[21p-E216-1~6] 10.3 Spin devices, magnetic memories and storages

▼ [21p-E216-6] Magnoise and 1/f noise of magnetic vortex states in magnetic tunnel junctions

〇Ryota Okuno¹, Minori Goto^1,2, Sumito Tsunegi³, Kay Yakushiji³, Hitoshi Kubota³, Akio Fukushima³, Shinji Yuasa³, Hikaru Nomura^1,2, Yoshishige Suzuki^1,2,3 (1.Osaka Univ., 2.CSRN Osaka, 3.AIST)

Keywords:magnetic tunnel junction, magnetic vortex, sensor

The knowledge of magnetic noise in devices is important for realizing highly sensitive magnetic field sensors. In these several decades, magnetic noise such as magnoise, nonlinear magnoise, and 1/f noise has been reported in magnetic tunnel junctions (MTJs) with single domain states. Moreover, the low frequency noise has been studied in a MTJ with the magnetic vortex state which is the candidate for a highly sensitive sensor with wide dynamic range because of its negligible hysteresis and high saturation field. However, the magnetic noise of the magnetic vortex state is not studied in wide frequency range. In particular, 1/f noise mainly limits the sensitivity of sensors, therefore, to clarify the mechanism of the magnetic 1/f noise in the magnetic vortex is an important subject. In this study, we investigate the magnetic noise in the MTJ with a magnetic vortex state in the free layer (FL).
The film structure is Buffer/ IrMn(6)/ CoFe(2.5)/ Ru(0.85)/ CoFeB(2.1) and CoFe(0.4) pinned layer/ MgO(1.1)/ FeB(5) magnetic vortex FL/ MgO(1.1)/ Ta(5)/ Ru(5) (nm in thickness). The magnetic vortex structure forms in the zero magnetic field and the magnoise peak appears in the MHz frequency range. The peak intensity of magnoise is proportional to the square of the voltage. This result is consistent to the behavior of the power spectrum induced by thermal fluctuation of a vortex-core. Furthermore, 1/f magnetic noise of the magnetic vortex is observed in the MHz frequency range. Our results provide the fundamental knowledge to discuss feasibility of the magnetic field sensor using the magnetic vortex.
This research was supported by Bilateral Programs (MEXT) and JSPS KAKENHI (Grant No. JP16H03850).