[17p-Z19-1~7] 10.2 Fundamental and exploratory device technologies for spin

▲ [17p-Z19-3] A new characterization method for spin-torque oscillator (STO) using injection locking

〇(PC)Nagarjuna Asam¹, Hirofumi Suto², Shingo Tamaru³, Hossein Sepehri-Amin¹, Tomoya Nakatani¹, Weinan Zhou¹, Hitoshi Kubota³, Yuya Sakuraba¹ (1.NIMS, 2.Toshiba Corp., 3.AIST)

Keywords:Magnetization dynamics, Injection locking, MAMR

Spin-torque oscillator(STO) is a spintronic device that generates radio-frequency (RF) oscillating magnetic field for Microwave-Assisted magnetic recording (MAMR) application. This STO is usually placed between the write pole and trailing shield of the recording head, but RF signal is heavily attenuated by connecting STO directly to a radio-frequency (RF) characterization device such as spectrum analyzer via the write-head assembly, making it difficult to inspect the frequency of the oscillating magnetic field. Therefore, we are proposing a new experimental method to characterize the oscillation frequency of spin-torque oscillator using injection locking from externally RF magnetic field, which can be utilized without connecting an RF-compatible electric circuit with the STO. When an STO is under oscillation, it can undergo injection locking to an externally applied oscillating magnetic field whose frequency is close to the original oscillation frequency. This changes the trajectory of magnetization oscillation and hence the dc resistance. If we can detect the change of dc resistance of the STO as an indicator of injection locking, we can identify the frequency at which injection locking occurs, which represents the actual oscillation frequency of the STO. Thus, we can characterize the oscillation frequency of the STO. Using this method, there is no need to electrically connect the STO to a spectrum analyzer via an RF-compatible electrical circuit, thus beneficial for inspecting a magnetization oscillation in the product-level STO for MAMR assembled with a write-head.