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Current concepts of the physical origin and mechanisms of losses in magnetic materials are reviewed under three traditional categories: hysteresis losses, eddy-current or dielectric losses, and residual losses. The phenomenological Landan-Lifshitz equation is used to quantitatively express the various manifestations of the residual losses. Possible physical mechanisms contributing to the phenomenologically introduced Landau-Lifshitz damping term are qualitatively discussed.

A simple, fast method of characterization of anisotropic magnetic materials uses a nonreciprocal X-band rectangular cell. The material may be a solid, powder, or magnetic liquid. A network analyzer measures the scattering parameters, and an original numerical processing routine computes the permeability tensor components. Two anisotropic magnetic materials have been characterized: a ferrofluid made with magnetite particles suspended in an hydrocarbon and a barium iron oxide powder. The knowledge of permeability behavior of magnetic liquids is important in designing specific nonreciprocal microwave devices. Experimental results are in good agreement with the proposed theoretical simulated model. Index Terms - Inverse problems, magnetic anisotropy, magnetic liquids, magnetic microwave devices, nonreciprocal wave propagation, permeability measurement, rectangular waveguides.

Fe-based amorphous alloys in Fe- (Al, Ga)-(P,B,C, Si) system were found to exhibit a wide supercooled liquid region exceeding 50 K before crystallization. The high stability of the supercooled liquid enabled the production of cylindrical bulk amorphous alloys with diameters up to 2 mm by copper mold casting. The Fe-based bulk amorphous alloys exhibit ferromagnetism with the Curie temperature of about 600 K. The saturation magnetization (Bs), coercivity (Hc) and permeability ([[micro].sub.c]) at 1 kHz in as-quenched state are 1.07 T, 12.7 A/m and 3600, respectively, for [Fe.sub.73][Al.sub.5][Ga.sub.2][P.sub.11][C.sub.5][B.sub.4] and 1.14 T, 0.5 A/m and 3200, respectively for [Fe.sub.71][Al.sub.5][Ga.sub.2][P.sub.10][C.sub.6][B.sub.4][Si.sub.1]. Besides, the use of the Fe-based amorphous alloys enabled the production of thick amorphous ribbons above 100 [[micro]meter] in thickness and the thick samples also exhibit good soft magnetic properties. The success of synthesizing the bulk Fe-based amorphous alloys with good soft magnetic properties is promising for future development as a new type of soft magnetic materials.

Some typical examples of large magnetoresistance effects observed in intermetallic compounds are reviewed and briefly compared with the giant magnetoresistance (GMR) of magnetic multilayers. Basically, the large magnetoresistance changes are observed at metamagnetic transitions in two classes of intermetallics, antiferromagnets and spin fluctuators. In the former case, a metamagnetic-transition is connected with the suppression of the antiferromagnetic coupling between magnetic moments as discussed with several examples of f-electron materials (Nd[Ga.sub.2], UNiGa and other UTX antiferromagnets). The latter class is represented by the R[Co.sub.2] compounds in which a large resistivity drop is connected with the formation and ferromagnetic ordering of Co magnetic moments, which leads to the suppression of the spin fluctuation scattering of conduction electrons. In FeRh based alloys we observe combination of both phenomena, the suppression of antiferromagnetic coupling in the Fe sublattice and the formation of Rh moments. The possibilities of tuning the material parameters desired for applications are discussed with several examples of Sm[Mn.sub.2][Ge.sub.2], Ce[(Fe, T).sub.2], Ce[(Fe, X).sub.2], [(Mn, T).sub.2]Sb and MnPtAl.

A micromagnetic theory is presented for spin-reorientation transitions in ultrathin magnetic films with normal surface anisotropy. Both discrete and continuum models are investigated and coincidence is found between the results derived from them. Two continuous transitions in spin orientation, from uniform and normal to canting, and then to uniform and in-plane, are observed as the film thickness is increased. The effects of higher-order terms in the expansions of the anisotropies compared to the dominant terms are also considered. A method for evaluating the surface anisotropy is formulated. The relation between the present micromagnetic theory and the phenomenological theory is discussed.

