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arXiv · 0707.2943

Diffusive and ballistic current spin-polarization in magnetron-sputtered L1o-ordered epitaxial FePt

K. M. Seemann·V. Baltz·M. MacKenzie·J. N. Chapman·B. J. Hickey·C. H. Marrows
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Abstract

We report on the structural, magnetic, and electron transport properties of a L1o-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 K 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 alpha = sigma_up / sigma_down, we were able to estimate the diffusive spin current polarization. At all temperatures ranging from 2 K to 258 K, we found a diffusive spin current polarization of > 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.

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K. M. Seemann, V. Baltz, M. MacKenzie, J. N. Chapman, B. J. Hickey, C. H. Marrows. 2007-07-19. Diffusive and ballistic current spin-polarization in magnetron-sputtered L1o-ordered epitaxial FePt. https://doi.org/10.1103/physrevb.76.174435

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