Periodic multilayer thin films of the form (xAl/yNi)n were grown by alternate deposition of pure Al and Ni using dc-magnetron sputtering. The thicknesses of the individual Al and Ni layers are given by x and y, respectively, and the total number of bilayer units is n. For this set of experiments, x was fixed at 3.5 nm while y was systematically varied from 2.4 to 154 nm. The films were tested in as-deposited and annealed states for magnetic properties using a vibrating sample magnetometer and for crystal structure by x-ray diffraction. In both the as-deposited and annealed samples the magnetization per unit volume of Ni declined as the Ni layer thickness decreased. This result can be interpreted in terms of a magnetically ‘dead’ layer at the Al/Ni interfaces. The width of the dead layer increased from 2.9 nm to 5.8 nm on annealing. Magnetic properties were correlated with crystal structure experiments by x-ray diffraction. As-deposited films yielded a Ni(111) texture. The Ni (111) peak decreased in intensity and broadened as the Ni thickness declined. Annealing produced evidence for the growth of the intermetallic NiAl3.

The relationship between crystallographic and magnetic characteristics of multilayered films composed of Fe and MnSb layers were investigated in detail. The thicknesses of Fe and MnSb layers dFe and dMnSb were changed in the range of 50 ˜ 100 and 3˜ 100 Å, respectively. Although only the (110) oriented α-Fe crystallites appeared in the films with dMnSb as small as about 5 Å, both of X-ray diffraction peaks of Fe and MnSb crystallites were not detectable in one with dMnSb of about 15 Å. The growth of both Fe and MnSb crystallites seemed to be strongly prevented in the films with dMnSb in this range. On the contrary, the peaks corresponding to (110)Fe and (110)MnSb appeared in X-ray diffraction diagram for the film with dMnSb above 25 Å. The films with d of 10 Å and dFe of 20 Å exhibite the saturation magnetization 4πMs of 15 kG and the coercivity Hc of 0.2 Oe. Such a low Hc was two order lower than those of both Fe single layer film and MnSb one. This seems to be attributed to the fine granulation of Fe and MnSb crystallites.

Magnetic properties of nanocrystalline alloys produced by crystallization of Fe-Cu-Nb-Si-B amorphous alloys have been investigated. The best result is obtained at the annealing conditions where the main phase is bcc and it is very important to suppress the formation of Fe-B compounds with large magnetocrystalline anisotropy. Homogeneous and ultrafine grain structure has an important effect to improve the magnetic properties. Conclusively, soft magnetic properties of nanocrystalline alloys are related to various factors such as formed phases, ratio of amorphous phase, intrinsic magnetocrystalline anisotropy and magnetic interaction from grain boundary phase.

A proposed cluster model is used to determine analytically the effective magnetic permeability of ferromagnetic percolating systems. It is shown that on the approach to the percolation threshold the real part of the magnetic permeability tends to zero in spite of the increase of ferromagnetic component. This anomaly is due to the formation of large conducting clusters.

4 Co–base amorphous alloys prepared by rapid quenchling are stress–annealed under different temperature (Ta) balow its crytalline temperature Tcry, after pre–annealing. The effect of magnetic anisotropy with Ta shows the mechanism of stress–induced anisotropy is changed from single ionic modal to pair model as Ta inereases. The effect of Mn content may exaggerate the model changing.

Both frequency and field dependencies of the ac magnetic permeability in composite iron films were measured for different thickness of a conducting cell. Attention has been focused on additional dispersion caused by the skin effect. The data obtained are analyzed on the basis of the effective medium approximation.

Thin film couple of NiFe/FeMn has been used in the magnetoresistive read head design in the magnetic recording industry. The strong magnetic coupling between FeMn and NiFe is of most importance in providing the stability of the MR head. FeMn has been shown to grow epitaxially on NiFe surface and form a metastable fcc structure. The existence of this fcc structure is believed to be the source of the magnetic coupling. It has also been shown that the grain to grain epitaxy exists in this polycrystalline thin film couple, however with only indirect evidence such as Moiré fringes across the interface boundary. To further study this pseudomorphic growth phenomenon, a specially prepared large grain FeMn/NiFe thin film couple was used. Lattice imaging of the interfacial structure was obtained by high resolution cross-section transmission electron microscopy. The plan-view TEM imaging and electron dilfraction patterns also show clear evidence of the grain to grain epitaxy in almost all the grains. The epitaxial strain associated with each coupled grain was also evidenced by the isolated strain contours within each grain. Detailed interfacial structure analysis will be given to elucidate the mechanism(s) by which the interfacial strain is accommodated.