Switching properties of a regular square lattice of 40x40x3 [[[micro]meter].sup.3] highly uniaxial, single domain magnetic garnet pixels have been measured magnetooptically. 'Up' and 'down' switching fields, coercivities and interaction fields were measured on an assembly of hundreds of particles. Statistical analysis of the data shows the relationship between major loop parameters and mean values of the distributions. Local demagnetizing tensor elements were calculated for the non-ellipsoidal geometry and the interaction fields from different neighbors were computed. The importance of the effect of the geometry, shape and size of particles on the switching properties is demonstrated. The agreement with experimental values is very good. The simplicity of this model system is attractive for studying artificially structured 2-D arrays of small particles.

A solid-state phase transformation (SSPT) is observed in nanocrystalline [Sm.sub.2][Fe.sub.17][C.sub.x], x=0-1 ([Th.sub.2][Zn.sub.17]-type carbides) prepared by both ball milling and rapid solidification. Upon annealing at 800 [degrees] C the [Sm.sub.2][Fe.sub.14]C ([Nd.sub.2][Fe.sub.14]B-type) phase is formed for x [greater than or equal to] 0.3. For x between 0.3 and 1.0, the [Sm.sub.2][Fe.sub.17][C.sub.y] (y [similar to] 0.3) and [Sm.sub.2][Fe.sub.14]C phases co-exist. The process of the SSPT to [Sm.sub.2][Fe.sub.14] is faster in finer-grain samples. The annealing time required for a complete transformation varies from 15 min for a sample with an average grain size of 40 nm to 28 h for a 200 nm grain size sample. These results suggest that the SSPT is made accessible by reducing the grain sizes. Studies on [Nd.sub.2][Fe.sub.17][C.sub.1.0] show that certain [Nd.sub.2][Fe.sub.14]C powders synthesized through SSPT contain highly anisotropic particles, suggesting a promising technique to produce anisotropic [Nd.sub.2][Fe.sub.14]B-type permanent magnets.

We discuss, in terms of 1D and 2D micromagnetic models, the basic characteristics of the demagnetization mechanisms acting in hard magnetic materials. This includes the study of the hysteretic and relaxational processes and, particularly, the investigation of the temperature dependence of coercivity. From our results we conclude that, even in highly anisotropic materials, demagnetization should be described in terms of nucleation and propagation of finite magnetic moment structures of the domain wall type.

The use of single crystal bulk and film iron garnets in optical sensors is reviewed. Magneto-optic sensitivity and its stability are important parameters that depend on a variety of factors, including optical design. Polarimetric and diffractive sensor technologies are summarized, and several recent demonstrations of magnetic field, current, and rotation sensing using garnets are described. Garnets also find application as important nonsensing components in sensor systems.

The Magnetic Force Microscopy (MFM) technique is demonstrated to provide quantitative information on not only micromagnetics but also on recording performance. A novel method is introduced for analyzing MFM images of recorded bit patterns to determine recording parameters such as signal and signal-to-noise ratio. The results are compared with those measured by a read head. Both signal and signal-to-noise ratio are found to be higher in the CoCrTaPt/CrMo medium than in CoCrTa/Cr medium for linear densities greater than 150 kfci. Recorded patterns can be observed in CoCrTaPt for linear densities up to 370 kfci while the patterns in CoCrTa start to deteriorate for densities higher than 250 kfci. Better high density performance of CoCrTaPt results from the finer structure of an isolated recorded transition which is attributed to reduced magnetostatic and exchange intergranular interactions. The direct overwrite patterns for CoCrTaPt exhibit narrower erase bands and less interactions between the old and new data; the overwrite at 232 kfci is 28dB.

This experimental study separates the hysteresis, eddy current, and electromechanical motion losses of a soft magnetic material for electric power energy conversion applications. Mechanical responses of the magnetic material to sine and square wave voltage excitation are compared. Commercially-available, METGLAS 2605S3-A tape cores were evaluated up to 300 C for sine wave and square wave voltage excitation frequencies 1-100 kHz. Data presented illustrates the effects of maximum flux density, frequency, waveshape, and temperature on the specific core loss and size and shape of the B-H loops. Relative losses play a major role in material selection for electronic and electric power applications including power converters, transformers, controllers, and filter elements. Dynamic measurements of the magnetostrictive response of these specific toroidal test cores were made using a sensitive, capacitive probe and a unique application of frequency modulation. The dynamic behavior of the toroidal test cores and the related unusual B-H loop characteristics were compared to results obtained by an electromechanical model.

