[21p-W241-1~21] 10.2 Spin torque, spin current, circuits, and measurement technologies

▲ [21p-W241-19] Mag-flip spin torque oscillator using highly spin polarized Heusler alloy as spin injection layer for microwave assisted magnetic recording

〇(PC)Subrojati Bosu¹, Hossein Sepehri-Amin¹, Yuya Sakuraba¹, Shinya Kasai¹, Masamitsu Hayashi¹, Kazuhiro Hono¹ (1.National Institute for Materials Science, Tsukuba, Japan)

Keywords:Microwave assisted magnetic recording (MAMR),mag-flip spin torque oscillator,Heusler alloy

A major challenge for practical use of microwave assisted magnetic recording (MAMR) for next generation high areal density magnetic recording is the development of a mag-flip spin torque oscillator (STO)[1] consisting of the in-plane magnetized field generating layer (FGL) and the perpendicular magnetized spin-injection layer (SIL) that is able to generate a large H_ac from FGL with a frequency over 20 GHz at small bias current density J_C < 1.0 × 10¹² A/m² [2]. Solid understanding of underlying mechanism of the large angle out-of-plane precession (OPP) is equally essential. Very recently, we reported [3] reduction of J_C about 50% by using highly spin polarized Heusler alloy Co₂FeGaGe (CFGG)/FePt SIL compared to a reference Fe₂Co/FePt SIL for spin torque induced oscillation with frequency f ~ 15 GHz in STOs with CFGG FGL. In the present study, we have investigated the oscillation behavior in a 40 nm diameter circular pillar mag-flip STO device using Fe₂Co FGL layer with saturation magnetization µ₀M_s ~ 2.3 T in order to acquire high H_ac, since H_ac is proportional to the magnetization volume of FGL. A large angle OPP mode with a maximum f~21 GHz have been observed for |I_dc |= 6 mA at an external magnetic field µ₀H_ext~1.09 T.
References: [1] J. Zhu et al., IEEE Trans. Magn. 44, 125 (2008), [2] A. Takeo et al., Intermag Conference 2014 (AD-02), [3] Bosu et al., (submitted)