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  • 1
    Electronic Resource
    Electronic Resource
    Magnetotransport in magnetic epitaxial metal layers buried in (Ga,Al)As heterostructures (invited) (abstract) : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6117-6117 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Incorporation of magnetic, metallic quantum wells in semiconductors has added new dimensions to epitaxial heterostructures. Magnetotransport experiments explore the interplay of bandstructure, quantum confinement, dimensionality and magnetism. Rare earth monoarsenides, like ErAs, have been grown as buried layers in GaAs. The material is a semimetallic antiferromagnet that exhibits spin-disorder scattering at the Néel point. By diluting the ErAs with ScAs, lattice matching to GaAs can be achieved and these materials exhibit Shubnikov–de Haas (SdH) oscillations. The exchange interaction between the conduction band and the 4f spin deduced from SdH agrees with that derived from spin-disorder scattering. Surprisingly, down to 2 monolayers, quantum confinement does not convert the semimetal into a semiconductor. This is not understood. But, the Neel point can be seen to drop by a factor of two by following the spin-disorder scattering. In the few monolayer regime the magnetotransport can change its character and is more aptly described by bound magnetic polarons. More recently, ferromagnetic, metastable, τ-MnAl layers have also been grown on GaAs. Thin layers of τ-MnAl grow in such a way that the tetragonal axis is perpendicular to the interface. The extraordinary Hall effect and longitudinal magnetotransport confirm that the moment has the desired property of being oriented perpendicular to the interface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347785
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  • 2
    Electronic Resource
    Electronic Resource
    Epitaxial relations between in situ superconducting YBa2Cu3O7−x thin films and BaTiO3/MgAl2O4/Si substrates (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 1772-1776 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In situ superconducting YBa2Cu3O7−x films with Tc0 up to 87 K and Jc, 77 K up to 6×104 A/cm2 were prepared on Si substrates with MgAl2O4 and BaTiO3 double-buffer layers. The epitaxial relations between various layers were established by transmission electron microscopy. The MgAl2O4 layer is heavily faulted. The subsequent BaTiO3 layer stops most of the faults, provides a template for the YBa2Cu3O7−x growth, and partially screens off the stress due to different thermal expansion coefficients. The microstructure of the YBa2Cu3O7−x layer is very similar to that of the films deposited directly on SrTiO3, exhibiting a homogeneous heavily faulted single-crystal-like structure free from secondary phases and grain boundaries. The slight degradation of the transport properties is attributed to residual thermal stress.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346607
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  • 3
    Electronic Resource
    Electronic Resource
    A microstructure based magnetization reversal model in sintered Fe-Nd-B magnets. II. Effect of post sintering treatments (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 5772-5777 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of post sintering heat treatments on the intrinsic coercivity of Fe-Nd-B magnets is studied. It is shown that the large anisotropy in thermal expansion coefficients in the a and c directions of the tetragonal unit cell as well as the anisotropy in thermal expansion properties between the matrix and the grain boundary phase, will lead to stresses upon quenching from the sintering temperature. The effect of stresses due to water quenching have been incorporated into the model developed in the companion paper (Part I). This quenching stress manifests itself as a stress anisotropy constant, which opposes the magnetocrystalline anisotropy constant. Thus, the effective anisotropy field, near the interfaces, is reduced from its value in an optimally cooled sample, leading to a lower iHc. It is also shown through step quenching experiments that the effect of quenching stresses can be nullified by cooling slowly to below a specific temperature following which quenching does not influence the intrinsic coercivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346946
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  • 4
    Electronic Resource
    Electronic Resource
    The extraordinary Hall effect in coherent epitaxial τ (Mn,Ni)Al thin films on GaAs : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6399-6401 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ultrathin coherent epitaxial films of ferromagnetic τ(Mn,Ni)0.60Al0.40 have been grown by molecular beam epitaxy on GaAs substrates. X-ray scattering and cross-sectional transmission electron microscopy measurements confirm that the c axis of the tetragonal τ unit cell is aligned normal to the (001) GaAs substrate. Measurements of the extraordinary Hall effect (EHE) show that the films are perpendicularly magnetized, exhibiting EHE resistivities saturating in the range of 3.3–7.1 μΩ-cm at room temperature. These values of EHE resistivity correspond to signals as large as +7 and −7 mV for the two magnetic states of the film with a measurement current of 1 mA. Switching between the two magnetic states is found to occur at distinct field values that depend on the previously applied maximum field. These observations suggest that the films are magnetically uniform. As such, τ(Mn,Ni)Al films may be an excellent medium for high-density storage of binary information.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352609
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  • 5
    Electronic Resource
    Electronic Resource
