The Speaker: Alexander Goncharov

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A. V. GONCHAROV¹, A. BASHIR² and P. VAN DER HEIJDEN³

1) Western Digital Corporation, San Jose, USA, alexander.goncharov@wdc.com

2) Western Digital Corporation, San Jose, USA, asif.bashir@wdc.com

3) Western Digital Corporation, San Jose, USA, paul.vanderhejden@wdc.com

Abstract

Microwave Assisted Magnetic Recording (MAMR) is one of the key technologies with a potential for increasing recording densities up to 3 Tb/in² [1]. A typical source of microwave AC field in the media is a Spin Torque Oscillator (STO), positioned in the gap between the main pole and trailing shield of the recording head [1], [2]. Basic STO design consists of two magnetic layers separated by a metallic non-magnetic spacer. In this work, a system of differential equations describing stability of a spin torque oscillator (STO) with two free layers is introduced. The system is derived from the Landau-Lifshitz-Gilbert (LLG) equation for two freely rotating magnetic moments interacting via spin torque. In the case of two free magnetic layers, the magnetization of each layer can precess at its own frequency, which is directly proportional to the local effective field in the layer. The spin torque depends on the relative angle between two layers. Therefore, if the magnetization in two magnetic layers rotate with different frequencies, the spin torque will vary in time. This can lead to instabilities of the precession angle in both layers. When two layers oscillate at equal frequencies, instabilities due to spin torque variations are eliminated. Requirement for the synchronization leads to a system of three differential equations for three unknowns. Stable oscillation orbits for each layer are obtained by finding fixed point solutions of the system. Results were confirmed using FEM micromagnetic simulations.

Speaker’s Short Bio:

Alexander Goncharov is a Technologist at Western Digital, where he has contributed to R&D efforts for ten years. He earned his MSc in Physics at Lomonosov Moscow State University, and his PhD (also in Physics) at the University of Southampton in the UK.  A post-doctoral researcher position at the University of Sheffield marked Alexander’s last period in an academic setting prior to being hired by HGST in 2010.  He authored and co-authored numerous scholarly articles and patents, where his insight into the dynamics of magnetization have allowed him to provide valuable contributions to the physics of magnetic recording heads. He developed a high performance numerical micromagnetic software, TGMag, for multi-scale micromagnetic simulations currently used in the design of advanced magnetic recording heads at Western Digital. His research interests include computational physics, micromagnetics, magnetic recording and memory technologies.

REFERENCES

• Jian-Gang Zhu, Xiaochun Zhu, Yuhui Tang, Microwave Assisted Magnetic Recording, IEEE Trans. Magn., 44(1), 2008, pp. 125-131
• Igarashi, Y. Suzuki, H. Miyamoto, Y. Maruyama and Y. Shiroishi, Effect of Elliptical High-Frequency Field on Microwave-Assisted Magnetic Switching, IEEE Trans. Magn., vol. 45(10), 2009, pp. 3711-3713