The effect of Si on the austenite stabilization, martensite morphology, and magnetic properties in Fe-26%Ni-x%Si （x=3.5, 5, and 6） alloys have been studied by means of transmission electron microscopy （TEM） and M...The effect of Si on the austenite stabilization, martensite morphology, and magnetic properties in Fe-26%Ni-x%Si （x=3.5, 5, and 6） alloys have been studied by means of transmission electron microscopy （TEM） and M？ssbauer spectroscopy techniques. TEM observations reveal that the martensite morphology is closely dependent on the Si content. The volume fraction changes of martensite and austenite phases, the hyperfine magnetic field, and isomer shift values have been determined by Mssbauer spectroscopy. The M？ssbauer study reveals that the hyperfine magnetic field, the isomer shift values and the volume fraction of martensite decrease with increasing Si content.展开更多
MgxNi1-xFe_(2)O_(4)(x=0,0.25,0.5,0.75,1)spinel ferrite material was analyzed to determine its magnetic properties and structure.X-ray diffraction(XRD),Mössbauer spectroscopy,and vibrating sample magnetometer(VSM)...MgxNi1-xFe_(2)O_(4)(x=0,0.25,0.5,0.75,1)spinel ferrite material was analyzed to determine its magnetic properties and structure.X-ray diffraction(XRD),Mössbauer spectroscopy,and vibrating sample magnetometer(VSM)characterization were performed on the samples prepared using the sol-gel method.The results from XRD confirmed the existence of the single-phase cubic spinel structures Fd3m,as well as the evolution of the crystalline size(D),the lattice parameter(a)and cell volume in compounds.The Mössbauer spectra showed the distribution of cations and changes in the magnetic properties of the sample.VSM measurement revealed that the samples were room-temperature ferromagnetic.Moreover,the saturation magnetization(Ms)of the samples changed with the Mg^(2+)ion content x,and a maximum occured at x=0.5.Doping with Mg^(2+)ions increased the transfer of Ni^(2+)ions to tetrahedral sites,thus increasing the magnetic moment difference between tetrahedral(A)and octahedral(B)sites.Specifically,doping NiFe_(2)O_(4) with Mg^(2+)ions can enhance its magnetic properties and enhance its saturation magnetization.展开更多
A series of nanostructured iron compounds including cubic Fe3O4 and orthorhombic FeOOH were synthesized via a facile low temperature (in the range of 60-100℃) solution method. In the whole process, the interaction be...A series of nanostructured iron compounds including cubic Fe3O4 and orthorhombic FeOOH were synthesized via a facile low temperature (in the range of 60-100℃) solution method. In the whole process, the interaction between FeCl2·4H2O and methenamine (C6H12N4) was carried out through a reflux device under different reaction conditions such as temperature, solvent, and duration. The samples were detected by XRD, TEM, SAED, physical property measurement system, and Mssbauer spectroscopy, separately. The experiments showed that magnetic mixture nanoparticles had flake and rod morphologies, and cubic Fe3O4 took on grain nanostructure. Magnetism measurements indicated that the saturated magnetization of the as-obtained magnetic mixture was lower than that of the cubic magnetite. Mssbauer spectroscopy testified the sample consisting of cubic magnetite rather than γ-Fe2O3. In addition, a possible growth mechanism of cubic magnetic nanoparticles under different conditions was discussed.展开更多
Mixed-oxide nanostructures of the type xGd<sub>2</sub>O<sub>3</sub>-(1-x)α-Fe<sub>2</sub>O<sub>3</sub> (x=0.1, 0.3, 0.5 and 0.7) were synthesized by mechanochemical act...Mixed-oxide nanostructures of the type xGd<sub>2</sub>O<sub>3</sub>-(1-x)α-Fe<sub>2</sub>O<sub>3</sub> (x=0.1, 0.3, 0.5 and 0.7) were synthesized by mechanochemical activation for ball milling times of 0, 2, 4, 8 and 12 hours. The systems were subsequently analyzed by Mӧssbauer spectroscopy, X-ray powder diffraction (XRPD), magnetic measurements and optical diffuse reflectance spectroscopy. The magnetic hyperfine field was studied as function of ball milling time for all sextets involved and found to be consistent with the formation of a limited solid solution in the systems investigated. The end-product was the gadolinium perovskite, represented by a doublet whose abundance was derived as function of the milling time. The XRPD patterns recorded for the equimolar composition were dominated by the diffraction peaks of GdFeO<sub>3</sub> after 12 hours of milling. The hysteresis loops were recorded at 300 and 5 K in an applied magnetic field of 5 T and were interpreted as a superposition of paramagnetic behavior of gadolinium oxide and weak ferromagnetic behavior of hematite and gadolinium perovskite. The Morin transition of hematite was inferred from zero-field-cooling-field-cooling (ZFC-FC) curves measured with a magnetic field of 200 Oe in the 5-300 K temperature range and was found to depend on the ball milling time. Optical diffuse reflectance spectra showed that the compounds were semiconductors with an optical band gap of 2.1 eV.展开更多