The antiferromagnctic FeMn thin film has been used to stabilize the domains in NiFe films by exchange-coupling, thus eliminating the Barkhauscn noise in magnetoresistive sensor designs. T'he strength of this exchange-coupling is highly dependent on the interfacial structure, as well as the interfacial composition of this NiFe/FeMn thin film couple. We have conducted isothermal, as well as isochronal anneals of NiFe/FeMn thin film couples, and monitored their magnetic properties, in particular the strength of their exchange-coupling. The strength of exchange-coupling, measured by the shift of the B-H loop obtained from a hysteresis loop tracer, increased monotonically with annealing time for isothermal anneals between 200 and 300 °C. At higher temperatures (up to 500°C), the interdiffusion between the two layers is so extensive that the NiFe layer loses its sort-magnetic properties and the coupling strength is degraded. Composition depth-profiling by scanning Auger analysis was conducted to study the interdiffusion profiles of the annealed samples. Cross-section transmission electron microscopy (XTEM) was used to study the microstructure, crystallography, and composition of these thin films after annealing. Micro-beam composition analysis was also carried out and the compositional profile obtained was compared to the Auger depth-profile results. Transmitted electron diffraction using selected area electron diffraction (SAED) and elongated probe micro-diffraction (EPMD) of XTEM samples was used to study the crystallography of these films.

Physical origin of high initial permeability, μi, in Fe based films with large magnetocrystalline anisotropy and magnetostriction is systematically discussed in connection with the microstructure of the films. In order to decrease the local anisotropy fluctuation to determine μi in these films, decrease of effective magnetic anisotropy, Ueff, of each grain mainly caused by the sufficient reduction of grain size is required. Induced uniaxial magnetic anisotropy energy, Ku, in film plane plays an important role to decrease Ueff through the micromagnetic interaction. The ratio of Ueff /Ku proposed as the important key to analyse the magnetization process. The dependence of μi Ku is classified concerning for Ueff/Ku.

Sendust is limited in its application due to its brittleness. This paper shows the brittleness of sendust ribbon made by rapid quenching can be improved by microalloying of boron with negligible influence on its magnetic properties. The mechanims of boron effect on its properties is discussed.

The FeAlSi film magnetic anisotropy has been studied in relation to the residual stress and crystalline orientation. Experiments show that the magnetic anisotropy behavior depends on the geometrical location of the substrate with the target during the deposition. The main origin of the magnetic anisotropy is attributable to the magnetoelastic effect due to the residual stress anisotropy, which may be induced by the anisotropic incidence of sputtered particles to the substrate.

Microstructural differences between sendust(FeSiAl) films sputtered in pure Ar atmosphere and FeSiA1N films sputtered in Ar+4%N2 mixture atmosphere were measured using Mössbauer effect. These films were prepared by a conventional RF sputtering method. As a source for the Mössbauer measurement, 57Co was used.

Before annealing, there are no differences between both films in Mössbauer spectra. The both patterns are observed as simple six-line spectra from Fe atoms in a disordered structure. After annealing, both patterns are not simple six-line spectra, which indicate there are more than two types Fe site in the crystal. A tremendous difference between both films appears in the spectra. 95% Fe atoms of FeSiAl film are at the two different sites of D03 structure. However, in FeSiAlN film, only 54& Fe atoms are at the D03 sites and about 30% Fe atoms are at different sites whose hyperfine field is about-250kOe. This value of hyperfine field is expected at a D03-like site with 5 Fe nearest neighbors. This D03-like site is explained as a site that one Fe atom is substituted for one D-site Si or Al atom in a D03 unit cell.

No Fe-nitrides were observed in FeSiAlN films.

Rapidly quenched Nd2Fe14B-based permanent magnets owe their high intrinsic coercivity Hci to their unique submicron-sized grain structure. While no clear consensus has yet emerged regarding the microscopic origin of coercivity in these fascinating materials, magnetic and structural data suggest pinning of magnetic domain walls at or in an intergranular phase between Nd2Fe14B grains as the most likely mechanism. The small, randomly oriented grains in isotropic melt-spun ribbons produce a magnetic structure wherein each Nd2Fe14B grain is a single magnetic domain, with the domain walls expelled to the grain boundaries. The magnetic interaction between neighboring grains plays an important role in the magnetization reversal of individual grains, as revealed, for example, by detailed examination of the initial magnetization and demagnetization processes. The formation of large domain structures via these interactions is frustrated by the random grain orientation in ribbons, but short range magnetic correlations between grains (“interaction domains”) are observed locally.

The oriented grains in aligned die upset magnets produce a very different magnetic structure having large scale coherent domains which extend through many grains. A variety of experiments, including studies of the temperature dependence of Hci, suggest that coercivity arises from pinning of the extended domain walls at Nd2Fe14B grain edges.

