Nano spin-diodes using FePt-NDs with huge on/off current ratio at room temperature

Abstract

Spin transistors have attracted tremendous interest as new functional devices. However, few studies have investigated enhancements of the ON/OFF current ratio as a function of the electron spin behavior. Here, we found a significantly high spin-dependent current ratio—more than 102 at 1.5 V—when changing the relative direction of the magnetizations between FePt nanodots (NDs) and the CoPtCr-coated atomic force microscope (AFM) probe at room temperature. This means that ON and OFF states were achieved by switching the magnetization of the FePt NDs, which can be regarded as spin-diodes. The FePt magnetic NDs were fabricated by exposing a bi-layer metal stack to a remote H2 plasma (H2-RP) on ~1.7 nm SiO2/Si(100) substrates. The ultrathin bi-layers with a uniform surface coverage are changed drastically to NDs with an areal density as high as ~5 × 1011 cm−2. The FePt NDs exhibit a large perpendicular anisotropy with an out-of-plane coercivity of ~4.8 kOe, reflecting the magneto-crystalline anisotropy of (001) oriented L10 phase FePt. We also designed and fabricated double-stacked FePt-NDs with low and high coercivities sandwiched between an ultra-thin Si-oxide interlayer, and confirmed a high ON/OFF current ratio when switching the relative magnetization directions of the low and high coercivity FePt NDs.

Controlling the spin current around the rectangular cavities in two-dimensional topological insulators

“…8 On the other hand, once the TRS in a TI is broken, 11 for instance by using magnetic defects, 12 ferromagnets, 13,14 or a magnetic field, 15,16 a quantum anomalous Hall effect (QAH) phenomenon can occur, 17 which corresponds to the chiral edge where the spin-up and spin-down modes flow along the same direction on the same upper or lower edges. The breaking of the TRS in 2D TIs can be employed for the creation of nearly perfectly spin-polarized currents, 18 such as highly tunable spin diodes, 19,20 spin valves, 21,22 spin filters, 23–25 and bipolar spin transistors. 26,27 Graphene, 18 silene, 28 and germanium 29 are materials currently being studied as two-dimensional TIs, especially graphene, which has good electron mobility at room temperature.…”

Effect of substrate temperature on plasma-enhanced self-assembling formation of high-density FePt nanodots

“…[25][26][27][28][29] Furthermore, we reported the formation of FePt alloy NDs, which have received attention for the material of high-density magnetic storage devices because its L1 0 -ordered phase has high uniaxial magnetic anisotropy along (001) direction, 30) using by the H 2 -RP exposure without external heating. 31,32) In this work, we extended our research to study the effect of a substrate temperature during the H 2 -RP exposure on the structure and the magnetic properties of NDs.…”