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9 Apr 2001

Volume 78, Issue 15, pp. 2095-2255

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Effects of oxide seed and cap layers on magnetic properties of a synthetic spin valve

Tsann Lin and Daniele Mauri

Appl. Phys. Lett. 78, 2181 (2001); http://dx.doi.org/10.1063/1.1361103 (3 pages) | Cited 14 times

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A synthetic spin valve comprising Al2O3/Ni–Cr–Fe/Ni–Fe/Pt–Mn/Co–Fe/Ru/Co–Fe/Cu/Co–Fe/Ni–Fe/Cu/Al2O3/Ta films has been annealed and evaluated as a read sensor for ultrahigh-density ( ≥ 20 Gb/in.2) recording. The Al2O3 film used as its oxide seed layer provides an in situ flat surface for the Pt–Mn, Co–Fe and Ni–Fe films to develop strong {111} crystalline textures, thereby increasing its giant magnetoresistance coefficient to as high as 13.8%. Another Al2O3 film used as its oxide cap layer protects the Co–Fe/Ni–Fe sense layers from interface mixing and oxygen interdiffusion, thus improving the soft magnetic properties and thermal stability of the sense layers. Antiferromagnetic/ferromagnetic coupling between the Pt–Mn pinning and Co–Fe/Ru/Co–Fe synthetic pinned layers is strong and thermally stable enough for proper sensor operation. Ferromagnetic/ferromagnetic coupling across the Cu spacer layer is antiparallel, and hence it is feasible to achieve optimal biasing of magnetoresistance responses. This synthetic spin valve is sandwiched into a read gap 0.1 μm in thickness, and is patterned and lapped into a read sensor 0.42 and 0.23 μm in physical width and height, respectively. With a sense current of 4 mA, this read sensor exhibits an effective read width of 0.31 μm, stable magnetoresistance responses, and signal sensitivity of 6.64 mV/μm. © 2001 American Institute of Physics.
Show PACS
85.75.Bb Magnetic memory using giant magnetoresistance
75.47.De Giant magnetoresistance
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.50.Bb Fe and its alloys
75.30.Et Exchange and superexchange interactions
75.50.Ee Antiferromagnetics

Spin filtering in a magnetic–electric barrier structure

G. Papp and F. M. Peeters

Appl. Phys. Lett. 78, 2184 (2001); http://dx.doi.org/10.1063/1.1360224 (3 pages) | Cited 102 times

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The spin-dependent tunnelling of two-dimensional electrons through a magnetic barrier can be substantially enhanced by the addition of an electric barrier. The spin polarization is found to be strongly dependent on the incident wave vector parallel to the barrier, the incident electron energy, and the height of the electric barrier. The conductance for the spin-up and spin-down electrons can be tuned with this electrical barrier. © 2001 American Institute of Physics.
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75.45.+j Macroscopic quantum phenomena in magnetic systems
72.25.Mk Spin transport through interfaces
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
73.40.Gk Tunneling
73.23.Hk Coulomb blockade; single-electron tunneling

Synthesis, self-assembly, and magnetic behavior of a two-dimensional superlattice of single-crystal ε-Co nanoparticles

Victor F. Puntes, Kannan M. Krishnan, and Paul Alivisatos

Appl. Phys. Lett. 78, 2187 (2001); http://dx.doi.org/10.1063/1.1362333 (3 pages) | Cited 132 times

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A method of producing high-quality magnetic colloidal dispersions by the rapid pyrolysis of cobalt carbonyl in an inert atmosphere was employed to produce monodispersed, stabilized, defect-free ε-cobalt nanocrystals, with spherical shapes and sizes ranging from 3 to 17 nm. The size distribution and the shape of the nanocrystals were controlled by varying the surfactant (oleic acid, phosphonic oxides and acids, etc.), its concentration, and the reaction temperature. These particles have been observed to produce two-dimensional self-assemblies when evaporated at low rates in a controlled atmosphere. A collective behavior due to dipolar interactions has been observed in the low susceptibility measurements corresponding to a highly ordered fine particles system. © 2001 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
81.16.Be Chemical synthesis methods
81.16.Dn Self-assembly
75.50.Tt Fine-particle systems; nanocrystalline materials
81.05.Cy Elemental semiconductors
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
81.07.Wx Nanopowders
81.05.Bx Metals, semimetals, and alloys
75.50.Mm Magnetic liquids
68.65.Cd Superlattices
81.07.Bc Nanocrystalline materials

Magnetic recording medium with improved temporal stability

P. J. Jensen

Appl. Phys. Lett. 78, 2190 (2001); http://dx.doi.org/10.1063/1.1362282 (3 pages) | Cited 10 times

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The current effort to fabricate nonvolatile magnetic recording media with a high areal density is deteriorated by the increasing temporal instability of the stored information. If the stored energy per magnetic particle competes with the thermal energy, spontaneous magnetic reversal processes may occur. Deposition of the magnetic particles on top of an antiferromagnetic substrate will increase its energy barrier due to the exchange coupling between the two subsystems. For this, the magnetic moments of the antiferromagnet in the vicinity of the magnetic particle have to deviate from their undisturbed arrangement. This disturbance vanishes within a few lattice constants. In the framework of a classical spin model, we calculate the spin arrangements and the resulting energy barriers for typical systems. © 2001 American Institute of Physics.
Show PACS
75.50.Ss Magnetic recording materials
75.50.Tt Fine-particle systems; nanocrystalline materials
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
75.10.Hk Classical spin models
75.30.Et Exchange and superexchange interactions
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
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