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  • 1
    Electronic Resource
    Electronic Resource
    Magnetization reversal processes in Co-Re antiferromagnetically coupled multilayers: A magneto-optic and Monte Carlo study (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2692-2700 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A study of magnetization reversal processes in sputtered antiferromagnetically coupled (CotCoRe5 A(ring))×n multilayers, with n=2,3,5 is reported. The two components of the magnetization, parallel and perpendicular to the applied field are analyzed using a suitable transverse Kerr effect differential magneto-optical setup. At the remanent state, and for n=3, and 5, we obtain a magnetization of 1/3 and 1/5 of the saturation magnetization, respectively. This means that the magnetization in each layer is aligned parallel or antiparallel to the applied field direction. The observed perpendicular magnetization component is as expected, much smaller than the parallel magnetization component over the entire length of the hysteresis cycle. A Monte Carlo simulation was used to study the spin configurations in the individual layers as well as the type of magnetization hysteresis cycles. We find that the introduction of a small uniaxial anisotropy is needed to explain the observed multiloop structure in the n=3 multilayers. Within our model, spin-canting may occur within the ferromagnetic layers leading to particular remanent-state spin configurations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354663
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  • 2
    Electronic Resource
    Electronic Resource
    Magnetic and transport properties of sputtered Gd-Y multilayers : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 4532-4534 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Gd-Y-Gd multilayers were prepared that show a magnetoresistance enhancement for an Y layer separation of 30 A(ring). This magnetoresistance enhancement is an interface effect and occurs in samples where some degree of antiferromagnetic coupling is present.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348350
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  • 3
    Electronic Resource
    Electronic Resource
    Antiferromagnetic exchange and enhanced magnetoresistance in glass/ Fe50 A(ring)/Co11 A(ring)/CutCu/Co11 A(ring)/ Cu10 A(ring) structures : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5527-5529 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Glass/ Fe50 A(ring)/Co11 A(ring)/Cut/Co11 A(ring)/Cu10 A(ring) structures were sputtered in a high-vacuum system with a base pressure of 5×10−8 Torr. The magnetoresistance (MR) reaches 8% at room temperature for tCu=10 A(ring) with a saturation field of 700 Oe. For tCu=22 A(ring) the MR reaches 6.4% for a 200 Oe field. Our results are analyzed in a semiclassical approach by solving the Boltzmann equation for the five-layer structure with λCo=76 A(ring) and λCu=420 A(ring) and using both interfacial and bulk spin-dependent scattering. Interlayer coupling was checked by magneto-optical measurements using the transverse Kerr-effect geometry. For tCu=10 A(ring) we observe zero-remanence magnetization curves with saturation fields around 1 kOe. For tCu=22 A(ring) no evidence for macroscopic antiferromagnetic coupling is observed since the hysteresis cycle is almost square.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353691
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  • 4
    Electronic Resource
    Electronic Resource
    Structural characterization of Co-Re superlattices (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 7370-7373 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Co-Re superlattices were prepared with nominal periodicities of 65–67 A(ring) and varying bilayer composition. The structural characterization was made by x-ray diffraction and Rutherford backscattering spectrometry (RBS). First, second, and third order satellites are observed in the x-ray diffractogram at 2θ values and with intensities close to those predicted by simulation. This confirms the coherence of the superlattice. RBS measurements combined with RUMP simulations give information on interface sharpness and the absolute thicknesses of the Co and Re layers. Discrepancies between the experimental and simulated diffractograms are found for Co thicknesses below 18 A(ring).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349731
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  • 5
    Electronic Resource
    Electronic Resource
    Large magnetoresistance anisotropy in a new class of amorphous ferromagnets: U100−x−ySbxMny (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4901-4903 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: U100−x−ySbxMny amorphous ferromagnets were prepared that have an anisotropic magnetoresistance (AMR) as high as 9.3% at 15 K and a 2-T field. This is a striking result, since the AMR of typical amorphous ferromagnets does not exceed 1%. These materials are random anisotropy ferromagnets, with large coercive fields (Hc =1.2 T, 15 K) following a thermally activated regime at low temperature. The Curie temperatures range from 95 to 112 K. Resistivity values vary from 200 to 400 μΩ cm and the Hall angle can reach 20° at 15 K. For T〉TC, the resistivity follows a field-independent ln T behavior with dρ/dT showing a sharp anomaly at TC. Below TC, both these quantities are strongly anisotropic, depending on the angle between the magnetization and the current. Magnetization reversal process are inferred from the magnetoresistance hysteresis cycles—both coherent rotation and 180° domain-wall motion occur.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344725
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  • 6
    Electronic Resource
    Electronic Resource
    Antiferromagnetic coupling and magnetoresistance enhancement in Co-Re metallic superlattices (abstract) : The 5th Joint MMM−Intermag Conference (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 5878-5878 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Co-Re metallic superlattices were prepared that show antiferromagnetic exchange coupling and enhanced saturation magnetoresistance for particular values of the Re spacer thickness. We report studies on films with the structure glass /150 A(ring) Re/[13 A(ring)Co/tRe]16/50 A(ring) Re, with tRe ranging from 3 to 40 A(ring). These structures were grown by magnetron sputtering in a system with a base pressure of 1×10−7 Torr with deposition rates of 0.3 and 0.4 A(ring)/s for Co and Re, respectively. x-ray diffractograms indicate the structure to be highly textured with the c axis perpendicular to the sample plane. The superlattice structure was obtained from high-angle θ-2θ scans. First-, second-, and third-order satellites are observed on both sides of the central [002] peak. Periodicity and bilayer composition are obtained from comparison of the data with a theoretical calculation of the x-ray diffractogram. Thickness calibration was confirmed by Rutherford backscattering and profilometer data. In-plane magnetization and magnetoresistance data (Δρ/ρ) indicate that stronger antiferromagnetic coupling and highest Δρ/ρ occur for tRe≈6 A(ring). The saturation field (Hs) needed to align contiguous antiferromagnetically coupled Co layers is about 1 T. This corresponds to an exchange coupling between the Co layer J≈−1 erg/cm2. (Δρ/ρ) reaches 2% in samples deposited at 170 °C. This data confirms results obtained by Parkin et al.1 in Co-Ru and Co-Cr superlattices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350116
