Results of studying the specific features of formation of the crystal structure and distribution of iron cations over the sites in the DyFeTi2O7 compound have been presented and the comparison with the GdGaTi2O7 isostructural compound has been performed. The atomic disorder in the distribution of the Fe3+ ions over structural sites in the DyFeTi2O7 compound is confirmed by the Mössbauer spectroscopy and X-ray diffractometry. The results of magnetic measurements in the low-temperature region have revealed an inflection point in the temperature dependence of the magnetic moment and its dependence on the magnetic prehistory of the sample. The obtained experimental data suggest that there is a spin glass state with freezing point Tf = 6 K in the DyFeTi2O7 compound. 相似文献
The magnetic properties of a synthesized dielectric NaFeGe2O6. polycrystal have been studied. The antiferromagnetic ordering of this compound below 15 K has been established. The Mössbauer spectrum at 300 K is a quadrupole doublet; it is characterized by an isomeric shift typical of the high-spin Fe3+ ion in the octahedral coordination and quadrupole splitting, which indicates distortion of the oxygen octahedron around the iron cation. Quasi-one-dimensionality of the sample magnetic structure is proved. 相似文献
The X-ray diffraction, M?ssbauer, calorimetric, and magnetic characteristics of zirconolite GdFeTi2O7 have been measured to determine the ground magnetic state. A kink dependent on the magnetic prehistory of the sample has been revealed in the temperature dependence of the magnetic moment at T = 3 K. M?ssbauer spectroscopy has confirmed the nonequivalence of the iron ion positions in GdFeTi2O7. The experimental data obtained allow the conclusion on the formation of a spin glass state with the freezing temperature Tf = 3 K in the GdFeTi2O7 compound. 相似文献
The results of the experimental investigation of the magnetic properties of the SmFeGe2O7 compound have been presented. It has been found that the temperature dependence of the susceptibility exhibits two features that coincide with the anomalies in the temperature dependence of the specific heat and indicate magnetic phase transitions in SmFeGe2O7. The external magnetic field induces a magnetic transition, the critical field of which depends on the temperature. 相似文献
Complex studies have been performed for the structural, static magnetic, and resonance properties of a new magnet LiCuFe2(VO4)3 prepared by solid-phase synthesis. The temperature dependence of the susceptibility has an anomaly at temperature Tmax = 9.6 K. At high temperatures, the LiCuFe2(VO4)3 sample is in the paramagnetic state described by the Curie–Weiss law at T > 50 K and mainly determined by iron ions with effective magnetic moment μeff(exp) = 8.6μB per formula unit. At low temperatures, a long-range magnetic order is observed in the magnetic subsystem of the sample; the order is predominantly characterized by the antiferromagnetic exchange interaction and high frustration level. The exchange interaction parameters are estimated in a six-sublattice representation of the LiCuFe2(VO4)3 magnet. It is shown that the LiCuFe2(VO4)3 compound is an antiferromagnet with strong intrachain and frustrating interchain exchange interactions. 相似文献
Physics of the Solid State - The structural, thermal, static magnetic, and resonance properties of the low-dimensional NaCuFe2(VO4)3 compound obtained by the solid-phase synthesis have been... 相似文献
The magnetic structure of the NaFeGe2O6 monoclinic compound has been experimentally investigated using the elastic scattering of neutrons. At a temperature of 1.6
K, an incommensurate magnetic structure has been observed in the form of an antiferromagnetic helix formed by a pairs of the
spins of the Fe3+ ions with helical modulation in the ac plane of the crystal lattice. The wave vector of the magnetic structure has been determined and its temperature behavior
has been studied. The analysis of the temperature dependences of the specific heat and susceptibility, as well as the isotherms
of the field dependence of the magnetization, has revealed the existence of not only the order-disorder magnetic phase transition
at the point TN = 13 K, but also an additional magnetic phase transition at the point Tc = 11.5 K, which is assumingly an orientation phase transition. 相似文献
The polycrystalline compound LiFeGe2O6 has been synthesized by the solid-phase reaction. The X-ray diffraction, Mössbauer, calorimetric, and magnetic investigations have been carried out. The Mössbauer spectrum at 300 K represents a single quadrupole doublet. The isomer shift with respect to the metal iron α-Fe is 0.40 mm/s, which is characteristic of the Fe3+ high-spin ion in the octahedral coordination. The quadrupole splitting of 0.42 mm/s indicates a distortion of the oxygen octahedron around the iron cation. The results of the measurement of the temperature dependence of the heat capacity in the range 2–300 K have shown the presence of the only anomaly with a maximum at Tm ~ 20.5 K, which indicates the occurrence of a magnetic phase transition in this point. The data of the measurement of the temperature dependence of the magnetization have confirmed that the magnetic order with the dominant antiferromagnetic interaction of magnetically active ions exists in LiFeGe2O6 at a temperature below 20.5 K. The investigation of the temperature dependence of the heat capacity in the magnetic field H up to 9 T has demonstrated that the external factor insignificantly changes the order-disorder transition point (at H = 9 T, there occurs a shift of ~0.5 K toward the low-temperature range).
We report on the synthesis conductions and results of experimental investigations of the crystal structure and magnetic properties of a new magnetic compound YbFeTi2O7. According to the X-ray diffractometry data, the crystal structure of the investigated compound is described by the rhombic space group Pcnb with unit cell parameters of a = 9.8115(1) Å, b = 13.5106(2) Å, and c = 7.31302(9) Å and atomic disordering in the distribution of iron ions Fe3+ over five structural sites. The magnetic measurements in the lowtemperature region revealed a kink in the temperature dependence of the magnetic moment and its dependence on the sample magnetic prehistory. The experimental results obtained suggest that with a decrease in temperature the sample passes from the paramagnetic state to the spin-glass-like magnetic state characterized by a freezing temperature of Tf = 4.5 K at the preferred antiferromagnetic exchange coupling in the sample spin system. The chemical pressure variation upon replacement of rare-earth ion R by Yb in the RFeTi2O7 system does not change the crystal lattice symmetry and magnetic state. 相似文献
NaFeGe2O6 polycrystals were synthesized and their x-ray diffraction, magnetic, electrical, and Mössbauer characteristics were measured. It is established that this monoclinic compound is a dielectric with a temperature of antiferromagnetic ordering of 15 K. The Mössbauer spectrum at 300 K is a quadrupole doublet. The isomer shift is 0.40 mm/s, which is characteristic of the high-spin Fe3+ ion in the octahedral coordination. The quadrupole splitting is 0.34 mm/s, which indicates that the oxygen octahedron around the iron cation is distorted. The exchange interactions are estimated, and the crystal magnetic structure is discussed. 相似文献