, and 180 kOe. It is assumed that the Fe atoms have at least four kinds of local environments: ordered Fe3Si(I)-like, ordered Fe3Si(II)-like, α-Fe-like, and Fe2B-like and/or amorphous Fe3B-like environments.

Characterization of Damaged Layer Using AC Surface Photovoltagein Silicon Wafers

Ferromagnetic resonance in 1000-A-thick Co films evaporated on sapphire, glass or MgO substrates has been studied. An effective uniaxial anisotropy field (Hk) of -16.27 kOe and gyromagnetic ratio (γ/2π) of 3.10 GHz/kOe were obtained for Co film on sapphire. Assuming the saturation magnetization (4πM) of 17.58 kG, we derived a small intrinsic perpendicular anisotropy field (Hk+4πM) of 1.31 kOe.

Magnetic Properties of Rapidly Quenched Nd10Fe85-xTxB5 (T=Zr, Nb) Alloys

Magnetic properties were studied for Nd10Fe85-xTxB5(T=Zr, Nb; x=0, 4) alloys, which were first rapidly quenched and then crystallized by heat treatment. An energy product of (BH)max=12.2 MGOe, coercive force of iHc=9.2 kOe, and remanence of Br=8.2 kG were achieved in a Nd10Fe81Zr4B5 alloy; the Nd content is the lowest ever reported for a Nd–Fe–B alloy having a high-energy product.

Hard magnetic properties of sputtered Co and Co-P films

Abstract Both magnetic properties and microstructure of sputtered Co and Co-4.8 wt% P films ( ≈ 3000 A) deposited near room temperature are studied as a function of Ar pressure P Ar ranging from 4×10 -3 to 1.4×10 -1 Torr. The coercive force H c of the film is a strong function of P Ar . The coercive force of Co increases from 25 to 270 Oe with increasing P Ar . With an addition of phosphorus in Co, H c increases substantially. At high P Ar ( ≈ 1×10 -1 Torr), a high H c of 700 Oe and a low squareness of 0.58 are obtained. From observation of the microstructure, it is concluded that the structure of columns is responsible for the high H c and the low squareness.

High Coercive Force of Substituted SrFe12-aMaO19 (M=Al, Cr) Ferrite Particles

The effects of the substitution of Al or Cr into Sr-ferrite powder on the Curie temperature (Tc), saturation magnetization (σs) and coercive force (Hc) were studied for SrFe12-aMaO19 (M=Al, Cr; a=3, 4, 5). With increasing substitution content, both Tc and σs decrease, while Hc increases drastically. We obtained a high Hc of 13.0kOe for SrO5.8Fe7/6Al5/6O3.

Effective Demagnetizing Factors in Ferromagnetic-Resonance Kittel Equation

Simple equations of effective demagnetizing factors Nxe and Nye for use in Kittels ferromagnetic resonance (FMR) formula have been derived for the first time. The effective demagnetizing factors are derived from anisotropy energy (G) and a static field direction expressed by a spherical coordinate system (θ,). Using the equations, the resonance equation at every direction can be easily calculated without the need for crystal-axis rotation. Compared with Macdonalds derivation, our derivation is simple.