The coercivity of melt-spun Pr-Fe-B ribbons was found to increase with the addition of Cu and Al. The change in size and shape of grains with Cu and Al substitution were investigated by transmission eletron microscopy (TEM) and the grain boundary structure was further examined with high resolution electron microscopy (HREM). For small substitutions only “disturbed lattice” regions were observed at most of the grain boundaries. Secondary phases rich in the added elements were observed mostly at tripple grain boundaries and sometimes at grain boundaries in samples with larger amounts of substitution. The grain size in the substituted samples does not decrease much with further substitution. However, the shape of grains changes from polyhexagons to facets. The enhancement in coercivity can be explained by the grain size reduction and the modification of microstructure at the grain boundary regions.

The amorphous-crystalline transformation in R-Fe-B ribbons was studied in situ in a transmission electron microscope (TEM) and with X-ray diffraction. Metastable phases of α-Fe(R) and Fe3B were found to form during crystallization before the final R2Fe14B phase is formed. The Fe3B phase is believed to be important for the formation of the 2:14:1 phase because its “local unit structure” is one of the basic building blocks in the 2:14:1 unit cell.

Brief reviews on corrosion and coercivity mechanisms of sintered Nd-Fe-B magnets are given. Results of recently undertaken transmission electron microscopic study of Nd15 - Fe78-xCoxB7 sintered magnets (x = 3, 6 and 10) are presented. Micro-beam electron diffraction patterns obtained from Nd-Co phases in these magnets could be indexed according only to an orthorhombic cell of Nd3 Co among the binary Nd-Co compounds for x = 3 to 10. Relations of coercivity and magnetizability of this type of magnets to their microstructure are discussed in connection to the effects of V or Mo addition which are to enhance coercivity and to improve magnetizability. It is suggested that a decrease in the local demagnetization effects resulting from a decrease in the width of the grain size distribution due to these-additives is the origin of the enhancement of coercivity and the improvement of magnetizability.

The magnetic hysteresis behavior of crystalline Co50Pt50 films has been studied in samples with thickness in the range of 100-2000 Å. The room temperature coercivities of the as-grown films are of the order of 100 Oe. After annealing at 650°C the coercivities vary between 400 and 4300 Oe with the higher values obtained in thicker specimens. The high coercivities obtained are attributed to the hard magnetic phase CoPt with an ordered fct structure that is formed after annealing. The variaton of coercivity with thickness is examined and related to the crystal structure evolution and to grain size effects.

For type II superconductors (SC), magnetic field can be trapped, or pinned due to persistent internal current. Upon magnetization, SC samples behave in some ways similar to a metallic permanent magnet. The trapped field is high and quasi-persistent, and we refer to it as a “magnet replica”. So far, nearly 1T @ 65 K, and over 0.4 T @ 77 K have been measured within small (about 1 × 1 × 0.6 cm3) melt-textured Yba2Cu3Ox (MT-Y123) samples. Based on our theoretical studies, extrapolation to larger scale magnets indicates that 2–4 Tesla in liquid Nitrogen (and even larger field at lower temperatures) is achievable with our high temperature superconductor (HTS) material. Using this effect, magnets with dipole, quadrupole, or more complicated configurations can be made of existing MT-Y123 material, thus bypassing the need for HTS wires. Two types of motors have been successfully constructed, using the trapped field in MT-Y123 samples.

The spatial distribution of the trapped magnetic field on MT-Y123 materials has been studied. A phenomenological model has been developed to account for the trapped field intensity and profile in HTS samples. General features of magnet replicas by HTS will also be discussed.

We have completed a detailed consideration for dynamics (the processes of remagnetization and linear susceptibility) of a superparamagnetic ensemble. The results were obtained using analytical and numerical solutions of the initial Fokker-Plank equation.

This paper proposes the novel processing technique on the formation of InSb thin film which may not be influenced by the vapor pressure difference between In and Sb. Three layers which are composed of In with 1000 A of thickness, Sb with 5000 A and In with 4000 A are deposited sequentially at room temperature. During post heat treatment of these layers, InSb compound phase begins to form and the outer In layer suppresses the reevaporation of more volatile material, Sb. Since multiple single layers are sequentially evaporated, the problem of the severe vapor pressure difference betweentwoevaporating materialsmaynotcontributetothestoichiometriccomposition which may be the most critical parameter to determine the quality of films. The characterization of a fabricated InSb thin film by X-ray diffraction and scanning electron microscope shows that the proposed multilayer method may be a powerful technique to form a high quality InSb compound thin film.