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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 4366-4372 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A systematic investigation of crystallographic and magnetic properties of nitride R3Fe29−xCrxN4 (R=Y, Ce, Nd, Sm, Gd, Tb, and Dy) has been performed. The lattice constants and unit cell volume decrease with increasing rare earth atomic number from Nd to Dy, reflecting the lanthanide contraction. After nitrogenation the relative volume expansion of each nitride is around between 5% and 7%. The nitrogenation results in a good improvement in the Curie temperature, the saturation magnetization and anisotropy fields at 4.2 K, and room temperature for R3Fe29−xCrxN4. Magnetohistory effects of R3Fe29−xCrxN4 and R3Fe29−xCrx (R=Nd and Sm) are observed in a low field of 0.04 T. First order magnetization process occurs in Sm3Fe24.0Cr5.0N4 in magnetic fields of 2.8 T at 4.2 K. After nitrogenation, the easy magnetization direction of Sm3Fe24.0Cr5.0 is changed from the easy-cone structure to the uniaxial. The good intrinsic magnetic properties of Sm3Fe24.0Cr5.0N4 make this compound a hopeful candidate for new high-performance hard magnets. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 7450-7457 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A systematic investigation of structure and intrinsic magnetic properties of the novel compounds R3(Fe, T)29 (R=Y, Ce, Nd, Sm, Gd, Tb, and Dy; T=V and Cr) has been performed. The lattice constants and unit cell volume decrease with increasing the rare-earth atomic number from R=Nd to Dy, except for Ce, reflecting the lanthanide contraction. The Curie temperature increases from R=Ce to Gd and decreases from Gd to Dy, respectively, with increasing atomic number and Gd3Fe29−xTx has the highest Curie temperature for each series of R3Fe29−xTx (T=V or Cr) compounds. The saturation magnetization of R3Fe29−xTx at 4.2 K decreases gradually from R=Nd to Dy with increasing atomic number, except for Ce, in each series of R3Fe29−xTx. It is suggested that the Ce ion in Ce3Fe29−xTx is valence fluctuated which leads to the unusual magnetic properties. The spin reorientations of the easy magnetization direction of R3Fe29−xTx are observed at around 230, 230, and 160 K for R=Nd, Sm, and Tb when T=V, and at around 230 and 180 K for R=Nd and Tb when T=Cr, respectively. First order magnetization processes are observed around 5.7 T for Sm3Fe26.7V2.3 and 4 T for Sm3Fe24.0Cr5.0 at 4.2 K, 2.0 T for Tb3Fe28.0V1.0, and 2.3 T for Tb3Fe28.0Cr1.0 at room temperature. A phenomenological analysis shows that the saturation magnetization of R3Fe29−xTx compounds with a low T concentration can be roughly calculated based on a combination of those of the 2:17R and 1:12 units in a ratio of 1:1. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 2012-2015 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Structure and magnetic properties of the R2Fe17-based quasiternary compounds (R=Sm, Er, Gd, Y, Pr, Nd; M=Al, Ga) and their nitrides have been investigated. The saturation magnetization of R2Fe17−xMx compounds decreases with the increasing M content, while the M concentration dependence of the Curie temperature exhibits a maximum at about x=3.0 for the parent compounds. By nitrogenation the lattice parameters, the saturation magnetization, and the Curie temperature all have a corresponding increase compared with the parent alloys. The volume effects on the Curie temperature of these compounds have been studied. The d ln Tc/d ln V values were derived by comparing the change of the Curie temperature and volume before and after nitrogenation and show a linear dependence on the Curie temperatures for these systems investigated. This behavior can be quite well understood in terms of a combined model of localized and itinerant electrons suggesting more than 90% d electrons are localized, The same conclusion can be obtained from a analysis of the exchange field Hex dependence of the iron sublattice magnetization in the R2Fe17 compounds and their nitrides, and the iron proportionality constant VFe before and after nitrogenation. