The low-frequency and shot noises in spin-valve CoFeB/MgO/CoFeB magnetic tunneling junctions were studied at low temperature. The measured 1/f noise around the magnetic hysteresis loops of the free layer indicates that the main origin of the 1/f noise is the magnetic fluctuation, which is discussed in terms of a fluctuation-dissipation relation. Random telegraph noise (RTN) is observed to be symmetrically enhanced in the hysteresis loop with regard to the two magnetic configurations. We found that this enhancement is caused by the fluctuation between two magnetic states in the free layer. Although the 1/f noise is almost independent of the magnetic configuration, the RTN is enhanced in the antiparallel configuration. These findings indicate the presence of spin-dependent activation of RTN. Shot noise reveals the spin-dependent coherent tunneling process via a crystalline MgO barrier.
@article{arxiv.1301.2161,
title = {Low-frequency and shot noises in CoFeB/MgO/CoFeB magnetic tunneling junctions},
author = {Tomonori Arakawa and Takahiro Tanaka and Kensaku Chida and Sadashige Matsuo and Yoshitaka Nishihara and Daichi Chiba and Kensuke Kobayashi and Teruo Ono and Akio Fukushima and Shinji Yuasa},
journal= {arXiv preprint arXiv:1301.2161},
year = {2013}
}