Abstract
Ferromagnets are commonly magnetized by either external magnetic fields or spin polarized currents. The manipulation of magnetization by spin-current occurs through the spin-transfer-torque effect, which is applied, for example, in modern magnetoresistive random access memory. However, the current density required for the spin-transfer torque is of the order of 1 × 106 A·cm−2, or about 1 × 1025 electrons s−1 cm−2. This relatively high current density significantly affects the devices’ structure and performance. Here we demonstrate magnetization switching of ferromagnetic thin layers that is induced solely by adsorption of chiral molecules. In this case, about 1013 electrons per cm2 are sufficient to induce magnetization reversal. The direction of the magnetization depends on the handedness of the adsorbed chiral molecules. Local magnetization switching is achieved by adsorbing a chiral self-assembled molecular monolayer on a gold-coated ferromagnetic layer with perpendicular magnetic anisotropy. These results present a simple low-power magnetization mechanism when operating at ambient conditions.
Highlights
Ferromagnets are commonly magnetized by either external magnetic fields or spin polarized currents
Two main problems restrict the use of the spin-transfer torque (STT) effect in operating devices: First, the STT usually requires the use of complicated materials and systems, and second, the STT effect efficiency is low
The charge transfer induced by the self-assembled monolayer (SAM) formation is responsible for the interesting room temperature (RT) magnetic properties observed when thiolated molecules are adsorbed onto gold[2,11,12]
Summary
Ferromagnets are commonly magnetized by either external magnetic fields or spin polarized currents. Local magnetization switching is achieved by adsorbing a chiral self-assembled molecular monolayer on a gold-coated ferromagnetic layer with perpendicular magnetic anisotropy. As a result of the CISS effect, spin-polarized electron current is produced that can be used to magnetize ferromagnets This concept was demonstrated in optical[15] and electrical[16] based devices by driving electrons through chiral layers. In this work we combined the two properties, the SAM adsorption-induced charge transfer and the CISS effect, to demonstrate the ability to magnetize a FM layer by adsorption of a SAM made from chiral molecules These results demonstrate magnetization switching of FM thin layers, which is induced solely by adsorption of chiral molecules (magnetism induced by proximity of adsorbed chiral molecules), where less than 1013 electrons per cm[2] are sufficient to induce the magnetization reversal on a gold-coated thin FM layer with perpendicular magnetic anisotropy. The direction of the magnetization depends on the handedness of the adsorbed chiral molecules
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