R&D: Antiferromagnetically Coupled Media for MAMR

IEEE Transactions on Magnetics (Volume: 54, Issue: 2, Feb. 2018 ) has published an article written by Simon Greaves, RIEC, Tohoku University, Sendai, Japan, Yasushi Kanai, Department of Information and Electronics Engineering, Niigata Institute of Technology, Kashiwazaki, Japan, and Hiroaki Muraoka, RIEC, Tohoku University, Sendai, Japan

Introduction: “Microwave-assisted magnetic recording (MAMR) technology can increase the effective head field gradient and reduce the switching field of a recording medium [1]; it may also allow selective recording on multiple-layer media [2], [3]. In an MAMR system, a high-frequency (HF) field is generated by a spin-torque oscillator (STO). One issue is the dependence of the optimum HF field frequency on the magnetic state of the medium, e.g., the optimum HF field frequency may differ depending on whether the medium is ac-demagnetized or saturated [4]. This behavior originates from magnetostatic field interactions between media grains. In the past, antiferromagnetically coupled (AFC) media have been used to reduce magnetostatic interactions in longitudinal media [5], and a similar approach can be used in perpendicular media [6]. In this paper, we investigate AFC media for MAMR, compare them with single-layer (SL) media, and examine the prospects for a multiple-layer recording system.“