T. Wakiyama

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.

Magnetocrystalline anisotropy for Sm2(Co-Mn)17 compound with TbCu7 type disordered structure

Abstract Magnetocrystalline anisotropy for Sm2(Co1−xMnx)17 (0≤x≤0.26) compound with metastable TbCu7 type disordered structure, whose Sm3+-ion configuration is different from that of ordered stable Th2Zn17 type structure, was systematically examined and discussed by means of a single ion method. Kul for TbCu7 type disordered structure was found to be 1.2–1.4 times as large as that for Th2Zn17 type structure. The increase of Kul with change in crystal structure from Th2Zn17 to TbCu7 type is caused by the increase of Sm3+ single ion anisotropy resulting from the change of Sm3+-ion configuration.

Magnetocrystalline Anisotropy of Co and Co-Ni Alloys

The magnetocrystalline anisotropy constants K u1 and K u2 of Co–Ni alloys containing Ni up to 30% were measured at temperatures between 77 K and 700 K by means of a torque magnetometer. For the alloys containing Ni less than about 7%, the sign of K u1 was found to change from positive to negative in the h.c.p. phase. The temperature at which K u1 becomes zero was found to increase from 510 K for Co to 620 K for 5% Ni–Co alloy. The temperature dependences of K u1 and K u2 are discussed on the basis of the theory developed by Zener and Carr. It is clarified that the temperature dependences of K u1 and K u2 cannot be explained by the power law of the reduced magnetization. The contributions of the magnetoelastic coupling energy to K u1 and K u2 are discussed. The obtained value of Δ K u2 for Co is one-tenth or one-hundredth as small as the value of K u2 .

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.

Magnetization, Curie temperature and perpendicular magnetic anisotropy of evaporated Co-rare earth amorphous alloy films

Abstract Magnetization, Curie temperature and perpendicular magnetic anisotropy have been investigated for Fe100-xRx (R=Pr, Nd, Sm, Gd, Dy, Er) amorphous alloy films prepared by evaporation method. It is found that the Curie temperature of these films is much lower than that of amorphous alloys prepared by rapid quenching technique. The reason may be a difference of compositional short range ordering owing to the different sample preparation. The dependence of perpendicular magnetic anisotropy on temperature and composition is discussed based on one ion magnetic anisotropy of rare earth ions. The main part of the perpendicular magnetic anisotropy can be considered due to the large one ion magnetic anisotropy of rare earths.

Superconducting and Structural Properties of the New Ba1-xLnxCuO3-y Compound System (Ln=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er and Yb)

The Ba1-xLnxCuO3-y compounds (Ln=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er and Yb) with x=0.34 and (Ln=Nd, Sm and Eu) with x=0.2, 0.4 and 0.5 were prepared. A superconducting transition between 75 and 93 K was observed magnetically in the compounds (Ln=Nd, Sm, Eu, Ho and Er) with x=0.34. X-ray studies showed that most compounds with high Tc have the oxygen-defect perovskite structure.

Magnetocrystalline anisotropy and magnetostriction of Fe-Si-Al (Sendust) single crystals

Abstract The magnetocrystalline anisotropy constant, K 1 and the magnetostriction constants, λ 100 and λ 111 for the Sendust alloys were determined at 300 K in the composition region, 7.5–11.0 wt%Si, 4.0–7.0 wt%Al, bal. Fe. The line of K 1 = 0 in the Fe-Si-Al alloy system was found to lie around 7.0–9.5 wt%Si, 5.5 wt%Al, bal.Fe and 9.5 wt%Si, 5.5–7.0 wt%Al bal.Fe compositions. The line of λ s = 0 was also determined as a function of Fe, Si and Al contents. Both lines of K 1 = 0 and λ s = 0 intersect at the composition, 9.6 wt%Si, 5.5 wt%Al, bal.Fe. This alloy composition is close to those for alloys with high initial and maximum permeabilities. The line of K 1 = 0 determined by the present experiment is found to be different from that of Zaimovsky and Selissky. The line of λ s = 0 is similar to their results.

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