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  • 1
    Electronic Resource
    Electronic Resource
    Electronic and magnetic structure of Fe ions in NiCr2S4 : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5739-5741 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic semiconductor NixFe1−xCr2S4 (x=0.985, 0.97, 0.96) has been investigated over the temperature range from 12 to 600 K using a Mössbauer technique. The electronic structure of Fe ions in NiCr2S4 was calculated with the Hamiltonian incorporating free-ion term, axial and rhombic crystal field, spin-orbital couplings, and exchange interactions. The ground orbital state is separated by 9.64 ||λ|| from the first excited state, thereby making the quadrupole splitting somewhat insensitive to temperature. Using x-ray crystallographic data, the contribution of direct lattice sum to the electric-field gradient has been considered. In calculating the temperature dependence of quadrupole splitting, the axial field parameter Δ1=−3.0||λ||, the rhombic field parameter Δ2=−2.8||λ||, and the covalency factor α2=0.73 in Ni0.985Fe0.015Cr2S4 were determined. Magnetic hyperfine and quadrupole interactions in the antiferromagnetic state of Ni0.96Fe0.04Cr2S4 at 12 K have been studied, yielding the following results: H=147.8 kOe, 1/2e2qQ(1+1/3η2)1/2=−1.96 mm/s, θ=66°, φ=90°, and η=1.0. The line broadening which suggests the electron relaxation was observed with decreasing temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353609
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  • 2
    Electronic Resource
    Electronic Resource
    Site preference for Zn2+ and Ge4+ in mixed ferrite ZnxGe1−xFe2O4 : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6298-6300 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Small amounts of Zn2+ and Ge4+ substituting for GeFe2O4 and ZnFe2O4, can efficiently increase the Neél temperature, thereby can be applied to magnetic device. The site preference of Fe2+ and Fe3+ in mixed ferrite ZnxGe1−xFe2O4 (X=0.6) with Mössbauer absorption and x-ray diffraction was studied. Analysis of x-ray diffraction indicates that the lattice constant is not in accord with Vegard's law, suggesting Fe2+ and Fe3+ are located not only at B sites but at A sites. It is found that Debye temperatures of GeFe2O4 and ZnFe2O4 are 380±5 K and 361±5 K from Mössbauer measurements. Zn2+ and Ge4+ randomly occupy A site or B site. Mössbauer spectra of Zn0.6Ge0.4Fe2O4 reveal line broadening with increasing temperature and the relaxation effect at low temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352676
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  • 3
    Electronic Resource
    Electronic Resource
    Magnetic properties of the monoclinic FeRh2Se4 : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5707-5709 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: FeRh2Se4 has been studied by x-rays, Mössbauer spectroscopy, and superconducting quantum interference device (SQUID) magnetometry. Mössbauer spectra of FeRh2Se4 have been taken at various temperatures ranging from 4.2 to 550 K. Magnetic hyperfine and quadrupole interactions at 4.2 K have been fitted, yielding the following results: H=161.6 kOe, 1/2e2qQ(1+1/3η2)1/2=−0.93 mm/s, θ=61°, φ=0°, and η=0.1. The temperature dependence of the quadrupole splitting, calculated in terms of direct lattice-sum calculations using x-ray crystallographic data, is in good agreement with experimental values up to 550 K. The axial field parameter Δ1=2.0||λ||, the rhombic field parameter Δ2=3.3||λ||, and the covalency factor α2=0.65 were obtained. Magnetic susceptibility measurements by dc SQUID magnetometry show that superexchange interactions between Fe2+ ions are antiferromagnetic.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353598
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  • 4
    Electronic Resource
    Electronic Resource
