Microwave-magnetic-field-induced magnetization excitation and assisted switching of antiferromagnetically coupled magnetic bilayer with perpendicular magnetization

Abstract

Antiferromagnetically coupled (AFC) magnetic bilayer is a candidate media structure for high-density magnetic recording. Because the stray fields from the two magnetic layers of the AFC bilayer cancel each other out, switching field distribution originating from the stray fields from the adjacent data bits can be suppressed. Furthermore, in microwave-assisted magnetic recording (MAMR), which utilizes ferromagnetic resonance (FMR) excitation in a microwave field to reverse a high-anisotropy magnetic material, AFC media can suppress the distribution in FMR frequency originating from the stray fields and improve MAMR performance. In this study, we fabricate an AFC magnetic bilayer consisting of two Co/Pt multilayers with perpendicular magnetization. We use anomalous-Hall-effect-FMR in combination with a circularly polarized microwave field and carry out layer-selective analysis of FMR excitation of the two magnetic layers. We then investigate the switching behavior of an AFC bilayer nanodot in a microwave magnetic field. The switching field decreases with increasing microwave field frequency and increases abruptly at the critical frequency, and a large switching field reduction by applying a microwave field is demonstrated. This switching behavior is similar to that of a single-layer perpendicular magnetic nanodot, showing that the AFC structure does not hinder the microwave assist effect.