Wear resistance of Fe-N based micrograin and other soft magnetic thin films was measured using commercial 8mm VCR and tapes. Fe-Ta-N and Fe-Al-N films which contain ceramics phase such as Ta-N show a high Vickers hardness, but their wear resistance was not the highest one. Fe-Ru-Ga-Si and Fe-Al-V-Nb-O-N films showed low wear loss when they were rubbed by ME tapes. Corrosion properties were estimated by measuring the quantity of Fe dissolved into salt water after dipping a surface lapped thin film specimen. Nitrogen showed a remarkable effect in reducing the corrosion of Fe-N films. Cu was found to be an attractive additional element to increase the corrosion resistance without decreasing magnetic properties for Fe-Al-V-Nb-O-N films.

A soft-phase based heterostructure magnet has been analyzed with micromagnetics. Calculated energy product critically depends on the diameter of the inner soft-phase. The volume fraction of the hard-phase shell region providing the high coercivity is much less than the inner soft-phase region. It was proven, at least theoretically, the energy product of 70 MGOe can easily be achieved for the 100 [angstrom] diameter of soft-phase materials.

We have developed a permanent magnetic pavement marking tape. Sections of varying width and magnetization wavelength were installed in a 230-m linear array. Magnetic field profiles were determined at lateral displacements from the tape out to 0.9 m. Calculations based on a surface pole model with no adjustable parameters gave excellent agreement with the experimental results.

A magnetization process of FeCoSiB amorphous wire under the ac circumferential magnetic field with a triangular waveform is investigated. We obtained the locus chart of the magnetization vector under circular magnetic field, [h.sub.[Theta]]. By increasing the time differential component of [h.sub.[Theta]], d[h.sub.[Theta]]/dt, the hysteresis becomes noticeable gradually. It is believed that an eddy current damping is responsible for this phenomenon.

The aim of this study was to assess the basic magnetic properties of a mixture composed of a commercial lubricant and soft magnetic iron particles, where the particle content is significantly higher than in conventional magnetic fluids, due to the fact that the particles verge on the sedimentation level. This so called magnetic slurry can, then, be regarded as a highly ductile magnetic conducting material for tentative use in magnetic circuit that can change shape under operation. The high particle content results in high saturation field densities that extend the application field towards electric power engineering. This paper, therefore, focuses on properties like relative permeability, losses, the Q-factor and the efficiency for the power frequencies 50 and 400 Hz. It shows that the relative permeabilities are low (below 10). The values of the efficiency and the Q-factor decrease considerably above 0.5 T. That limits the application of the studied slurry in electric power engineering. In such applications, the powder properties must be improved.

Application-oriented characterizations were carried out for [Sm.sub.2][(Co,Fe,Cu,Zr).sub.17] permanent magnets in which both high temperature effects and aging effect are taken into account. Experimental results indicate that application-oriented characterization may provide data more application-oriented than traditional high temperature aging test data. The irreversible loss of the maximum energy product of [Sm.sub.2][(Co,Fe,Cu,Zr).sub.17] caused from thermal demagnetization increases rapidly with temperature. It should be possible to reduce this loss by optimizing magnet compositions and heat treatments, which would significantly improve the high temperature performance of [Sm.sub.2][(Co,Fe,Cu,Zr).sub.17] magnets.

In this paper we report some results on the dependence of the pulsed voltage output on the applied torsion or tensile stress in [Fe.sub.77.5][Si.sub.77.5][B.sub.15] amorphous wires used as magnetostrictive delay lines. The obtained results show a not monotonic dependence of the response of the delay line on applied torsion. For applied tensile stress the response could be fitted by a linear curve for as-cast wires and by an exponential curve for annealed wires. The good ratio between minimum and maximum magnetostrictive delay line signals and the absence of hysteresis suggest the possibility to use this technique in load cells and torque sensors.

Dependence of magnetization dynamics and magneto-impedance effect in positively magnetostrictive [Fe.sub.77.5][Si.sub.7.5][B.sub.15] amorphous wires on annealing conditions was studied. The observed MI ratio of the annealed samples was as much as 36% and the optimum annealing conditions were suggested. The locus of magnetization vector of the annealed wire indicated that the circumferential magnetization was easily proceeded in the annealed wire. It was also suggested that the effect of oxidation should be considered for the samples annealed in air.

