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  • 1
    Electronic Resource
    Electronic Resource
    Spin polarized tunneling in reactively sputtered tunnel junctions : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 5523-5525 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In order to study spin-polarized electron tunneling, we have grown MOM junctions where M is a magnetic transition metal (Co, Fe or CoFe) and O a reactively sputtered oxide (CoO, NiO, Ta2O5, MgO, HfO2). The oxide thickness ranged between 20 and 300 Å. The structural, magnetic, and transport properties of these junctions have been investigated. Among these various oxides, large magnetoresistance due to spin-polarized tunneling effects have been observed in MgO on the order of 20% at 77 K, and a maximum of 31% has been observed in HfO2 based junctions at 30 K. The other oxides had a much higher tendency to form pinholes and had smaller dielectric breakdown thresholds. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364590
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  • 2
    Electronic Resource
    Electronic Resource
    Anisotropy and angular variation of the giant magnetoresistance in magnetic multilayers (invited) : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 6370-6375 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The giant magnetoresistance (GMR) of magnetic multilayers is usually considered as isotropic, i.e., independent of the direction of the sensing current with respect to the applied field. In spin-valve samples of the form NiFe/Cu/NiFe/FeMn it is possible to accurately determine the amplitude of the GMR (without any contribution from the usual anisotropic magnetoresistance) for various direction of the current with respect to the direction of the magnetization of the two ferromagnetic layers, both in the parallel and antiparallel magnetic configurations. In three series of spin-valve samples of the composition F tF/Cu tCu/NiFe/FeMn, we have observed that the GMR amplitude is larger when the current is perpendicular to the magnetizations than when it is parallel to it. This intrinsic anisotropy in the GMR shows a pronounced maximum (relative amplitude of the anisotropy of the order of 10% at the maximum) for a thickness of the ferromagnetic layer of the order of 150 A(ring). In contrast, this anisotropy depends very weakly on the nonmagnetic spacer layer thickness. The results are compared with semiclassical calculations of Rijks et al. [Phys. Rev. B 51, 283 (1995)]. On another respect, we have measured the in-plane (CIP) and perpendicular to the plane (CPP) giant magnetoresistance of antiferromagnetically coupled (NiFe/Ag) multilayers. Particular attention has been paid on the variation of resistivity with the angle Δθ between the magnetization in the successive magnetic layers. While the CIP GMR varies almost linearly with cos(Δθ), the CPP GMR shows strong deviations from linearity especially at large NiFe thicknesses. The results are discussed in terms of relative role of s-like and d-like electrons in CIP and CPP transport. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362003
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of scattering at lateral edges on the current-perpendicular-to plane giant magnetoresistance of submicronic pillars (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 7302-7304 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: From a phenomenological point of view, we have investigated the effect of scattering at lateral edges on the current-perpendicular-to-plane (CPP) transport properties of submicronic magnetic multilayer pillars. This scattering can be considered as a current-in-plane contribution in the CPP geometry. As a first attempt to calculate the CPP resistance and GMR in this situation, we have combined the serial resistance network model of CPP transport with an exponential variation of the local conductivity as a function of the distance from the edges of the pillars assuming that the scattering is perfectly diffusive at the edges of the pillars. As the lateral size of the pillars decreases below 100 nm, it is shown that this scattering leads to a strong increase in the CPP resistivity as well as a decrease in both ΔR/R and ΔR* area. Furthermore, due to the difference in mean-free paths from layer to layer, the current lines are no longer uniform in the pillar even if the latter is the shape of an infinite cylinder. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1357852
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of interfacial specular electron reflection on the anisotropic magnetoresistance of magnetic thin films (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 4140-4145 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigated the effect of specular reflection on the anisotropic magnetoresistance (AMR) of magnetic thin films. The sheet conductance is calculated as a function of the angle between magnetization and current from the microscopic transport parameters by using an extension of the Fuchs–Sondheimer theory. The calculation combines specular reflection on the film interfaces with mean-free paths which depend on the angle between the local magnetization and the electron velocity. The theoretical results are compared with experimental ones. Specular reflection can explain the quite large AMR amplitude observed in thin NiFe films used in the last generation of AMR heads. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1310189
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  • 5
    Electronic Resource
    Electronic Resource
    Quantitative interpretation of the magnetoresistive response (amplitude and shape) of spin valves with synthetic antiferromagnetic pinned layers (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 3415-3420 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present an analytical calculation of the shape of the magnetoresistive response of spin-valve structures with synthetic antiferromagnetic pinned layer, i.e., of the form buffer/ferromagnet1/Cu/ferromagnet2/Ru/ferromagnet3/antiferromagnet. The magnetization reversal in the three magnetic layers is assumed to occur via coherent rotation. An analytical expression of the whole hysteresis loop is given as a function of the characteristic parameters of the system (coupling strength through the Ru spacer, ferromagnet3/antiferromagnet pinning energy). We also extended a code based on the Boltzmann equation of transport to calculate the giant magnetoresistance (GMR) amplitude in these structures from the microscopic transport parameters. In order to explain the relatively high GMR amplitude experimentally observed in such spin valves, it is shown that some degree of specular reflection must be introduced at the ferromagnet2/Ru interface. Good agreement with both the shape and amplitude of the experimental magnetoresistance curves can be obtained. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372360
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  • 6
    Electronic Resource
