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  • 1
    Electronic Resource
    Electronic Resource
    Structural and magnetic characterization of amorphous Gd2Fe14B thin films : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6491-6493 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin amorphous films of nominal composition Gd2Fe14B were fabricated on Si (100) substrates using ion-beam sputtering for the purpose of establishing their structural and magnetic properties at room temperature. X-ray-diffraction scans performed on as-deposited and annealed films revealed an amorphous structure. The as-deposited saturation magnetization was found to be 8101 G at room temperature suggesting ferrimagnetic ordering with anti-parallel coupling similar to other heavy rare earth-transition metal systems. Results from in-plane and perpendicular ferromagnetic resonance experiments conducted at 9.108 GHz showed the films to be inhomogeneous. This was evident from the presence of two in-plane resonance lines and spin-wave spectra that were not quadratic. Annealing at 300 °C for 30 min significantly reduced the absorption of the second in-plane resonance and restored classical n2 law spin-wave behavior. It is speculated that the origin of the inhomogeneities is due to the kinetics of the deposition process where the increased mobility of the condensing Fe atoms leads to interspersed amorphous regions which are rich in Fe and Gd, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352590
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  • 2
    Electronic Resource
    Electronic Resource
    Ferrimagnetic resonance lineshape asymmetry due to Suhl instabilities (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1938-1943 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present calculations of the ferrimagnetic resonance lineshapes resulting from second order Suhl instabilities for thin films and spheres. We find that whereas a spherical sample has a lineshape which is symmetrical around the resonant frequency, a thin film has an asymmetrical lineshape. The calculations are in agreement with measurements that we have performed of the lineshape as a function of input power for thin film samples of both barium ferrite and yttrium iron garnet. When the magnetic field direction is changed from perpendicular to parallel to the film plane, the asymmetry of the lineshape at magnetic resonance changes in opposite sense relative to the resonant field. Theoretical estimates of the critical microwave field necessary for second order Suhl instabilities to occur are in agreement with measured critical fields.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354777
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  • 3
    Electronic Resource
    Electronic Resource
    Epitaxial yttrium iron garnet films grown by pulsed laser deposition (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1242-1246 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial Y3Fe5O12 (YIG) films have been grown by the pulsed laser deposition (PLD) technique on (111) gadolinium gallium garnet substrates. The effect of substrate temperature and oxygen partial pressure on the structure, composition, and magnetic properties of the films was investigated and compared to liquid phase epitaxy YIG films. The results demonstrated that epitaxial YIG films could be prepared under a wide range of deposition conditions, but narrow linewidth (ΔH(approximately-equal-to)1 Oe) films were producible only at low oxygen partial pressures (O2〈250 mTorr) and relatively high substrate temperatures (Ts(approximately-greater-than)800 °C). Since the linewidth of single-crystal YIG is dominated by surface and volume defects and/or impurities, the narrow linewidth indicated that PLD is a viable technique for producing high-quality ferrite films for microwave device applications. In addition, under all deposition conditions (50–1000 mTorr and 700–850 °C) there is a uniaxial axis perpendicular to the film plane. However, at low oxygen pressure the uniaxial anisotropy energy constant Ku is negative while at high oxygen pressure Ku is positive.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354927
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  • 4
    Electronic Resource
    Electronic Resource
    Pulsed laser deposition of epitaxial BaFe12O19 thin films (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 5107-5110 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial thin films of barium hexaferrite (BaFe12O19) have been fabricated by the pulsed laser deposition technique on basal plane sapphire. Structural studies reveal the films to be predominantly single phase and crystalline, with the c axis oriented perpendicular to the film plane. The magnetic parameters deduced from vibrating sample magnetometer and ferromagnetic resonance (FMR) measurements are close to the parameters associated with bulk materials. Post annealing of the films reduced the FMR linewidth by more than a factor of 3 so that it compares reasonably well with single-crystal films. The derivative FMR linewidth was measured to be 66 Oe at 58 GHz and 54 Oe at 86 GHz. Spin-wave-like modes have been observed for the first time in barium ferrite films. The deduced exchange stiffness constant of 0.5×10−6 ergs/cm is in reasonable agreement with recent calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350614
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  • 5
    Electronic Resource
    Electronic Resource
    Zero magnetic field ferromagnetic resonance properties of single-crystal YIG/GGG/YIG layers : 35th annual conference on magnetism and magnetic materials San Diego, California (USA) 29 Oct − 1 Nov 1990 (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6212-6214 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This study is an extension of previous work dealing with single crystals of YIG/GGG/YIG grown in (110) layers. Ferromagnetic resonance (FMR) measurements for fields along the 〈111〉 axis were performed. The microwave measurements reveal hysteretic behavior as the FMR frequency is measured for positive and negative magnetic fields H. For H in which the magnetic moment is zero (spin flop) the FMR frequency goes through a discrete and measurable jump or change. This discontinuity in the FMR frequency at the spin-flop condition is attributed to the magnetostatic interaction between the two YIG layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348811