Core losses of an 18.5 kW asynchronous motor were measured and computed, by means of a suitable electromagnetic fields package, improved for core loss calculation. The results show that a 1 to 3 % improvement in efficiency is possible by replacing the conventional soft laminations by new materials. The differences between measurement and computation are mainly attributed to rotating fields inside the stator.

Using high performance soluble imide polymer as a binder, it was possible to accomplish a substantial mechanical strength in iron particle cores molded under uniaxial compacting pressure which was much lower than that was commonly applied by others in the past. The directional ordering of oblate spheroidal iron particles occurred despite the low compacting pressure resulting in strong anisotropy in the magnetic properties and mechanical strength in the fabricated cores. The low molding pressure, however, resulted in a low density of core which, in turn, caused the low permeability.

In the paper the iron loss change, due to the modulation technique, in soft magnetic materials, supplied by single phase PWM (Pulse Width Modulated) inverters, is analyzed. Experimental tests on non oriented, oriented and amorphous materials are reported. The specific iron losses vs the flux density, for the two modulation techniques which are practically used in industrial converters, are presented for each analysed material.

Amorphous metallic [Fe.sub.78][Si.sub.9][B.sub.13] fibers, 50 [[micro]meter] in diameter, produced by the melt extraction method, have been studied in the as-quenched state and after furnace annealing at 455 [degrees] C and 480 [degrees] C for times between 0.5 min and 50 min. Measurements of the M-H loops and field dependence of Young's modulus have shown that they behave in a way very like that of amorphous wires. The minimum coercivity of 3 A/m is greater than that found in wires, and the minimum Young's modulus ([approximately]0.45 times the saturation value) is greater. It is suggested that the core-shell domain model applies in the as-quenched state and that stress relief followed by surface crystallization dominate the anisotropy.

In order to synthesize separately the residual amorphous phase present in rapidly quenched nanocrystalline FeSiCuNbB ribbons, powders of nominal composition [Fe.sub.92-x][Nb.sub.8][B.sub.x] with x = 19...45 as well as [Fe.sub.63][Nb.sub.9][B.sub.28] and [Fe.sub.55][Nb.sub.12][B.sub.33] were mechanically alloyed for amorphization and annealed at 540 [degrees] C for structural relaxation. The amorphous powder products show crystallization temperatures [T.sub.x1] and [T.sub.x2] increasing with B content from 600 to 750 [degrees] C and 750 to 950 [degrees] C, respectively. The Curie temperature and also room-temperature saturation polarization show maximum values of about 140 [degrees] C and 0.8 T at a B content of 25 at.%. Compared to that, the Curie temperature of the amorphous grain boundary phase of same composition in nanocrystalline FeSiCuNbB is by at least 100 [degrees] C higher, presumably caused by exchange-field penetration from the adjacent [Alpha]-FeSi nanocrystallites.

The dependence of the magnetic properties of amorphous wire on the diameter have been investigated. The anisotropy constant, hence the internal stress, of the wire increases with the wire diameter. The size of the pinned reverse domain at the wire end increases with the wire diameter. Domain observation shows that irrespective of the change in the wire diameter, the domain structure basically consists of chevron domain layer sandwiched between the surface maze domain and the inner core domain.

Results on the magnetic behavior and properties of negative and nearly zero magnetostrictive amorphous glass-covered magnetic wires and on their changes determined by glass removal, applied tensile stresses, and annealing are reported. The experimental data allow the explanation of their specific magnetic behavior as emerging from the changes produced in the domain structure by these factors. The similarity in behavior between negative and nearly zero magnetostrictive glass-covered wires is due to the very high values of internal stresses induced during preparation.

Reversal of the circular direction of magnetization in a thin wall conical member having a circumferential easy axis is shown to proceed by the axial translation of a single 180 [degrees] domain wall. The entire cone is first remanently magnetized in one circular direction by a large enough coaxial current. An oppositely polarized circumferential domain is nucleated at the small end of the cone when the circular field from a reverse current reaches a critical amplitude. Radial expansion of this critical field with increasing current extends the reverse domain towards the large end of the cone. The field arising from small axial components of magnetization resulting from applied torsion allows ready detection of the axial position of the 180 [degrees] wall.