Ti doped hematitea-Fe_(2-x)Ti_(x)O_(3)(x=0.0,0.0206 and 0.0344)samples are synthesized using solid-state ceramic route technique.Single phase and corundum(Al_(2)O_(3))type structure is revealed from the X-ray diffract...Ti doped hematitea-Fe_(2-x)Ti_(x)O_(3)(x=0.0,0.0206 and 0.0344)samples are synthesized using solid-state ceramic route technique.Single phase and corundum(Al_(2)O_(3))type structure is revealed from the X-ray diffraction(XRD)pattern.On substitution of Ti at Fe site,all Raman active modes are shifted to higher wave numbers.An additional feature of Eu(LO)mode at about 660 cm^(-1)is observed.The E_(u) mode frequency is decreased and pronounced systematically as a function of Ti doping,and it reaches a value of 658 cm^(-1)for x=0.0344.The coercivity Hc(remanence M_(r))for x=0.0,0.0206 and 0.0344 are determined to be 995 Oe(0.44 emu/mg),1404 Oe(0.00019 emu/mg)and 2023 Oe(0.00016 emu/mg),respectively.The larger coercivity for Ti doped samples can be attributed to their enhanced shape and magneto-crystalline anisotropy.The observed isomer shift(d)from room temperature Mössbauer data clearly shows the presence of ferric(Fe^(3+))and Ti^(4+)ordering ofa-Fe_(2-x)Ti_(x)O_(3)for x=0.0344.展开更多
Rare-earth ferrite garnet is one of the most important materials applied in microwave transducer and in- frared magneto-optical devices, etc. Nd3-xAExFe5O12（AE=Ca, Sr） crystals, which have cubic structure with the s...Rare-earth ferrite garnet is one of the most important materials applied in microwave transducer and in- frared magneto-optical devices, etc. Nd3-xAExFe5O12（AE=Ca, Sr） crystals, which have cubic structure with the space group ofIa-3 d and lattice constants over 1.26 nm, were prepared via the mild hydrothermal method. The structural, morhpology and magnetic properties were characterized by means of powder X-ray diffraction, scanning electronic microscopy, as well as vibrating sample magnetometer and M6ssbauer spectroscopy, respectively. M6ssbaner spectroscopy demonstrates the coexistence of Sr2＋, Ca2＋ and Nd3＋ at the C sites of the dodecahedrons for different substituted garnets. The crystal shape is dodecahedron, and the particle sizes are decreased with increasing the Ca and Sr doping concentrations. By recording the magnetic hysteresis loops and M-T curves at different temperatures, it can be seen that with the increasing x, the saturation magnetization values decrease while the coercive forces increase under the condition of high temperatures.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
Solid-state ceramic technique route is used for synthesizing Cr-doped haematiteaα-Fe_(2-x)Cr_(x)O_(3)(x=0,0.125,0.50 and 1)samples.Single phase and corundum(Al2O_(3))type structure is revealed from the X-ray diffract...Solid-state ceramic technique route is used for synthesizing Cr-doped haematiteaα-Fe_(2-x)Cr_(x)O_(3)(x=0,0.125,0.50 and 1)samples.Single phase and corundum(Al2O_(3))type structure is revealed from the X-ray diffraction(XRD)patterns.The Raman spectra ofαa-Fe_(2-x)Cr_(x)O_(3)illustrate seven phonon modes.On substitution of Cr(x=0,0.125,0.50 and 1)at Fe site,all Raman active modes are shifted to higher wave numbers.The coercivity and remanence of Cr-doped haematites increase as x increases.The increased coercivity and remanence for Cr-doped samples can be attributed to their enhanced shape and magneto-crystalline anisotropy.The observed isomer shiftδdvalues from room-temperature Mössbauer data clearly show the presence of ferric(Fe^(3+))and Cr^(3+)ions illustrating strong ferromagnetic ordering up to x=0.125 inaα-Fe_(2-x)Cr_(x)O_(3)haematite and weak ferromagnetic ordering foraα-Fe2-xCrxO_(3)(x>0.125)haematites.展开更多
基金supported by the Research Fund of Kirikkale University (No.2006/15)
文摘The effect of Si on the austenite stabilization, martensite morphology, and magnetic properties in Fe-26%Ni-x%Si （x=3.5, 5, and 6） alloys have been studied by means of transmission electron microscopy （TEM） and M？ssbauer spectroscopy techniques. TEM observations reveal that the martensite morphology is closely dependent on the Si content. The volume fraction changes of martensite and austenite phases, the hyperfine magnetic field, and isomer shift values have been determined by Mssbauer spectroscopy. The M？ssbauer study reveals that the hyperfine magnetic field, the isomer shift values and the volume fraction of martensite decrease with increasing Si content.
