2016 Fiscal Year Annual Research Report
Intelligent Design of Layered Materials Surface for Spintronics
| Project/Area Number |
16J01006
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| Research Institution | Osaka University |
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Principal Investigator |
ARGUELLES ELVIS FLAVIANO 大阪大学, 工学研究科, 特別研究員(DC2)
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| Project Period (FY) |
2016-04-22 – 2018-03-31
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| Keywords | charge carriers / layered oxide / spintronics |
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| Outline of Annual Research Achievements |
During Heisei 28 financial year, the effects of charge carrier concentration in layered lead oxide (PbO) (001) with magnetic interstitial atom (Fe) and gas molecules-spintronics device interactions have been investigated. It is found that an increase in the hole concentration increases the magnetic moment of the interstitial Fe and PbO surface. This implies that the PbO surface with interstitial Fe may have the ability to preserve the spin polarisation of hole currents, an important characteristic of spin injection spintronics devices.
Further, the effects of gas molecules on the spintronics device have also been investigated by modelling the simplest reaction using H2 adsorption on a representative metal (Pd) surface. This is also essential during the fabrication process wherein industrial gases may intercalate into the layers or adsorb on the surfaces of dilute magnetic oxides or graphene bilayers. It was found that gas molecules strongly change the electronic properties of the metal surface by taking electrons through their antibonding orbitals, leaving holes in the surface. It was also discovered that H2 behaves as a two dimensional (2D) quantum rotor while adsorbed on the surface, eneabling possibilities of separating its nuclear spin isomers. It was also found that gas molecules-PbO with interstitial Fe interaction is mainly governed by weak van der Waals interactions and do not affect the electronic or magnetic property of the surface. This entails that PbO-based spintronic devices are essentially immune to degradation due to interaction with atmospheric gases.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
Currently, the interactions between magnetic atoms and graphene are being investigated. The magnetic moment before and after impurity atoms adsorption on graphene is being evaluated by means of first principles collinear and non-collinear calculation based on the density functional theory (DFT). Upon adsorption, the d or f orbitals with unpaired electrons become delocalised and spin split. These spin splitting induce long range spin polarisation in the host crystal. It is expected that the magnetic exchange mechanism is similar to the layered oxides previously investigated. By changing the chemical potential of graphene, we can effectively see the effects of charge carrier concentration on the magnetic properties of the surface.
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| Strategy for Future Research Activity |
In the future, the formation energies of magnetic atoms introduced in the interstitial sites of bilayer graphene will be investigated by means of first principles calculations based on the density functional theory. Consequently, the induced magnetic moment, exchange mechanism and the magnetic ground state of the system will be evaluated. To estimate up to what temperature the ferromagnetic order is destroyed, the Curie temperature of the system will be investigated by means of non-collinear DFT calculations and mean-field Heisenberg Hamiltonian. A Monte Carlo simulation is also being considered to obtain a more accurate numerical result. Furthermore, it is known that transition metal adsorbates or impurities tend to cluster on one site in the host crystal matrix. These effects will also be considered in the future.
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