A two-dimensional model for the coercivity mechanism of [Sm.sub.2][(Co, Fe, Cu, Zr).sub.17] magnets is proposed. The high coercivities of fully heat-treated magnets (> 20 kA/cm) result from pinning sites which are formed by the intersections of the Zr-rich platelet phase (Z-phase) and the Cu-rich Sm[Co.sub.5] (1/5) boundary phase. The pinning strength of this site is assumed to be a result of the large difference between the domain wall energies of the 1/5 phase and the Z-phase. The domain wall energies of almost single phase samples of the Z-phase have been determined by magnetic measurements and by quantitative analysis of domain patterns. The small domain wall energy of the Z-phase of 4 - 11 mJ/[m.sup.2] supports the presented model.

Magnetic materials exhibiting gigantic magnetostriction, especially Terfenol, are currently being widely used in fine positioning and active vibration damping devices. By involving accurate magnetostriction models during design stages, precision of such devices may be significantly enhanced. In this paper a straight-forward approach that employs anisotropic vector Preisach-type hysteresis models in simulating field-stress effects on magnetic materials is presented. Formulation of the proposed model is given and its identification problem is solved. The presented approach has been numerically implemented and numerous digital computer simulations have been performed for Terfenol material. Sample simulation results as well as comparisons with experimentally observed magnetostriction curves are reported in the paper.

A rod of grain oriented Terfenol-D has been subjected to cyclic uniaxial stress of [+ or -]100 MPa about a mean preload of [approximately]120 MPa applied along the grain growth axis. The magnetostrictive strain and d-coefficient measured under uniaxial preload and quasi static magnetic fields are shown to increase after the initial [10.sup.6] cycles of stress. The characterisation of the magnetomechanical behaviour from resonance analyses indicates a slight hardening of the material after -6 x [10.sup.7] cycles and that to regain optimum magnetomechanical coupling, the bias preload and DC bias fields require adjustment in keeping with the effects of the stress cycling. These initial results indicate that magnetostrictive devices constructed from Terfenol-D offer a significant advantage compared with ceramic (PZT) actuators when applied in load bearing situations.

The crystal-field parameters [A.sub.20] and [A.sub.40] were determined from the magnetocrystalline anisotropy constants [K.sub.1] and [K.sub.2] in a linear approximation for [Sm.sub.2][Fe.sub.17][Z.sub.x] (Z = N, C) compounds. For the materials investigated, the values of [K.sub.1] and [K.sub.2] in a temperature range from 4.2 - 533 K have been obtained by a fit of demagnetization curves. The parameters [A.sub.n0] are calculated in two ways: i) from the [K.sub.i] at zero temperature and ii) from the temperature dependence of the [K.sub.i]. Both methods give equivalent results. The value [Mathematical Expression Omitted] has been obtained which corresponds to an inverse THOMAS-FERMI screening length q [approximately equal to] 2.3 [[Angstrom].sup.-1] calculated within the framework of the screened charge model.

Theoretical analysis of weak localization for the three dimensional system presently does not include the case with strong scattering by local magnetic impurities. For paramagnetic [Fe.sub.0.33][Zr.sub.0.67] alloy, a composition just below the ferromagnetic phase boundary, the magnetic impurity scattering tune ([[Tau].sub.s]) is estimated to be comparable to the spin-orbit scattering time ([[Tau].sub.so]), but much less than the magnetic field dephasing time ([[Tau].sub.H]) or inelastic scattering time ([[Tau].sub.i]), so that the magnetic scattering occurs before the magnetic field dephasing does. When the local moments of magnetic impurities (in this case some of the Fe ions) do not interact with each other and their magnetization follows the Brillouin function, the magneto-resistance MR is proportional to [Mathematical Expression Omitted] for small (H/T), where [n.sub.s] is the density of local impurities of moment gS[[Mu].sub.B], and [Delta][Rho](H, T)/[[Rho].sup.2] should be a unique function of (H/T), for a given alloy so long as the impurities are in the Curie regime. Experimental values of the MR at several temperatures for the [Fe.sub.0.33][Zr.sub.0.67] alloy lie on a single curve of [Delta][Rho](H, T)/[[Rho].sup.2] vs. H/T

We have investigated the giant magnetoimpedance (GMI) effect in fibers of different soft magnetic materials and in Permalloy wires. The fibers have been tested in the radio frequency (rf) range, by measuring the voltage drops in different parts of the circuit. The wires have been tested in the ultra high frequency (uhf) range, by measuring the transmission coefficient [s.sub.21] of coaxial lines having as central conductor a HyMu80 wire. The two methods provided quite similar results showing a strong GMI effect for very different magnetic samples.