基金Project supported by the National Natural Science Foundation of China (Grant No.11447231)the National Undergraduate Innovation and Entrepreneurship Training Program Support Projects of China+2 种基金the Natural Science Foundation of Hunan Province,China (Grant No.2020JJ4517)the Research Foundation of the Education Bureau of Hunan Province,China (Grant Nos.19A434,19A433,and 19C1621)the Opening Project of the Cooperative Innovation Center for Nuclear Fuel Cycle Technology and Equipment,University of South China (Grant Nos.2019KFY10 and 2019KFY09)。
文摘MgxNi1-xFe_(2)O_(4)(x=0,0.25,0.5,0.75,1)spinel ferrite material was analyzed to determine its magnetic properties and structure.X-ray diffraction(XRD),Mössbauer spectroscopy,and vibrating sample magnetometer(VSM)characterization were performed on the samples prepared using the sol-gel method.The results from XRD confirmed the existence of the single-phase cubic spinel structures Fd3m,as well as the evolution of the crystalline size(D),the lattice parameter(a)and cell volume in compounds.The Mössbauer spectra showed the distribution of cations and changes in the magnetic properties of the sample.VSM measurement revealed that the samples were room-temperature ferromagnetic.Moreover,the saturation magnetization(Ms)of the samples changed with the Mg^(2+)ion content x,and a maximum occured at x=0.5.Doping with Mg^(2+)ions increased the transfer of Ni^(2+)ions to tetrahedral sites,thus increasing the magnetic moment difference between tetrahedral(A)and octahedral(B)sites.Specifically,doping NiFe_(2)O_(4) with Mg^(2+)ions can enhance its magnetic properties and enhance its saturation magnetization.
基金Supported by the "Plan of Outstanding Talents" of Chinese Academy of Sciences and the National Natural Science Foundation of China (Grant No. 50673078)
文摘A series of nanostructured iron compounds including cubic Fe3O4 and orthorhombic FeOOH were synthesized via a facile low temperature (in the range of 60-100℃) solution method. In the whole process, the interaction between FeCl2·4H2O and methenamine (C6H12N4) was carried out through a reflux device under different reaction conditions such as temperature, solvent, and duration. The samples were detected by XRD, TEM, SAED, physical property measurement system, and Mssbauer spectroscopy, separately. The experiments showed that magnetic mixture nanoparticles had flake and rod morphologies, and cubic Fe3O4 took on grain nanostructure. Magnetism measurements indicated that the saturated magnetization of the as-obtained magnetic mixture was lower than that of the cubic magnetite. Mssbauer spectroscopy testified the sample consisting of cubic magnetite rather than γ-Fe2O3. In addition, a possible growth mechanism of cubic magnetic nanoparticles under different conditions was discussed.
