The influence of Fe concentration on Y3Al5?xFexO12 garnets
The polycrystalline Y3Al5?xFexO12 compounds with 0?x?5 were produced by solid state reaction technique. The cubic cell parameter and the crystallite size were determined from the powder X-ray analyses, and the transmission electron microscopy (TEM) was used to study the shape, size and crystallinity of the samples. The spectral properties and lattice vibrations were studied by absorption and Raman spectra. Magnetic measurements were achieved by using a superconducting quantum interference device (SQUID). The X-ray diffraction pattern reveals that all the samples appear as a single phase; however, the crystallite sizes determined from X-ray line broadening are increased with increasing the Fe concentration. From the TEM study, irregular nano particles are aggregated in all samples. In general, the crystallite size is increased with the Fe concentration. The Curie temperatures were observed to decrease from 555 to 110 K for samples with x decreasing from 5 to 2.5. For samples with x<1.2, the magnetization decreases very fast. The absorption peak shifts to a large wave number with the Fe concentration. The Raman spectra showed that the changes of lattice vibration would influence interaction between the Fe ion and the host. From the analyses of the measured MT curves and MH diagrams, we found that the samples with doping Fe concentrations less than 50 at.% appeared to be paramagnetic. But, the samples of YIG and 50 at.%Fe:YAG appeared to be ferromagnetic. However, 50 at.%Fe:YAG changes into paramagnetic above 110 K. This implies that there may be a phase change point. On summary, nano-size particles were observed easy to form for samples with increasing the Fe concentration.
y3al5?xfexo12 garnets polycrystalline raman spectrum magnetic property