Abstract:
The discovery of Giant Magnetoresistance (GMR), which won the Nobel Physics Prize in 2007, initiated the study of spintronic materials and spintronic devices. The first generation metallic spintronic devices, such as GMR devices, MTJ devices and MRAM have already been commercialized. The more exciting next generation spintronic devices are semiconductor based spintronic devices, such as spin-FET, spin-LED, spin-RTD, etc. because the spintronic materials cannot only serve as the switch but also a memory cell. Scientists have already successfully injected spin into some semiconducting materials, such as GaAs, to make semiconductor based spintronic material. However, spin injection into Si is only successful at low temperature [1]. Also many attempts have been made to study the C-based spintronic materials. However, until now the carbon nanotubes have magnetoresistance (MR) only at low temperature below 120K [2]
We synthesized (Fe,Co)x-C1-x/Si nanostructures by use of pulsed laser ablation. The (Fe,Co)x-C1-x/Si nanostructures have a room temperature MR of 20-40% at magnetic field of 200-300Oe. The sensitivity of these materials is close to the spin valve structure of GMR material, though our material does not have spin valve structure and it has different mechanism(s) from the all the others known MR mechanisms. (Fe,Co)x-C1-x/Si nanostructure has also bias-dependent MR at low temperature. When bias is 10V the MR of Fe-C/Si heterojunction is 550,000% at 20K and H=5T. Also when H>1.5T, the MR~H curve is almost liner. In addition, the (Fe,Co)x-C1-x nanofilms also show some other novel physical properties, such as giant electroresistance, switch effect, field effect, hysteresis effect on current-voltage curve, photoconductivity and pressure sensitivity Study of (Fe,Co)x-C1-x/Si nanostructures may shed a light on discovery of new spintronic material.
This work has been supported by the key project of The National Science Foundation of China and the preliminary research of 973 project sponsored by Ministry of Science and Technology of China.
References
[1] B.T. Jonker et al, Nature Physics, 3, 542-546, 2007.
[2] L.E. Hueso et al, Nature 445, 410-413, 2007