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 2533-2535 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetoelectric properties of the tunnel junctions, Al(50 nm)/Al2O3(1.2 nm)/Al(50 nm) (x=0), Al(55 nm)/Al2O3(1.0 nm)/Co(55 nm) (x=0 and top electrode is Co), and Al1−xCox(55 nm)/Al1−xCox-oxide(d nm)/Al(55 nm) (x=0.25, 0.50, 0.75, and 1.0), were investigated. Oxides of Al1−xCox (x=0, 0.25, 0.50, 0.75, and 1.0) were chosen as barrier materials in order to modulate the magnon and phonon excitations in the barrier layer and the interfaces. It was shown that the magnon and phonon excitations were the main sources of inelastic scattering in the tunneling processes for the conduction electrons in these tunnel junctions at nonzero bias voltages. The magnon effects were enhanced in the Co-rich barrier junctions. The Al–O–Co phonon energy decreased with increasing Co composition between the Al–O and Co–O phonon energies based on an Al–O–Co stretching mode in the Al1−xCox-oxide barrier as vibrational frequency of crystal lattice decreased with increasing Co composition. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 283-285 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Temperature dependence of tunnel magnetoresistance (TMR) ratio, resistance, and coercivity from 4.2 K to room temperature and applied voltage dependence of the TMR ratio and resistance at room temperature for a tunnel junction, Ta (5 nm)/Ni79Fe21 (3 nm)/Cu (20 nm)/Ni79Fe21 (3 nm)/Ir22Mn78 (10 nm)/Co75Fe25 (4 nm)/Al (0.8 nm)-oxide/Co75Fe25 (4 nm)/Ni79Fe21 (20 nm)/Ta(5 nm), were investigated. TMR ratio, effective barrier height and width, and breakdown voltage of the junction can be remarkably enhanced after annealing at 300 °C for an hour. High TMR ratio of 49.7% at room temperature and 69.1% at 4.2 K were observed. The value of spin polarization of Co75Fe25, P=50.7%, deduced from the TMR ratio at 4.2 K was corresponding well to the experimental data measured at 0.2 K in a spin polarized tunneling experiment using a superconductor/insulator/ferromagnet tunneling junction. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 3248-3252 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A systematic investigation of the structure and magnetic properties of novel compounds Tb3(Fe1−xVx)29 (x=0.033, 0.044, 0.056, and 0.061) has been performed. The lattice parameters and Curie temperatures are obtained. The saturation magnetization of Tb3(Fe1−xVx)29 decreases but the anisotropy field increases linearly with increasing V concentration at 4.2 K and room temperature. The spin reorientations of the easy magnetization direction of Tb3(Fe1−xVx)29 occur at around 160 K. A first order magnetization process of Tb3(Fe1−xVx)29 is observed with magnetic field in the range between 2.0 and 1.6 T at room temperature. The saturation magnetization of Tb3Fe29−yVy with a low V concentration at 4.2 K can be roughly calculated based on a combination of that of the Tb2Fe17 and TbFe12−yVy units in a ratio of 1:1. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Mössbauer spectra for Fe atoms in the series of R3Fe29-xVx (R = Y, Ce, Nd, Sm, Gd, Tb, and Dy) compounds were collected at 4.2 K. The ratio of 14.5 T/μB between the average hyperfine field Bhf and the average Fe magnetic moment μ Fe MS , obtained from our data, in Y3Fe29-xVx is in agreement with that deduced from the RxTy alloys by Gubbens et al. The average Fe magnetic moments μ Fe MS in these compounds at 4.2 K, deduced from our Mössbauer spectroscopic studies, are in accord with the results of magnetization measurement. The average hyperfine field of the Fe sites for R3Fe29-xVx at 4.2 K increases with increasing values of the rare earth effective spin (gj-1)J, which indicates that there exists a transferred spin polarization induced by the neighboring rare earth atom.
    Type of Medium: Electronic Resource
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