    Crystallographic and magnetic properties of the spinel phase for NixFe1−xCr2S4 : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6986-6988 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ferrimagnetic NixFe1−xCr2S4 is found to crystallize with a pure spinel structure in the composition range 0≤x≤0.4. 57Fe Mössbauer spectra of NixFe1−xCr2S4 have been taken at various temperatures ranging from 13 K to room temperature. Analysis of Mössbauer spectra and x-ray crystallographic data indicate that Ni ions occupy the tetrahedral site, and the lattice constant is in good agreement with Vegard's law. The isomer shifts indicate that the valence states of the Fe ions have a ferrous character. The Néel temperature increases linearly with Ni concentration, suggesting that the superexchange interaction for Ni-S-Cr link is stronger than that for Fe-S-Cr link. The anomalous reduction of the magnetic hyperfine field below 70 K could be explained in terms of the cancellation effect between mutually opposite orbital current field HL and the Fermi contact field HD. It is notable that, as the temperature decreases below the Néel temperature, both quadrupole shift and asymmetrical line broadening appear and increase with decreasing temperature, suggesting the presence of an electric-field gradient and accompanying relaxation effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352406
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  • 5
    Electronic Resource
    Electronic Resource
    Influence of La defect on the magnetoresistance and magnetic properties of La1−xMnO3 (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 7416-7418 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Influence of the effect of lanthanum deficiency on the structural, magnetoresistance, and magnetic properties have been studied on a series of La1−xMnO3 (x=0, 0.05, 0.1, 0.2, and 0.33) powder samples. The powder samples were prepared by the sol–gel method. The x-ray diffraction analyses of the samples revealed a single phase of rhombohedral symmetry. Magnetization curves showed a weak ferromagnetic ordering for the sample x=0.0 with its Curie TC=138 K, but for the other samples showed ferromagnetic phase. The Curie temperature TC, with increasing deficiency from x=0.05 to x=0.33, was found to be increased from 272 to 279 K, respectively. The saturation magnetic moments per Mn atom at 80 K for x=0.0 and 0.10 are 2.30, 3.21 μB, respectively. A small increasing La defects resulted in changes of their magnetic structures thoroughly. In all the La defect samples, the temperature dependence of resistance shows that metal to insulator transition occurs near the TC and is closely related to the magnetization. The magnetoresistance value of 30% [Δρ/ρ(0)] has been obtained at 272 K under H=1.5 T for the sample x=0.1. The evidence for the formation of double exchange is also shown in x-ray measurements. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1362652
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  • 6
    Electronic Resource
    Electronic Resource
    Anisotropic hyperfine field fluctuation in Sr2FeMoO6 (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 7681-7683 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The double perovskite Sr2FeMoO6 has been studied by the Mössbauer technique, neutron, and x-ray diffraction. The structure is found to be tetragonal with lattice constants a0=5.5729 Å and c0=7.9077 Å. Mössbauer spectra and neutron diffraction measurements of Sr2FeMoO6 have been taken at various temperatures ranging from 10 to 473 K. The low-field magnetoresistance magnitude (Δρ/ρ0) at 500 Oe was 3.1% and 1.8% at 77 and 300 K, respectively. As the temperature increases toward to the Curie temperature, TC=425 K. Mössbauer spectra show the line broadening and 1, 6 and 3, 4 linewidth difference because of anisotropic hyperfine field fluctuation. The anisotropic field fluctuation of +H(P+=0.85) was great than −H(P−=0.15). We also calculated frequency factor and anisotropy energy with values of 9.8 Γ/(h-dash-bar) and 149.6 erg/cm3, respectively, using the relatively accurate data for T=260 K which is associated with the large line broadening. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1362654
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  • 7
    Electronic Resource
    Electronic Resource
    Magnetic properties of Nd1/3Sr2/3FeO3 by neutron and Mössbauer spectroscopy (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 7344-7346 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Charge transfer type Nd1/3Sr2/3FeO3 was synthesized and its magnetic properties were investigated by neutron diffraction and Mössbauer spectroscopy at various temperatures ranging from 4.2 K to room temperature. The powder neutron diffraction shows magnetic ordering structures. The Nd1/3Sr2/3FeO3 with small lattice distortion underwent a charge ordering (CO) phase transition at and below TCO=163 K corresponding to a sequence of Fe+3Fe+3Fe+5Fe+3Fe+3Fe+5 aligned along the z direction of rhombohedral, as well as canted antiferromagnetic spin ordering. The spin rotation resulting from helical spin of Nd was observed at and below 25 K. At 4.2 K, the electric quadrupole splittings for Fe3+ and Fe5+ are 0.06 and 0.15 (mm/s) which were changed to −0.06 and −0.02 (mm/s) at and above 20 K. It is evidence of spin rotation in Nd1/3Sr2/3FeO3. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1361265
