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The NiFe2O4 ferrite powders are synthesized at different ferritization temperatures using a sol-gel method. An analysis of their phase composition, structural characteristics and magnetic properties is performed. It is revealed that additional ferritization leads to an increase in the content of the target phase of the synthesized ferrites. The values of specific saturation magnetization, coercive force, anisotropy fields and Curie temperature are determined. [ABSTRACT FROM AUTHOR]

It is known that the anisotropic magnetic fields are improved by La and Co substitutions for M-type ferrite sintered magnets, and the coercive forces are significantly improved. On the other hand, since W-type ferrites have a crystal structure similar to that of M-type ferrites, it is expected that La-Co substitution would improve magnetic properties in the same way. However, evaluations of the effects of La and Co substitution are difficult because sintered bodies with a single phase of W-type has not been obtained and sintering at high temperatures is required. Recently, a method to determine the anisotropic magnetic fields using the saturation asymptotic law was proposed by T. Kuno et al., J. Jpn. Soc. Powder Powder Metallurgy 63 (2016) 1053, which makes it possible to evaluate the anisotropic magnetic fields. In this study, La-Co substituted W-type ferrite powders in the Ba, Sr and (Ba-Sr) based systems were prepared, and the effects of La-Co substitution and the ratio of Ba and Sr on the anisotropic magnetic fields were investigated. [ABSTRACT FROM AUTHOR]

Excellent gyromagnetic properties of textured, bulk Ba-hexaferrite samples are required for low-loss, self-biased applications for microwave and millimeter-wave (MMW) devices. However, conventionally processed bulk Ba-hexaferrite ceramics typically demonstrate low remanent magnetization values, 4πMr, of 2.0~3.0 kG, and relatively large ferromagnetic resonance (FMR) linewidths, ΔHFMR, of 0.8~2 kOe. These properties lead to the development of high-performance, practical devices. Herein, crystallographically textured Ba-hexaferrite samples, of the composition Ba0.8La0.2Fe11.8Cu0.2O19, having excellent functional properties, are proposed. These materials exhibit strong anisotropy fields, Ha, of ~14.6 kOe, high remanent magnetization, 4πMr, of 3.96 kGs, and a low ΔHFMR of 401 Oe at zero-bias field at the Q-band. Concomitantly, the broadband millimeter-wave transmittance was utilized to determine the complex permeability, μ*, and permittivity, ε*, of textured hexaferrites. Based on Schlöemann's theory of complex permeability, μ*, the remanent magnetization, 4πMr, anisotropy field, Ha, and effective linewidth, ΔHeff, were estimated; these values agree well with measured values. [ABSTRACT FROM AUTHOR]

Abstract: The imaginary part of the second harmonic of the reversible parallel susceptibility (RPS) has been recently demonstrated to be a sensitive probe for determining the anisotropy fields in polycrystalline hard magnetic materials, by means of the singular point detection technique (SPD). A modified SPD theory is depicted here considering the presence of domain walls in the multi-domain crystallites, on the basis of Néel''s phase theory. Measurements performed on Ba-ferrite random powder show that the energy losses related to domain wall motion are likely at the origin of the observed effect. [Copyright &y& Elsevier]

The magnetic properties of sputtered iron-based films can be significantly different when deposited on sloping surfaces. For example, anisotropy fields, H/sub k/, and easy axis coercivities, H/sub ce/, of Fe(N)/NiFe(N) films in this study were as much as two orders of magnitude higher on 60/spl deg/ tilted surfaces than on flat surfaces. The use of high substrate bias during deposition effectively lessened increases of H/sub k/ and H/sub ce/. These parameters were largely independent of the nitrogen content of the films, implying the observed increases were not strongly dependent on magnetostriction. The large H/sub k/ and the H/sub ce/ values are believed to be caused by a shape anisotropy associated with angle-of-incidence deposition and film crystallite morphology. [ABSTRACT FROM PUBLISHER]

Thin films of Nd/sub 2/Fe/sub 14/B (/spl sim/30-60 nm) were grown with c-axis texture by means of molecular beam epitaxy. A two-phase structure is observed in both the X-ray diffraction and the hysteresis loops, due to an interfacial reaction during the initial growth. Coercivities are 1-2 T at 20 K, and the anisotropy fields are bulk-like. Microstructural analysis by atomic and magnetic force microscopies reveal lateral grain sizes of /spl sim/200 nm, which could explain the hard magnetic properties. [ABSTRACT FROM PUBLISHER]