Samarium cobalt nanoparticles were prepared by ball milling under argon, both with and without a surfactant. X-ray diffraction indicated a single Sm[Co.sub.5] phase, with an average size of 25 nm from Debye-Scherrer analysis of the peak widths, but a broad size distribution based on TEM. SQUID magnetometry yielded the coercivity as a function of temperature between 4 and 300 K. Large coercivities ([H.sub.c] = 2.1 T at 10 K) were observed in the bare particles, but the values were significantly reduced ([H.sub.c] = 0.12 T at 5 K) for those coated with surfactant, indicating probable surface oxidation.

The magnetic properties and structures of Ni and NiFe nanocrystalline films prepared with the gas-deposition method (GDM) are investigated. From the results of STM and SEM, fine particles, approximately 10 nm in diameter, were seen in the films. Furthermore, aggregates several tens of nm in diameter, composed of the small particles, are also observed. The magnetization of the Ni nanocrystalline films is about 50 emu/g, or 90% of that of bulk Ni. Coercivity of the Ni nanocrystals ranged from 4 to 20 Oe. In the case of NiFe, the concentration of Fe is slightly increased as the evaporation temperature is increased.

Ferromagnetic chains consisting of metallic Fe spheres having 20-70 nm diameter have been fabricated by a reduction of ferrous chloride with potassium borohydride. The variations in particle size, boron content and crystallinity with synthesis conditions are investigated. The magnetic properties are examined as a function of annealing temperatures. The observed magnetic properties are correlated to particle size and crystallinity.

Magnetic properties of ultra-thin Fe(100) films are studied experimentally, with an emphasis on the temperature dependence of the magnetization and the influence of the substrate on magnetic properties. It is found that the nature and orientation of the substrate, here Au(100) and Pd(100), have significant effects on the character of the ferromagnetic phase transition, in particular the thermodynamic behavior near the Curie point is strongly dependent on the details of the system, in contrast to the case of bulk Fe. These results are consistent with predictions for the XY model with crystalline anisotropies.

[Fe.sub.x][Ge.sub.100-x] films with compositions in the range 50[less than or equal to]x[less than or equal to]82 at 300K were deposited by rf diode, sequential sputtering from elemental targets. All the films were amorphous at 300K indicating that the Fe concentration in the stable amorphous films was increased by more than 10 at. % over that obtained by vapor deposition. The sequentially sputtered Fe-Ge films exhibited a heteroamorphous morphology with nanoscale features that varied with composition. The variations in the 4[Pi][M.sub.S] and [T.sub.c] for the sputtered Fe rich films, agreed well with data extrapolated from measurements on Ge rich evaporated films. The improvement in the soft magnetic properties produced in these films by rotating magnetic field annealing (RFA) was shown to be correlated with changes in film morphology.

Co-Fe-Si-B films have been prepared using a roll coater and DC magnetron sputtering system onto a polyethylene terephthalate substrate. This thin film exhibited an excellent uniaxial anisotropy introduced by an asymmetric thermal shrinkage of the substrate. Reversal with a single large Barkhausen pulse has been observed in a thin film structure 1mm by 50mm by 0.65 [[micro]meter]. Closure domains have been clearly identified at the film ends. The threshold for the reversal is the coercive force. The reason for reversal with a single Barkhausen jump is that the long narrow film geometry has essentially zero demagnetizing field over most of the film. Once the walls start to move through the center portion of the film, there is nothing to stop them so the reversal proceeds with a single large Barkhausen pulse.

