The rare earth iron garnets R3Fe5O12（R=Sm, Eu） were synthesized under mild hydrothermal conditions, and their crystal growth was found to be sensitive to alkalinity, reaction temperature and time. The as-prepared sa...The rare earth iron garnets R3Fe5O12（R=Sm, Eu） were synthesized under mild hydrothermal conditions, and their crystal growth was found to be sensitive to alkalinity, reaction temperature and time. The as-prepared samples were characterized by powder X-ray diffraction（XRD）, scanning electron microscopy（SEM）, infrared spectra（IR） and Raman spectrum. The M vs. H loops and magnetic parameters have been traced with a vibrating sample magnetometer（VSM） and superconducting quantum interference devices（SQUIDs） magnetometer. We proposed the formation mechanisms and formulated a reasonable explanation for their growth habits. Different morphologic characteristics were observed by changing alkalinity in the reaction systems. The magnetic studies gave saturation magnetization（Ms） and Curie temperature（TC）. The magnetic behaviors of Sm3Fe5O12 and Eu3Fe5O12 in mild hydrothermal systems are comparable with those in high temperature solid state reactions.展开更多
Ga-doped Yttrium Iron Garnet (Y_(3)Ga_(x)Fe_(5-x)O_(12),Ga:YIG) was prepared by solid state reaction method and sintering at 1 300 ℃.Rietveld analysis of X-ray diffraction patterns indicated that all samples crystall...Ga-doped Yttrium Iron Garnet (Y_(3)Ga_(x)Fe_(5-x)O_(12),Ga:YIG) was prepared by solid state reaction method and sintering at 1 300 ℃.Rietveld analysis of X-ray diffraction patterns indicated that all samples crystallized in a single cubic structure (space group Ia-3d) with decreasing lattice constant as Ga concentration increased.SEM surface micrograph images of YIG samples showed highly compacted grains with small reduction in the grain size with increasing Ga concentration.Raman spectroscopy measurements confirmed the replacement of Fe^(3+) ions by Ga^(3+) ions in the garnet structure was revealed by the observed blue shifts in Raman spectra.The saturation magnetization decreased from 28.2 to 4.98 emu g^(-1) with increasing x from 0.0 to 1.0 due to the preferential substitution of Ga^(3+) ions for Fe^(3+) ions at tetrahedral sites.Room temperature Mössbauer spectra for the samples revealed a reduction of the hyperfine field values for octahedral and tetrahedral sites,and the development of additional components with increasing Ga concentration.Analysis of the magnetic data and Mössbauer spectra confirmed that spin canting in the substituted garnets plays an important role in explaining the observed reduction of the saturation magnetization as x increased.展开更多
基金Supported by the National Natural Science Foundation of China(Nos.90922034, 20771042)
文摘The rare earth iron garnets R3Fe5O12（R=Sm, Eu） were synthesized under mild hydrothermal conditions, and their crystal growth was found to be sensitive to alkalinity, reaction temperature and time. The as-prepared samples were characterized by powder X-ray diffraction（XRD）, scanning electron microscopy（SEM）, infrared spectra（IR） and Raman spectrum. The M vs. H loops and magnetic parameters have been traced with a vibrating sample magnetometer（VSM） and superconducting quantum interference devices（SQUIDs） magnetometer. We proposed the formation mechanisms and formulated a reasonable explanation for their growth habits. Different morphologic characteristics were observed by changing alkalinity in the reaction systems. The magnetic studies gave saturation magnetization（Ms） and Curie temperature（TC）. The magnetic behaviors of Sm3Fe5O12 and Eu3Fe5O12 in mild hydrothermal systems are comparable with those in high temperature solid state reactions.
文摘Ga-doped Yttrium Iron Garnet (Y_(3)Ga_(x)Fe_(5-x)O_(12),Ga:YIG) was prepared by solid state reaction method and sintering at 1 300 ℃.Rietveld analysis of X-ray diffraction patterns indicated that all samples crystallized in a single cubic structure (space group Ia-3d) with decreasing lattice constant as Ga concentration increased.SEM surface micrograph images of YIG samples showed highly compacted grains with small reduction in the grain size with increasing Ga concentration.Raman spectroscopy measurements confirmed the replacement of Fe^(3+) ions by Ga^(3+) ions in the garnet structure was revealed by the observed blue shifts in Raman spectra.The saturation magnetization decreased from 28.2 to 4.98 emu g^(-1) with increasing x from 0.0 to 1.0 due to the preferential substitution of Ga^(3+) ions for Fe^(3+) ions at tetrahedral sites.Room temperature Mössbauer spectra for the samples revealed a reduction of the hyperfine field values for octahedral and tetrahedral sites,and the development of additional components with increasing Ga concentration.Analysis of the magnetic data and Mössbauer spectra confirmed that spin canting in the substituted garnets plays an important role in explaining the observed reduction of the saturation magnetization as x increased.
