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The low rare-earth content α-Fe/Nd[SUB2]Fe[SUB14]B nanocomposite magnets having a high soft phase ratio) were fabricated by the rapid quenching method and evaluations were made of the crystallization behavior, microstructure, and magnetic properties in the annealing process. An investigation of the relationship between the roller surface velocity, V[SUBs], and magnetic properties showed that changes)in the crystal grain size of the α-Fe phase following annealing could be attributed to differences in the amorphous content of the as-melt-spun ribbons. As the amorphous content was increased, their crystal grain size tended to become finer and their magnetic properties tended to improve. However, it was observed that the optimum rapid quenching rate exists. The slight presence of clusters in as-melt-spun ribbons is favorable for obtaining good magnetic properties because the growth of a-Fe crystals is inhibited. The presumed reason for this inhibiting effect is that α-Fe growth occurs in a process in which clusters containing Nd expel this element. In the case of a completely amorphous state, large crystals grew easily, because they consisted of only Fe and Co in the initial stage. [ABSTRACT FROM AUTHOR]

Abstract: It is the first report on the recording performance of a perpendicular metal evaporated (ME) tape measured with a giant magnetoresistive head. To solve the application difficulty of oblique evaporated tape media to linear scan tape systems, a perpendicular evaporated Co–CoO tape was proposed instead. The prepared sample showed perpendicular anisotropy with coercivity of 107.3kA/m, M r t of 3.9mA and squareness of 0.25. Identical recording characteristics were obtained for both head-media moving directions, which enables the application of perpendicular evaporated Co–CoO tape to linear scan tape systems. The better carrier-to-noise ratio was also confirmed by comparison with a current advanced product of metal particulate tape, which can realize the higher recording density of linear scan tape systems using ME tape. [Copyright &y& Elsevier]

In order to examine the possibility of applying the HDDR process to segregated master ingots, Nd–Fe–B system HDDR powders were made from ingots with different levels of homogeneity, and their structures and magnetic properties were evaluated in detail. HDDR powders made from segregated as-cast ingots displayed anisotropy and large coercivity. They had a nearly homogeneous Nd2Fe14B phase, although some large areas with α-Fe and Nd-rich regions of 30 μm in size were present after the HD process. With increasing in the homogeneity level of the master ingots, the anisotropy of HDDR-processed powders decreased and their coercivity increased. In addition, an intermediate Ar treatment was applied between the HD and DR processes to improve the magnetic properties. As a result, the effect of the IA treatment was clearly confirmed, and good magnetic properties of Br=1.23 T, HcJ=848 kA/m and (BH)max=238 kJ/m3 were obtained. [Copyright &y& Elsevier]

The hydrogenation disproportionation desorption recombination (HDDR) process was performed on the generally used alloy composition of Nd12.6Fe63.1Co17.4Zr0.1Ga0.3B6.5 and a low rare earth content alloy composition of Nd11.0Fe65.0Co17.8Zr0.1Ga0.3B5.8. A detailed evaluation was made of the relationship between the microstructure and magnetic properties of these HDDR-processed magnetic powders with respect to their different rare earth element concentrations. The HDDR-processed powders of both alloy compositions were transformed to the Nd2Fe14B phase consisting of fine recombined crystal grains of around 400–500 nm in size and maintained the anisotropic magnetic characteristic that was present before HDDR processing. However, reduction of the rare earth content drastically reduced coercivity, and the alloy composition of Nd11.0Fe65.0Co17.8Zr0.1Ga0.3B5.8 did not manifest magnetic properties. From the results of an examination of their microstructures, it was inferred that the coercivity decreased due to a decline in the concentration of the rare earth element at the grain boundaries of the fine Nd2Fe14B grains with the reduction of the rare earth content of the alloys. Accordingly, in magnetic powders obtained by the HDDR process, the nucleation type of coercivity mechanism predominates, in which rare earth-rich regions present at the grain boundaries of fine Nd2Fe14B grains play a large role in the manifestation of coercivity. [Copyright &y& Elsevier]