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1 May 2007

Volume 101, Issue 9, Articles (09xxxx)

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back to top Spin Dependent Properties and Spin Manipulation for Spintronics

High magnetic field properties of yttrium-substituted Ho6Fe23 alloys and deuterides

J. Ostoréro and M. Guillot

J. Appl. Phys. 101, 09B101 (2007); http://dx.doi.org/10.1063/1.2694020 (3 pages) | Cited 1 time

Online Publication Date: 23 March 2007

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The magnetic properties of the Ho6−xYxFe23Dz (x = 0, 0.5, 1 and z = 0, 16) deuterides and of the parent alloys are studied under high dc magnetic field (230 kOe) on samples oriented parallel and perpendicular to the external field in the 4.2–300 K temperature range. All compounds that retain the cubic Fm3m crystallographic structure present canted ferrimagnetic structure. For most of the samples, field-induced transitions characterized by a linear variation of M above the transition field are found. Upon deuteration drastic changes of the magnetic properties are observed and the main “magnetic parameters” are then determined. In the alloys the exchange interaction Ho–Fe increases when the yttrium content increases but decreases in the deuterides. For all alloys the Curie temperature remains close to 510 K.
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75.50.Gg Ferrimagnetics
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.30.Et Exchange and superexchange interactions
71.70.Gm Exchange interactions
61.66.Dk Alloys
61.66.Fn Inorganic compounds

Resonant magnetoresistance in organic spin valves (invited)

A. Reily Rocha and S. Sanvito

J. Appl. Phys. 101, 09B102 (2007); http://dx.doi.org/10.1063/1.2710212 (5 pages) | Cited 9 times

Online Publication Date: 20 April 2007

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We investigate theoretically the effects of surface states over the magnetoresistance of Ni-based organic spin valves. In particular, we perform ab initio electronic transport calculations for a benzene-thiolate molecule chemically attached to a Ni [001] surface and contacted either by Te to another Ni [001] surface or terminated by a thiol group and probed by a Ni scanning tunnel microscope (STM) tip. In the case of S- and Te-bonded molecules we find a large asymmetry in the spin currents as a function of the bias, although the I‐V is rather symmetric. This leads to a smooth although not monotonic dependence of the magnetoresistance over the bias. In contrast, in the case of a STM-type geometry we demonstrate that the spin current and the magnetoresistance can be drastically changed with bias. This is the result of a resonance between a spin-polarized surface state of the substrate and the d-shell band edge of the tip.
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75.47.Pq Other materials
72.20.My Galvanomagnetic and other magnetotransport effects
73.20.At Surface states, band structure, electron density of states
71.15.-m Methods of electronic structure calculations
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)

Electrical detection of spin currents: The spin-current induced Hall effect (invited)

S. O. Valenzuela and M. Tinkham

J. Appl. Phys. 101, 09B103 (2007); http://dx.doi.org/10.1063/1.2710794 (6 pages) | Cited 15 times

Online Publication Date: 26 April 2007

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We demonstrate electrical detection of spin currents in metallic nanostructures. In a conductor with nonzero spin-orbit coupling, a spin current is predicted in a direction perpendicular to the applied electric field, giving rise to a spin Hall effect, where electrons with opposite spin orientations accumulate at opposite edges of the sample. Conversely, when a spin current is present, a charge imbalance is expected, following the Onsager reciprocal relations between spin and charge currents. We report direct electronic measurements of this effect in a lateral geometry by using a ferromagnetic electrode in combination with a tunnel barrier to inject a spin-polarized current in a paramagnetic conductor. We observe a laterally induced voltage in the latter that results from the conversion of the injected spin current into charge imbalance owing to the spin-orbit coupling. Such a voltage is proportional to the component of the injected spins that is perpendicular to the plane defined by the spin-current direction and the voltage probes. By using this technique in CoFe–Al2O3–Al devices, we determine the spin Hall conductivity of aluminum.
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73.63.-b Electronic transport in nanoscale materials and structures
73.40.Rw Metal-insulator-metal structures
72.25.Mk Spin transport through interfaces
72.25.Hg Electrical injection of spin polarized carriers
72.15.Gd Galvanomagnetic and other magnetotransport effects
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect

Role of thermodynamic fluctuations in magnetic recording (invited)

Ralph Skomski

J. Appl. Phys. 101, 09B104 (2007); http://dx.doi.org/10.1063/1.2714322 (6 pages) | Cited 6 times

Online Publication Date: 8 May 2007

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The thermal stability of the information stored in magnetic recording media is determined by a complex hierarchy. The leading consideration is the static or zero-temperature magnetization reversal complemented by the intrinsic temperature dependence of the micromagnetic parameters. Thermally activated Arrhenius (or Néel-Brown) processes modify the reversal by realizing paths close to static reversal, whereas “giant fluctuations” corresponding to reversal fields much higher than the nucleation field can safely be excluded. Thermally activated reversal in very thin elongated nanoparticles limits the thermal stability of magnetic recording media but degenerates into coherent rotation as the temperature is lowered, thereby reconciling micromagnetism and thermodynamics. A particularly complicated situation is encountered in alloys, where sublattices containing heavy transition-metal atoms act like earthquakes that modify the energy landscape.
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75.50.Ss Magnetic recording materials
75.50.Tt Fine-particle systems; nanocrystalline materials
65.80.-g Thermal properties of small particles, nanocrystals, nanotubes, and other related systems
75.60.Jk Magnetization reversal mechanisms
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