Abstract
Nanocomposites based on half-metallic FePt (L10) magnetic nanoparticles coated with the semiconducting conjugated polymer poly(3-hexylthiophene-2,5-diyl) (P3HT) show a significant reduction in the magnetic coercivity. This study adopts a physical approach based on chemical potential equalization at the interface. The underlying charge/spin transfer mechanism unveils an imbalance: only spin-down polarized electrons are allowed to be transferred from the semiconductor to the half-metal (spin-down) conduction band, while spin-up states remain blocked at the interface. This process determines an excess of spin-up states on the P3HT side, and due to a RKKY mechanism, this effective spin system becomes ferromagnetic polarized. Due to this proximity effect, the conjugate polymer becomes exchange coupled to the hard magnetic FePt (L10) phase, thus reducing the coercivity of the half-metal. These processes make this type of composite suitable for magnetic recording applications.
Highlights
As a result of various interactions between interfaced materials, the nanoscale composite materials have, besides each component’s specific characteristics, new interesting and synergistic properties.[1–6] Among them, core–shell magnetic nanoparticles with a magnetic core surrounded by shells made from different materials may show modified behaviors with respect to bare core counterparts
Nanocomposites based on half-metallic FePt (L10) magnetic nanoparticles coated with the semiconducting conjugated polymer poly(3hexylthiophene-2,5-diyl) (P3HT) show a significant reduction in the magnetic coercivity
The underlying charge/spin transfer mechanism unveils an imbalance: only spin-down polarized electrons are allowed to be transferred from the semiconductor to the half-metal conduction band, while spin-up states remain blocked at the interface
Summary
As a result of various interactions between interfaced materials, the nanoscale composite materials have, besides each component’s specific characteristics, new interesting and synergistic properties.[1–6] Among them, core–shell magnetic nanoparticles with a magnetic core surrounded by shells made from different materials may show modified behaviors with respect to bare core counterparts. In this specific case, as a possible explanation for the behavior of the hysteresis loops, the reduced size of the magnetic nanoparticles and/or their tendency to form agglomeration were considered as the co-deposited MgO amount increased. We report and discuss the modification of the magnetic behavior of preformed FePt (L10) nanoparticles coated with the semiconductive conjugated polymer poly(3hexylthiophene-2,5-diyl) (P3HT) This is done in correlation with the mentioned modifications of the magnetic saturation magnetization and with the observed hysteresis loop shrinking in the case of FePt (L10) nanocomposites
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