Quantum 1/f noise in spintronics and the future of downscaling

Abstract

Spintronics is a new direction in electronics. It contains many applications, including spin valves, GMR devices, "spin batteries," spin-controlled electronic devices, and even spin -controlled wide-bandgap compound semiconductors due to the development of rare-earth-doped nitrides with ferromagnetic properties. Spintronics allows for manipulation of both the spin transport and the charge transported by the electrons. It allows the downscaling to lower device sizes and extension of Moore's law to higher device densities, because it requires less energy to just control the spin of the electron, and the quantum 1/f noise associated with spin control is several orders of magnitude below that associated with conventional electronics. However, the injected spin-polarized current is subject to spin-flip due to various causes. The rate of each of these spin-flip currents is affected by quantum 1/f noise, because of the low-frequency photon emission amplitude that is associated with the elementary spin flip process, no matter what causes the spin flip. As a result, in a spin valve, the leakage current will show 1/f noise. In devices with injection and subsequent control of spin-polarized electrons, the effects obtained will also show this spintronic quantum 1/f noise. For instance, the light output of a spin-controlled LED will exhibit quantum 1/f intensity fluctuations. The present paper calculates the 1/f noise expected in spintronic currents. The spectral density of this fundamental 1/f noise is inherently proportional to the square of the current that is affected by it, but is also inversely proportional to the number of carriers defining this current. The latter dependence can cause the spectrum to be proportional to the first power of the current.