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  • 8
    Electronic Resource
    Electronic Resource
    Mössbauer studies of BaFe11.9Mn0.1O19 by a sol–gel method (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 6244-6246 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: BaFe11.9Mn0.1O19 powders were prepared by a sol–gel method. Magnetic and structural properties of the powders were characterized by Mössbauer spectroscopy, x-ray diffractometry, and vibrating sample magnetometry. X-ray diffraction and Mössbauer measurements showed that the BaFe11.9Mn0.1O19 had an M-type hexagonal structure with a0=5.900 Å and c0=23.219 Å. Mössbauer spectroscopy was performed at various temperatures ranging from 13 to 800 K, and each spectrum for a temperature below the Curie temperature (TC=775±5 K) was fitted with five subspectra of Fe sites in the structure (4fVI, 2a, 4fIV, 12k, and 2b). The area fractions of the subspectra at 13 K were 18.0%, 10.2%, 17.5%, 46.1%, and 8.2%, respectively. The 2b site had a very large quadrupole splitting. The isomer shifts indicated that the valence state of the Fe ions was ferric (Fe3+). The saturation magnetization Ms was 58 emu/g, and coercivity Hc was 5141 Oe at room temperature under an applied field of 15 kOe. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372668
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  • 9
    Electronic Resource
    Electronic Resource
    Magnetic properties of sol-gel derived Ni–Zn ferrite thin films on yttria stabilized zirconia buffered Si(100) (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 5226-5228 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of yttria stabilized zirconia (YSZ) buffer layers for the sol-gel derived Ni–Zn ferrite thin films on SiO2/Si(100) substrates were investigated. The 500 Å thick YSZ buffer layers were found to effectively suppress the diffusion of Si into the ferrite thin films. As a consequence, films with lower Hc and higher Ms could be obtained by annealing at higher temperature (900 °C), which was not accomplished in the films without the buffer layer due to the Si diffusion. The angular variation of Hc with respect to the direction of applied field shows that a films without the buffer layers deviates more from the domain wall motion, thus, the diffused Si was suggested to segregate at the grain boundaries of the ferrite film and to reduce the intergranular exchange coupling. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369951
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  • 10
    Electronic Resource
    Electronic Resource
    Crystallographic and magnetic properties of NdFe10.7TiM0.3(M=B, Ti) : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5516-5518 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: NdFe10.7TiM0.3(M=B, Ti) has been studied with x-ray diffraction, Mössbauer spectroscopy, and a vibrating sample magnetometer. The alloys were prepared by arc-melting under an argon atmosphere. The NdFe10.7TiB0.3 exhibits a pure single phase, whereas the NdFe10.7Ti1.3 contains some α-Fe, from x-ray and Mössbauer measurements. The NdFe10.7TiB0.3 has the ThMn12-type tetragonal structure with a0=8.587 A(ring) and c0=4.788 A(ring). The Curie temperature (TC) is 570 K from Mössbauer spectroscopy performed at various temperatures ranging from 13 to 770 K. Each spectrum below TC was fitted with five subspectra of Fe sites in the structure (8i1, 8i2, 8j1, 8j2, and 8f ). The area fraction of the subspectra at room temperature are 16.4%, 8.2%, 14.8%, 21.3%, and 39.3%, respectively. Magnetic hyperfine fields for the Fe sites decrease on the order of Hhf(8i)(approximately-greater-than)Hhf(8j)(approximately-greater-than)Hhf(8f ). The average hyperfine field Hhf(T) of the NdFe10.7TiB0.3 shows a temperature dependence of [Hhf(T)−Hhf(O)]/Hhf(O)=−0.39(T/TC)3/2 & −0.17(T/TC)5/2 for T/TC〈0.7, indicative of spin-wave excitation. Annealing the alloy at around TC for 60 min resulted in a two phase microstructure consisting of a ThMn12-type structure and α-Fe. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361851
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