Diffusive and ballistic current spin polarization in magnetron-sputtered L10-ordered epitaxial FePt

Seemann, K. M., Baltz, V., MacKenzie, M., Chapman, J. N., Hickey, B. J. and Marrows, C. H. (2007) Diffusive and ballistic current spin polarization in magnetron-sputtered L10-ordered epitaxial FePt. Physical Review B, 76(17), p. 174435. (doi:10.1103/PhysRevB.76.174435)

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Publisher's URL: http://dx.doi.org/10.1103/PhysRevB.76.174435

Abstract

We report on the structural, magnetic, and electron transport properties of an L10-ordered epitaxial iron-platinum alloy layer fabricated by magnetron sputtering on a MgO (001) substrate. The film studied displayed a long-range chemical order parameter of S~0.90, and hence has a very strong perpendicular magnetic anisotropy. In the diffusive electron transport regime, for temperatures ranging from 2 to 258 K, we found hysteresis in the magnetoresistance mainly due to electron scattering from magnetic domain walls. At 2 K, we observed an overall domain wall magnetoresistance of about 0.5%. By evaluating the spin current asymmetry α=σ↑/σ↓, we were able to estimate the diffusive spin current polarization. At all temperatures ranging from 2 to 258 K, we found a diffusive spin current polarization of greater than 80%. To study the ballistic transport regime, we have performed point-contact Andreev-reflection measurements at 4.2 K. We obtained a value for the ballistic current spin polarization of ~42% (which compares very well with that of a polycrystalline thin film of elemental Fe). We attribute the discrepancy to a difference in the characteristic scattering times for oppositely spin-polarized electrons, such scattering times influencing the diffusive but not the ballistic current spin polarization.

Item Type:Articles
Keywords:iron alloys, magnetic anisotropy, magnetic domain walls, magnetic epitaxial layers, magnetic hysteresis, magnetoresistance, metallic epitaxial layers, platinum alloys, point contacts, spin polarised transport, sputter deposition
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:MacKenzie, Dr Maureen and Chapman, Professor John
Authors: Seemann, K. M., Baltz, V., MacKenzie, M., Chapman, J. N., Hickey, B. J., and Marrows, C. H.
Subjects:Q Science > QC Physics
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Physical Review B
Publisher:American Physical Society
ISSN:1098-0121
ISSN (Online):1550-235X

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
402831Spin@RT: Room Temperature SpintronicsJohn ChapmanEngineering & Physical Sciences Research Council (EPSRC)EP/D003199/1Science and Engineering College Senior Management