Spatial spin flipping and spin switching phenomena on a Y-shaped graphene nanoribbon ferromagnetic junction with Rashba spin orbit coupling and strain

Abstract

We theoretically study a controllable spatial spin converter and spin valve by using a Y-shaped even-chain zigzag graphene nanoribbon (ZGR) junction with Rashba spin orbit coupling (SOC) and strain. By calculating the spin-dependent conductance spectra of different tunneling terminals through the multi-terminal Landauer formula, we find that the spin up electron can flip its spin orientation, and convert to spin down one on the left electrode, the same spin converting phenomena can be inhibited on the right terminal. The above spin flipping and its valve phenomena are derived from the interactions of the Rashba SOC, strain and magnetization layout. When the strain's orientation is along (perpendicular) to the zigzag chain's direction, the valley valve effect of the even-chain ZGR is remained, the Rashba SOC takes little effect on the spatial spin switching, one can get 100% polarized spin up (down) electrons at different terminals of the Y-shaped ZGR due to the valley valve effect. When the strain is changed to other direction, the valley valve effect is partly destroyed, Rashba SOC can enhance the spin flipping conductance and break the ON/OFF transport states of spin valve. Our investigations might be useful in designing a multi-parameter controllable spin valve and spin detector based on a multi-terminal graphene nanoribbon junction.

Even-odd chain dependent spin valve effect on a zigzag biphenylene nanoribbon junction

“…No spin valve phenomena can be realized (G LRss ′ ̸ = 0) in the whole energy region, that is, all electrons are allowed to transport at [−M, M], thus one cannot obtain and detect 100% polarized spin up (down) electrons when the ZBN has an odd chain's width. The above even-odd chain induced spin valve phenomena in ZBN are very similar to our previous results of zigzag silicene junction under the strain [45]. In [45], we use two uniaxial stresses to realise the spin valve in an evenchain Y-shaped zigzag silicene junction, because the two drain electrodes have the same width, two flipping spin conductances are small and the switching on/off ratios of them are not large under the modulation of Rashba SOC.…”

“…The above even-odd chain induced spin valve phenomena in ZBN are very similar to our previous results of zigzag silicene junction under the strain [45]. In [45], we use two uniaxial stresses to realise the spin valve in an evenchain Y-shaped zigzag silicene junction, because the two drain electrodes have the same width, two flipping spin conductances are small and the switching on/off ratios of them are not large under the modulation of Rashba SOC. In this work, we replaced the even chain zigzag silicene junction by a ZBN junction with different even (odd) chain numbers, and obtain higher-efficient transport for two flipping spin electrons.…”

“…As it is known, it is difficult to devise the electric fieldcontrollable spin filter and spin valve in an odd-chain graphene and silicene junction owing to the valley valve effect [38,39,45]. By calculating the spin-polarization degrees of transmission electrons, we try to reveal gate-controllable spin transport phenomena in different even (odd) chain ZBNs through the Rashba SOC modulation only.…”