The systematic variations in the magnetic properties of as-deposited (by RF diode sputtering) and annealed [Co.sub.x][Fe.sub.100-x] (x=0, 15, 50, 67, 90, 100) alloy thin films were studied in this work. Maximum values of 4[Pi][M.sub.s] (21.3 kGauss) and [H.sub.c] (253 Oe) were observed in as-deposited films with, respectively, x=15 and x=50. Films with 0[less than or equal to]x[less than or equal to]15 had rotatable hysteresis loops with squareness S[approximately equal to]1. With increasing Co, S decreased and the films became isotropic. Large decreases in [H.sub.c] and resistivity, and large increases in 4[Pi][M.sub.s] were produced in films with x=50 and 67 by annealing in vacuum at 370 [degrees] C, in the presence of an in-planefield. The in-plane anisotropy of the annealed films had a complex biaxial symmetry. A similar biaxial anisotropy was observed in [Co.sub.90][Fe.sub.10] films deposited in an [approximately equal to]200 Oe planar field. This anisotropy was observed independent of whether the substrate was crystalline Si, glass or polyimide. Thus the biaxial anisotropy could not be ascribed to structural constraints at the film-substrate interface, but was probably induced in the film during deposition. The optimum binary CoFe alloy films for application at GHz frequencies require highly oriented uniaxial anisotropies. For reasons not fully understood, it was not possible to obtain well oriented as-deposited, or annealed, binary CoFe films with uniaxial anisotropy.

We examine the low frequency BH loop and complex permeability spectra of multilayer permalloy films laser processed to define samples consisting of stripes perpendicular and parallel to the as-deposited easy axis. For stripes defined perpendicular to the easy axis, it is found for films of thickness [greater than or equal to] 0.745 [[micro]meter] that the demagnetizing field, which is a function of groove depth and stripe width, is able to reorient the easy and hard axes from the initial orientation resulting in a permeability spectra dependent upon groove depth. For relatively thick spacer layers, 45 nm, laser definition of stripes perpendicular to the easy axis induces the different magnetic layers to switch independently. For thinner films the easy and hard axes do not re-orient, but the independent switching of the layers is seen for the thicker spacer layer films. For stripes defined parallel to the easy axis the anisotropy of the sample increases with groove depth, resulting in a decrease in measured permeability.

The effects of [Co.sub.79][Cr.sub.21] undercoats and nucleating layers on the coercive force, anisotropy field, and 5 MHz to 100 MHz complex permeability spectra of magnetically soft, [Ni.sub.81][Fe.sub.19] thin films rf sputtered onto glass substrates are investigated. While very thin layers of hcp oriented [Co.sub.79][Cr.sub.21] [approximately equal to] 5 nm, do not affect the coercive force of the NiFe layer, they do increase the measured anisotropy. Thicker CoCr layers increase both the coercive force and anisotropy field. The 5 nm layers of [Co.sub.79][Cr.sub.21] act to increase the magnitude of the [Mu][prime] spectra, [Mu] = [Mu][prime] - j[Mu][double prime], while decreasing the [Mu][double prime] spectra; thicker layers of CoCr reduce both [Mu][prime] and [Mu][double prime].

The time dependence of the magnetization of pure and Co/Ti-doped Ba ferrite particles is analysed at low temperatures and compared with the dependence at room temperature. In undoped particles the variation of the magnetization and the magnetic viscosity are smaller at low than at room temperature, as expected from the increase of thermal stability of the magnetization with the decrease of temperature. On the contrary, in Co/Ti-doped particles for magnetic recording media, we observe an anomalous increase of the magnetization variation during the time and of magnetic viscosity when the temperature decreases. This behaviour is interpreted on the basis of the evolution of magnetic anisotropy with the temperature in doped Ba ferrite particles, where the magnetocrystalline anisotropy at low temperature becomes comparable with the shape anisotropy.

Thermomagnetics of a system of interacting particles with log normal distribution of particle size and anisotropy constant was studied self-consistently using a Monte Carlo calculation within the mean-field approximation. Characteristic hysteretic behavior and reversible transverse susceptibility (RTS) were investigated. The salient features are as follows: The hysteresis loops become sheared with increasing anisotropy distribution, [[Sigma].sub.K], while their slopes steepen with the mean field strength [Alpha]. For a homogeneous systems RTS peaks increase sharply with [Alpha], both at the anisotropy field [H.sub.K] and coercive field [H.sub.c]. For random systems, both peaks become shallower and blunted with increasing [[Sigma].sub.K]. Mean field strength [Alpha] causes the peak positions of RTS at [H.sub.K] to shift to lower values, while the shift at [H.sub.c] depends subtly upon the interplay among [Alpha], [[Sigma].sub.K] and texture of the system. For random systems the shift is toward higher [H.sub.c] values with increasing [Alpha]. For systems with constant [Alpha], however, it shifts toward lower values with increasing [[Sigma].sub.K].