    Electronic Resource
    Influence of deposition angle on the properties of NiO spin-valves (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 1436-1443 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Bottom and top spin-valves comprising NiO as pinning layer were prepared by depositing the NiO layer either at normal or oblique incidence onto Si/SiO2 substrates. When the NiO layer is deposited at oblique incidence, a strong uniaxial anisotropy is observed in the hysteresis loop of the Co layer which is exchange coupled to this layer. The easy axis is perpendicular to the plane of incidence. In contrast, when the NiO layer is deposited at normal incidence, the hysteresis loops of the exchange coupled Co layer show an in-plane isotropy. The uniaxial anisotropy observed after oblique incidence deposition is ascribed to growth-induced uniaxial strain and magnetoelastic effects in the NiO antiferromagnetic layer. It is observed that after annealing under a magnetic field, Co/NiO bilayers in which the NiO has been deposited at oblique incidence exhibit symmetric hysteresis loops whereas similar bilayers in which the NiO has been deposited at normal incidence exhibit shifted hysteresis loops. This effect is related to a difference in grain size between these systems. Furthermore, bottom and top spin-valves in both of which the NiO has been deposited at oblique incidence are compared. In contrast to the bottom spin-valves, the top spin-valves exhibit shifted hysteresis loops after annealing from the NiO Néel temperature (520 K) under a magnetic field. It is shown that this difference is due to structural defects in the bulk of the NiO layer for bottom spin-valves which do not exist in top spin-valves. These defects tend to disrupt the exchange interactions within the NiO thickness thus reducing the pinning energy of this layer. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1428098
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  • 7
    Electronic Resource
    Electronic Resource
    Magnetization processes in amorphous R-Co/R'-Co/R-Co sandwiches (R, R'=Y, Nd, Gd, Er) (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5677-5679 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Sandwiches consisting of three amorphous layers (R0.33,Co0.67)1000 A(ring)/ R'0.33,Co0.67)1000 A(ring)/ (R0.33Co0.67)1000 A(ring), have been prepared by dc triode sputtering (R, R' are rare-earth elements). The systems chosen are such that the bulk magnetization alternates from one layer to the next or the coercivity of each layer is significantly different. Magnetic transitions are observed under field. They have been quantitatively analyzed in terms of successive reversals of magnetization in the different layers. The creation or annihilation of planar Bloch walls parallel to the surface are associated with the magnetic transitions. The wall energy and wall width depend essentially on the competition between exchange energy and Zeeman energy. It is suggested that the existence of such Bloch walls may favor magnetization reversal in thin films by coherent processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345924
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  • 8
    Electronic Resource
    Electronic Resource
    Some properties of 2π Néel walls and Néel points in the XY model : 35 th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5959-5961 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The properties of two types of topological defects in the 2D classical XY model, Néel lines and Néel points, have been investigated via numerical simulation. The effect of a symmetry-breaking magnetic field has been considered. For cyclic boundary conditions a uniform array of line defects can be stabilized. Along a line defect, point defects can be introduced as spatial changes of chirality of the wall. These point defects consist of pairs of bound vortices of the same sign. When several such point defects are introduced on a given line defect, they also tend toward uniform spacing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347829
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  • 9
    Electronic Resource
    Electronic Resource
    Magnetotransport properties of magnetically soft spin-valve structures (invited) : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 4774-4779 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic and magnetotransport properties of several series of sandwiches consisting of two ferromagnetic layers (Ni, Co, Ni80Fe20) separated by a noble metal (Cu, Ag, Au) are described. In order to vary the relative orientation of the magnetizations of the two ferromagnets, one of them was constrained by exchange anisotropy (e.g., NiFe/Fe50Mn50). The ferromagnetic layers are magnetically soft and not coupled antiparallel, giving very large changes of resistance at low fields. At room temperature relative changes ΔR/R of 4.1% in 10 Oe for Si/Ta 50 A(ring)/NiFe 62 A(ring)/Cu 22 A(ring)/NiFe 40 A(ring)/FeMn 70 A(ring)/Ta 50 A(ring) and 8.7% in 20 Oe has been obtained for a structure based on Co/Cu/Co layers. The magnetoresistance versus the thickness of the ferromagnetic layer shows a broad peak near 80 A(ring) for Ni, Co and NiFe, demonstrating the importance of bulk rather than interfacial spin-dependent scattering, in contrast to Fe/Cr multilayers. The magnetoresistance decreases exponentially with increasing interlayer (Cu and Au) thickness, indicating that the magnetoresistance is due to the exchange of polarized electrons from one ferromagnetic layer to the other. The variation with Ag interlayer thickness is different for structural reasons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348252
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  • 10
    Electronic Resource
    Electronic Resource
    Rotational and transverse dynamics of some random anisotropy magnets (invited) (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5763-5768 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: After rapid survey of the behavior of random anisotropy magnets, the time and frequency evolution of the magnetization vector of a rotating disk of amorphous DyNi is focused on, as measured by a two-SQUID detectors setup. The results show that the dynamics of this system is completely determined by two macroscopic variables: the magnetizations M1 and M2, respectively associated with short and long relaxation times. The first one is fixed with respect to the applied field and therefore responsible for dissipation (magnetic friction) whereas the second one is fixed with respect to the sample (rotating anisotropy). Furthermore, transverse ac susceptibility experiments are used to confirm some of the results obtained. In particular low-temperature dynamical scaling (T→0) permits the existence of a new type of frequency crossover, when the volume samples by the ac field becomes of the order of Imry and Ma domains, to be shown.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345958
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