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  • 7
    Electronic Resource
    Electronic Resource
    Electrode roughness and interfacial mixing effects on the tunnel junction thermal stability (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 6650-6652 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The thermal stability of magnetic tunnel junctions with ultrathin (〈8 Å) Al2O3 barriers was studied and compared with 15 Å barriers. The tunnel magnetoresistance (TMR) decay cannot be explained only by Mn diffusion into the pinned CoFe layer since this diffusion starts above 300 °C independently of the barrier thickness, while the TMR degradation already occurs at 250–270 °C for the thinner barriers. The thermal stability is probably controlled by changes at the CoFe/Al2O3 interfaces and/or barrier structure. Structural analysis of 15 Å barriers after annealing at 435 °C, shows the existence of an interface region (8–12 Å thick) where CoFe and Al2O3 are found. This interfacial region can be explained by the increased roughness in the bottom electrode after annealing, as measured by atomic-force microscopy (from 1.5 to 4 Å). Ultrathin barriers show a similar trend. The use of low-resistance junctions using thin barriers requires good control of the roughness of the low-resistance bottom electrodes. This is done by preannealing and low-angle ion-beam smoothing 500-Å-thick Cu or Al films, which will then keep a roughness 〈2 Å during processing temperatures up to 400 °C. Low-resistance junctions (R×A∼40–60 Ω μm2) with 7 Å barriers grown on 600 Å Al buffers after the surface treatment show 25% TMR after annealing at 270 °C. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1359216
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  • 8
    Electronic Resource
    Electronic Resource
    Tunnel junctions with AlN barriers and FeTaN electrodes (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 6868-6870 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Tunnel junctions with AlN (AlNxOy) barriers and CoFe and FeTaN electrodes were studied. The AlN barrier was formed by nitridizing a 10 Å thick Al layer using radio frequency N2 plasma. The nitrogen and oxygen content in the barriers was determined by Rutherford backscattering spectroscopy (RBS) on specially prepared barriers deposited on DLC coated substrates. RBS results indicate less than 10% O2 incorporation in the barrier. Top-pinned junctions formed by nitridizing a 10 Å thick Al layer (CoFe electrodes) show resistance×area products from 73 Ω μm2 to 8.5 kΩ μm2 for increasing nitridation times from 30 to 200 s, with corresponding tunneling magnetoresistance (TMR) values from 13% to 33%. Bottom-pinned junctions with FeTaN electrodes were also fabricated. Maximum TMR signal is 17% after anneal at 225 °C for 30 min. In both cases (CoFe or FeTaN electrodes), TMR degrades for anneals above 250 °C. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1356714
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  • 9
    Electronic Resource
    Electronic Resource
    Exchange enhancement and thermal anneal in Mn76Ir24 bottom-pinned spin valves (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 6904-6906 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Exchange enhancement through thermal anneal in bottom-pinned Mn76Ir24 spin valves is investigated. Samples were fabricated by ion beam deposition (IBD), post-annealed in vacuum (10−6 Torr) at 270 °C for 10 min, then cooled in a 3 kOe applied field. For a bilayer structure, glass/Ta 40 Å/NiFe 30 Å/MnIr 60 Å/CoFe 25 Å/Ta 40 Å, the exchange field (Hex) reaches 1148 Oe (Jex=0.4 erg/cm2) after anneal. X-ray diffraction (XRD) analysis shows strong enhancement of 〈111〉 texture upon anneal, while grain size obtained from XRD and transmission electron microscopy for as-deposited and annealed states shows no major change. With increasing MnIr thickness, the exchange field decreases, and blocking temperature (Tb) increases, reaching 295 °C for tMnIr=180 Å. Spin valves built with the same exchange bilayer (Ta 20 Å/NiFe 30 Å/MnIr 60 Å/CoFe 25 Å/Cu 22 Å/CoFe 20 Å/NiFe 40 Å/Ta 40 Å) show Hex=855 Oe (Jex=0.3 erg/cm2) and magnetoresistance (MR)=7.1%. The incorporation of nano-oxide layers in spin valves increases the MR signal to 11%. No signal degradation is found in these specular structures for anneals up to 310 °C. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1354581
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  • 10
    Electronic Resource
    Electronic Resource
    Buried word line planarization and roughness control for tunnel junction magnetic random access memory switching (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 6382-6384 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Spin dependent tunnel junctions were fabricated on top of buried word lines. This was achieved modifying an existent 1.2 μm complementary metal–oxide–semiconductor backend metalization process. The word lines are 0.2 μm thick and 4 μm wide. Roughness over the buried line was decreased to 0.2 nm (rms), performing a spin-on-glass local planarization step. Tunnel junctions with 9–13 Å plasma oxidized Al barriers were patterned on top of the word line with different aspect ratios from 3×2 μm2 to 7×1 μm2 areas. Magnetoresistance values reach over 20% for top free electrode configurations. In this inverted structure the magnetization of the free electrode can be fully reversed with the field from word line. The word line creates a field of 0.7 Oe per mA. Applying simultaneously two perpendicular fields reduces the threshold for magnetization switching. The fabricated structure can be used to assess the junction switching mechanism for tunnel junction magnetic random access memories. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372713
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