Oscillation Stability of a Small Size Spin Torque Oscillator for MAMR

• Published in: IEEE transactions on magnetics Vol. 49; no. 7; pp. 3628 - 3631
• Main Authors: Watanabe, Katsuro, Sugiura, Kenji, Sato, Yo, Igarashi, Masukazu, Shiroishi, Yoshihiro
• Format: Journal Article Conference Proceeding
• Language: English
• Published: New York, NY IEEE 01.07.2013; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Magnetic recording; Magnetism; Magnetization; Materials science; microwave oscillation; microwave-assisted magnetic recording; Oscillators; Other topics in materials science; Physics; spin torque oscillator; Thermal stability; Torque; Trajectory; Vectors; microwave oscillation; Stability; Microwave radiation; Oscillations; Oscillators; spin torque oscillator; Magnetic recording; Magnetic properties; microwave-assisted magnetic recording
• ISSN: 0018-9464; 1941-0069
• DOI: 10.1109/TMAG.2013.2238222

Oscillation behavior of a spin torque oscillator (STO) less than 40 nm in size was investigated by using micromagnetic simulations for microwave-assisted magnetic recording (MAMR) over 5 Tb/in 2 . Decreasing the STO size from 40 to 20 nm deteriorates the stability of a reference layer (REF) and it shrinks the stable oscillation region of a field generation layer (FGL). Enhancing the magnetic anisotropy energy of the REF K u_REF stabilizes the magnetization motion of the REF against the spin transfer torque (STT) effect and the external magnetic field H z , and the stable oscillation region of the FGL expands within a relative lower applied voltage V sto region, but random oscillation with fluctuating elevation angles appears at a higher H z and V sto . Similar phenomenon is observed when increasing the thickness of the REF t REF . Enhancing both K u_REF × t REF and the thickness of FGL are found to stabilize oscillation of the FGL against the STT effect from a stable REF at a larger strength of H z and a higher V sto without the appearance of random oscillation, making it possible to apply about 20-nm-square STO to a magnetic head for over 5 Tb/in 2 .