    A microstructure based magnetization reversal model in sintered Fe-Nd-B magnets. I (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 5767-5771 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A microstructure based magnetization reversal model is presented for sintered Fe-Nd-B magnets. The model makes use of a position dependent domain wall energy profile to correlate the intrinsic coercivity, iHc (and the nucleation field) to the magnetocrystalline anisotropy field. The inferences of the model are verified through the study of the effect of Dy and Ce additions on the iHc as well as by examining the temperature dependence of iHc and anisotropy field existing in published literature. It is inferred from this model that selective modifications of the interfaces could lead to appreciable improvements in the magnetic properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346945
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  • 6
    Electronic Resource
    Electronic Resource
    Galvanomagnetic properties of epitaxial MnAl films on GaAs : 35th Annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 4689-4691 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Single-crystal films of τ-MnAl are grown by molecular-beam epitaxy on GaAs substrates. The extraordinary Hall effect shows a large hysteresis loop, and the magnetization is found to have a substantial component perpendicular to the plane of the film.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348298
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  • 7
    Electronic Resource
    Electronic Resource
    Thickness dependence of structural and electrical properties in epitaxial lead zirconate titanate films (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 595-602 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the effect of misfit strain on the microstructure and properties of ferroelectric lead zirconate titanate thin films. We have changed the misfit strain by varying the film thickness and studied the thickness effect on the domain formation of epitaxial PbZr0.2Ti0.8O3 (PZT) films grown by pulsed laser deposition on (001) LaAlO3 substrates with La0.5Sr0.5CoO3 (LSCO) electrodes. The nominal thickness of the PZT films was varied from 60 to 400 nm with the LSCO electrode thickness kept constant at 50 nm. X-ray diffraction experiments show that the films relax via the formation of a domains, the fraction of which increase with the ferroelectric film thickness. The c-axis lattice constant of PZT films calculated from the 002 reflection decreases with increasing film thickness and approaches the bulk value of ∼0.413 nm in the films thicker than 300 nm. Cross-sectional transmission electron microscopy images reveal that the a-domain fraction and period increase with increasing film thickness. The relaxation of misfit strain in the film is accompanied by systematic changes in the polarization properties, as well as the switching fields, quantified by the coercive field and the activation field. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370772
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  • 8
    Electronic Resource
    Electronic Resource
    Ferromagnetic antiresonance in La0.7Ba0.3MnO3 traced out by temperature variation : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 5157-5158 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using the phenomenon of ferromagnetic antiresonance (FMAR) in ceramic samples of La0.67Ba0.33MnO3 at 10 GHz, we report a large magneto-impedance MI=Rs(H(parallel))−Rs(H⊥)]/Rs(H(parallel)), where Rs is the microwave surface resistance and H the applied field. The MI reaches 30% at a field of 30 mT near room temperature. The FMAR also lets us measure M(T) by following Rs as a function of T and H. ©1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365154
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  • 9
    Electronic Resource
    Electronic Resource
    Response to an electric field of Nd0.7Sr0.3MnO3 films in a MOSFET configuration (abstract) : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4545-4545 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of an electric field on GMR oxide films was studied in a MOSFET configuration where the gate dielectric was a layer of SrTiO3 epitaxially grown on an underlying layer of the manganate which served as the source/drain. The response of the manganate channel was studied for different gate voltages. The following significant features were observed. The peak resistance temperature shifted to lower temperature for both polarities of the field. The resistance change varied quadratically with the field indicating the dominance of strain or polarization effects. In dynamical studies of the system using the gate voltage as an excitation the system showed anomalous slowing down near the peak of the resistivity. These results are understood on the basis of a stress effect on the film due to electro-elastic effects in the SrTiO3 layer, which introduces a tensile stress in the manganate layer upon the application of a gate voltage. The anomalous slowing down of the system near the ferromagnetic phase transition suggests a strong coupling between the spins, transport and structural distortions in the system. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361718
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  • 10
    Electronic Resource
    Electronic Resource
    ac-susceptibility studies on Zr1−xHoxCo2 [0≤x≤1] system and their hydrides (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 2090-2093 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The ac-susceptibility studies were carried out on the intermetallic compounds Zr1−xHoxCo2 [0≤x≤1] in the temperature range 13–300 K. The magnetic transition is found to be of the first-order type for HoCo2 (x=1.0) and second-order type for x=0.4–0.9. No magnetic ordering is observed for x=0.2 down to 13 K and x=0.0 is found to be Pauli paramagnetic. The magnetic ordering temperature (TC) increases from about 13 K for x=0.4 to 77 K for x=1.0. In addition, spin reorientation transitions are observed for x=0.9 and 1.0. On hydrogenation, TC is found to decrease considerably in all compounds. Hydrogen absorption in these compounds is found to weaken the exchange interactions which can be attributed to charge transfer effects. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358851
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