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Articles you may be interested inEffect of sintering temperature on the magnetic properties of zinc substituted lithium ferrites synthesized using sol-gel method AIP Conf.The magnetization of Li-Zn ferrite, Lio.s_x/2ZnxFe2.s_x/20., with x = 0 to x = 1.0 Zn at./f.u. has been examined over the temperature range 4-950 K and for fields up to 90 kOe. Magnetization M and high-field incremental susceptibility X in, were compared with a calculation based on a localized canting model. A qualitative fit was found for M versus x for an exchange ratio J A.,IJ SS = 3-4, but the experimental and theoretical X in, versus x results were completely different. On the other hand, a good correlation was found between X in, and the probability of a B-site Fe having only one A-site Fe neighbor. The data also revea110wtemperature maxima in M in the 30-80 K range for x = 0.4 up to 1.0; the effect is most pronounced for x = 0.7. Weak mictomagnetic behavior is found for x = 0.5 and 0.6. Samples with x = 0.9 and 1.0 show no spontaneous moment down to 4 K, but exhibit initial susceptibility maxima at about 15 K with extrapolated Curie temperatures of 10 K and 4 K, respectively. For x = 0.8, a Curie temperature of 238 K is obtained. These are considerably lower than literature values.

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A technique for separating anisotropy and porosity induced FMR line-broadening contributions in narrow linewidth polycrystals has been extended to large linewidth lithium ferrite materials. The FMR linewidth is measured versus frequency and temperature T. Since the porosity contribution is proportional to the magnetization 4πMs, and the anisotropy field Ha falls off much faster at high T than does 4πMs, the two contributions to the linebroadening can be separated. Three samples were studied: Li-ferrite with and without cobalt addition (0.01 Co atoms/formula unit), and a Li-ferrite with 0.01 Co and 0.26 Ti at./f.u. The anisotropy field for unsubstituted Li-ferrite was found to decrease monotonically with T with Ha≊ 350 Oe at 25 °C, in agreement with single crystal data. Cobalt addition was found to decrease the room temperature Ha in the Li-ferrite without titanium but not in the Li-Ti-ferrite. This agrees with previous observations of Ti decreasing the effectiveness of Co in reducing the anisotropy.

Ferromagnetic resonance (FMR) in thin films of permalloy and yttrium iron garnet (YIG) has been studied by Brillouin light scattering (BLS) techniques. The measurements were made at 9.4 GHz on 22.4 to 75-nm-thick permalloy films and on 2.1- to 12.8-μm-thick YIG films. Intensity profiles for magnon scattered light versus in-plane applied field were obtained by analyzing the forward scattered light through the films with a high-contrast Fabry–Perot interferometer. The BLS profiles show a signal-to-noise ratio of 10-100 for the permalloy and 100-1000 for the YIG films, depending on the film thickness and the microwave power level. The FMR BLS response was quantified in terms of global response function, counts/s mW versus magnon occupation number Nu. The Nu parameter relates the scattering to the uniform mode FMR response (linewidth, field, frequency, etc.), input microwave power, and active sample volume. The response for permalloy was approximately10−8 counts/s mW magnon, which translates into a limiting sample volume of 10−12 cm3.