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We have synthesized the Ba2−xSrxCo2Fe12O22 samples (x = 0.1, 0.2, 0.3, 0.4, 0.5) by the solid-state reaction method and investigated their crystalline and magnetic properties by X-ray diffractometer (XRD), Mössbauer spectrometer, vibrating sample magnetometer, and network analyzer. XRD patterns show that all samples are rhombohedral with space group R-3m. The lattice constants a0 and c0 decrease with Sr substitution due to smaller ion radius of Sr2+ (1.27 Å) than that of Ba2+ (1.43 Å). The Mössbauer spectroscopy measurements show that the relative area ratios of Fe ion were maintained constant regardless of the Sr concentration. However, average magnetic hyperfine field slightly increased with the Sr concentration. This observation agrees with the fact that the saturation magnetization (Ms) linearly increases due to the increasing super-exchange interaction, originated from the difference in the ionic radius between Ba2+ and Sr2+. To investigate its properties at high frequency range, all samples were sintered at 1100 °C, and complex permeability and permittivity were measured by network analyzer between 100 MHz and 4 GHz. For x below 0.3, the initial permeability at 100 MHz increases, at higher values of x, its value decreases. Our study shows that magnetic properties of Sr2+ substitution for Ba2+ in Y-type hexaferrite as well as low magnetic loss less than 0.1 in 1 GHz band, indicating the potential application of Ba2−xSrxCo2Fe12O22 samples for RF and antenna devices in ultra high frequency band.

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Die Ergebnisse der magnetischen Messungen im Temp.‐Bereich 4.2‐30O K werden im Hinblick auf die Kristallstruktur der Titelverbindung diskutiert.

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The crystal structure of LiNi0.99 F57e0.01 PO4 compound has been determined to be orthorhombic by Rietveld refinement method. Temperature dependence of magnetization M shows an anomalous antiferromagnetic behavior. A sudden change in both the magnitude of magnetic hyperfine field and its slope below 11 K suggests that magnetic phase transition related to the spin ordering takes place abruptly. From the result of Mössbauer measurement, it is shown that a strong electric crystalline field of octahedral symmetry including the contribution of spin-orbit coupling and magnetic hyperfine field by space-modulated spin structure is acted to the sites of Fe2+ ions simultaneously at low temperature.