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We report the fabrication of planar microstripline reciprocal phase shifter using a bulk Yttrium Iron Garnet (YIG) material. The propagation direction of the microstripline and magnetization direction of the YIG is collinear, and the length of the microstripline and the YIG was 50 mm in length. The proposed design shows large differential phase shifts of 100 degrees for applied magnetic fields varying from 0 to 0.56 times 104 A/m over the frequency range of 1.2 GHz between 5.4 GHz and 6.6 GHz. The average insertion loss, ~ 2.5 dB, was measured to have a 20% bandwidth at 6 GHz. The planar phase shifter presented here demonstrates a compact design, low loss, and an especially large phase shift with a relatively small bias field.

Disordered nanocrystalline Ni3Fe alloy was prepared by mechanical alloying of elemental powders. X-ray diffractograms show the formation of Ni3Fe single phase. The chemical composition and morphology of the powder have been obtained by using EDAX and SEM analysis respectively. While the saturation magnetisation decreases with milling time, the coercivity increases. The width of the hyperfine field distributions obtained from Mossbauer studies shows that the alloy is highly disordered Atomic ordering is found to take place at a faster rate compared to that in the bulk alloy. (C) 1999 Acta Metallurgica Inc.

We report here the magnetocaloric effect (MCE) in bulk and nanostructured gadolinium iron garnets (Gd3Fe5O12). When compared with the bulk counterpart, the magnitude of the MCE is smaller for nanostructured samples with an average grain size of 50nm, but increases when the grain size decreases to 35nm. For the bulk sample, the MCE curves show a broad peak at 35K; this peak is found to shift to lower temperatures for the nanostructured samples. The origin of the MCE peak for the bulk sample is associated with the intrinsic magnetic frustration and the ferromagnetic ordering of the Gd sublattice below 90K, while for nanostructured garnets it is additionally ascribed to the surface spin disorder and particle blocking effects. While blocking is detrimental to achieving large MCE, surface spin disorder is found to enhance it under high applied fields. (Some figures in this article are in colour only in the electronic version)