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  • 6
    Electronic Resource
    Electronic Resource
    Ferrimagnetic resonance linewidth in single-crystal Mn-doped Ba2Zn2Fe12O22 (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5524-5526 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The ferrimagnetic resonance linewidths in single crystals of Mn-doped Ba2Zn2Fe12O22 were measured as a function of frequency (0.01–40 GHz) and temperature (4–300 K). In addition, the saturation magnetization, g factor, and planar anistropy fields were measured. The field linewidth ΔH appears to scale with frequency; however, the field linewidth as a function of temperature for the hexaferrite exhibits maxima. The temperature-dependent resonant field values were used to calculate the anisotropy field as a function of temperature. These measurements were performed in a frequency-swept slot-coplanar device at a fixed value of applied magnetic field and in a traditional ferrimagnetic resonance system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345872
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  • 7
    Electronic Resource
    Electronic Resource
    Coefficients of thermal expansion for barium hexaferrite (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 3517-3520 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The thermal expansion coefficients along the a axis (αa) and c axis (αc) of barium hexaferrite were measured from room temperature to 850 °C. The thermal expansion of barium hexaferrite along the a axis and c axis was found to be linear as a function of temperature, indicating constant thermal expansion coefficients over this temperature range. The specific values for αc and αa were calculated to be 12.2±0.9 and 9.99±1.1 ppm/°C, respectively. The measurements were performed using a standard x-ray powder diffraction setup equipped with a high temperature stage. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361402
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  • 8
    Electronic Resource
    Electronic Resource
    CoFe2O4 thin films grown on (100) MgO substrates using pulsed laser deposition : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 6338-6340 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin films (≈0.4 μm) of cobalt ferrite (CoFe2O4) have been grown on single-crystal (100) MgO substrates using pulsed laser deposition (PLD). The phase, orientation, and microstructure of the as-deposited films were investigated as a function of substrate temperature (i.e., 200–800 °C) at a constant oxygen deposition pressure of 30 mTorr. The as-deposited films were found to be single phase, well oriented, and approximately matching the stoichiometry of the target, but the cubic lattice constant of the films depended on the substrate temperature indicating that the films were strained. The greatest effect of the substrate temperature was on the magnetic properties of the as-deposited films. At 800 °C, 4πMs was measured to be 5370 G which is approximately the accepted bulk value for cobalt ferrite. In addition, PLD cobalt ferrite films grown at substrate temperatures of 600 and 800 °C exhibited a uniaxial magnetic anisotropy with an easy direction normal to the film plane. Films grown at 200 and 400 °C also exhibited a uniaxial magnetic anisotropy but possessed a planar easy direction. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361991
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  • 9
    Electronic Resource
    Electronic Resource
    Anomalous Hall effect in Gd-doped La2/3Ca1/3MnO3 : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 4958-4960 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ceramic samples of composition (La1−xGdx)2/3Ca1/3MnO3 were prepared and used as targets to grow films onto LaAlO3 substrates by pulsed laser deposition. Comparison of the electrical resistance and thermopower, measured vs temperature and applied magnetic fields, indicates transport dominated by positively charged small polarons in the high temperature paramagnetic state. Nonetheless, the Hall effect, measured in 0.5 μm thick films of composition x=0 and x=0.25, has the sign that is normally ascribed to negatively charged free carriers. The magnitude of the Hall coefficient decreases exponentially with increasing temperature with an activation energy that differs from that of the resistivity. This behavior and its anomalous negative sign are interpreted to result from face-diagonal hopping of small polarons in the Mn sublattice. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365011
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  • 10
    Electronic Resource
    Electronic Resource
    Effects of defects on magnetoresistivity in La0.7Sr0.3MnO3 : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 4971-4973 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of structural and oxygen site defects on the ferromagnetic phase transition and magnetotransport in doped lanthanum manganite films have been examined. Oxygen defects were introduced through a vacuum annealing process while structural defects were introduced using ion irradiation. The introduction of both defect types strongly suppressed the Curie temperature Tc while increasing the peak resistivity, activation energy, and magnetoresistance ratio. For defect types leading to similar reductions in Tc, structural defects lead to a broader transition regime and a smaller MRR than are found for oxygen defects. Well above Tc both defect types lead to nearly identical resistivity curves. Structural defects are argued to primarily affect the carrier mobility, hence these data provide a clue that the carrier mobility is dominating the transport properties in this regime.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365016
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