文摘Mixed-oxide nanostructures of the type xGd<sub>2</sub>O<sub>3</sub>-(1-x)α-Fe<sub>2</sub>O<sub>3</sub> (x=0.1, 0.3, 0.5 and 0.7) were synthesized by mechanochemical activation for ball milling times of 0, 2, 4, 8 and 12 hours. The systems were subsequently analyzed by Mӧssbauer spectroscopy, X-ray powder diffraction (XRPD), magnetic measurements and optical diffuse reflectance spectroscopy. The magnetic hyperfine field was studied as function of ball milling time for all sextets involved and found to be consistent with the formation of a limited solid solution in the systems investigated. The end-product was the gadolinium perovskite, represented by a doublet whose abundance was derived as function of the milling time. The XRPD patterns recorded for the equimolar composition were dominated by the diffraction peaks of GdFeO<sub>3</sub> after 12 hours of milling. The hysteresis loops were recorded at 300 and 5 K in an applied magnetic field of 5 T and were interpreted as a superposition of paramagnetic behavior of gadolinium oxide and weak ferromagnetic behavior of hematite and gadolinium perovskite. The Morin transition of hematite was inferred from zero-field-cooling-field-cooling (ZFC-FC) curves measured with a magnetic field of 200 Oe in the 5-300 K temperature range and was found to depend on the ball milling time. Optical diffuse reflectance spectra showed that the compounds were semiconductors with an optical band gap of 2.1 eV.
文摘Ti doped hematitea-Fe_(2-x)Ti_(x)O_(3)(x=0.0,0.0206 and 0.0344)samples are synthesized using solid-state ceramic route technique.Single phase and corundum(Al_(2)O_(3))type structure is revealed from the X-ray diffraction(XRD)pattern.On substitution of Ti at Fe site,all Raman active modes are shifted to higher wave numbers.An additional feature of Eu(LO)mode at about 660 cm^(-1)is observed.The E_(u) mode frequency is decreased and pronounced systematically as a function of Ti doping,and it reaches a value of 658 cm^(-1)for x=0.0344.The coercivity Hc(remanence M_(r))for x=0.0,0.0206 and 0.0344 are determined to be 995 Oe(0.44 emu/mg),1404 Oe(0.00019 emu/mg)and 2023 Oe(0.00016 emu/mg),respectively.The larger coercivity for Ti doped samples can be attributed to their enhanced shape and magneto-crystalline anisotropy.The observed isomer shift(d)from room temperature Mössbauer data clearly shows the presence of ferric(Fe^(3+))and Ti^(4+)ordering ofa-Fe_(2-x)Ti_(x)O_(3)for x=0.0344.
文摘Rare-earth ferrite garnet is one of the most important materials applied in microwave transducer and in- frared magneto-optical devices, etc. Nd3-xAExFe5O12（AE=Ca, Sr） crystals, which have cubic structure with the space group ofIa-3 d and lattice constants over 1.26 nm, were prepared via the mild hydrothermal method. The structural, morhpology and magnetic properties were characterized by means of powder X-ray diffraction, scanning electronic microscopy, as well as vibrating sample magnetometer and M6ssbauer spectroscopy, respectively. M6ssbaner spectroscopy demonstrates the coexistence of Sr2＋, Ca2＋ and Nd3＋ at the C sites of the dodecahedrons for different substituted garnets. The crystal shape is dodecahedron, and the particle sizes are decreased with increasing the Ca and Sr doping concentrations. By recording the magnetic hysteresis loops and M-T curves at different temperatures, it can be seen that with the increasing x, the saturation magnetization values decrease while the coercive forces increase under the condition of high temperatures.
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.
基金Authors are thankful to UGC New Delhi for financial assistance
文摘Solid-state ceramic technique route is used for synthesizing Cr-doped haematiteaα-Fe_(2-x)Cr_(x)O_(3)(x=0,0.125,0.50 and 1)samples.Single phase and corundum(Al2O_(3))type structure is revealed from the X-ray diffraction(XRD)patterns.The Raman spectra ofαa-Fe_(2-x)Cr_(x)O_(3)illustrate seven phonon modes.On substitution of Cr(x=0,0.125,0.50 and 1)at Fe site,all Raman active modes are shifted to higher wave numbers.The coercivity and remanence of Cr-doped haematites increase as x increases.The increased coercivity and remanence for Cr-doped samples can be attributed to their enhanced shape and magneto-crystalline anisotropy.The observed isomer shiftδdvalues from room-temperature Mössbauer data clearly show the presence of ferric(Fe^(3+))and Cr^(3+)ions illustrating strong ferromagnetic ordering up to x=0.125 inaα-Fe_(2-x)Cr_(x)O_(3)haematite and weak ferromagnetic ordering foraα-Fe2-xCrxO_(3)(x>0.125)haematites.
