Layer-Selective Switching of a Double-Layer Perpendicular Magnetic Nanodot Using Microwave Assistance

Abstract

Layer-selective manipulation of magnetization direction in a multilayer magnetic structure offers a way to develop a large-capacity magnetic recording device with multiple recording layers. Here, we use a double-layer perpendicular magnetic nanodot consisting of two layers with low and high perpendicular magnetic anisotropy (PMA) and show that layer-selective magnetization switching can be accomplished by utilizing a microwave-assisted magnetization switching technique. Since the low-and high-PMA magnetic layers have different ferromagnetic resonance (FMR) frequencies, their magnetization excitation that reduces the switching field can be individually induced by adjusting the frequency of the applied microwave field (rf), and this principle allows rf to select the layer to be switched. In addition, by measuring thermally excited FMR signals from the nanodot, we find that the magnetization dynamics of the two PMA layers couple through interactions, and we identify the excitation modes responsible for the layer-selective magnetization switching.

Domain-Wall Motion Driven by Laplace Pressure in Co−Fe−B/MgO Nanodots with Perpendicular Anisotropy

“…This leads to a dispersion of the magnetic properties, which strongly affects the switching mechanism when the dimension of the nanostructures becomes smaller. In particular, this has been extensively shown for the switching process of magnetic dots [13,14,15,16,17,18]. When the size of the dots is sufficiently large, the dominant mechanism for switching has been found to be nucleation followed by rapid propagation of magnetic domain walls (DWs).…”

An analytical computation of magnetic field generated from a cylinder ferromagnet

“…It was also shown that the magnetization dynamics, such as switching and auto-oscillation, can be excited by spin transfer effect [18] in nanostructured ferromagnetic multilayers [19]. In these dynamic states, several ferromagnets located close to each other within a nanoscale distance affect each other and show a coupled motion of the magnetizations, such as a resonant switching and synchronized oscillation, through stray (dipole) fields from each ferromagnet [20,21,22,23,24,25,26,27,28,29,30,31,32]. Such magnetization dynamics and/or cooperative phenomena are useful for practical applications such as high-density magnetic recording, microwave generators, and neuromorphic architectures.…”

Zero-dc-field rotation-direction-dependent magnetization switching induced by a circularly polarized microwave magnetic field

“…Furthermore, the use of FMR excitation can provide novel techniques for manipulating magnetization direction. One is layer-selective MAS, which has been explored as a writing method for multilayer recording 7 , 8 . When a multilayer magnetic structure with each layer having a different FMR frequency is used, switching of only a target layer can be selectively induced by tuning the frequency of the microwave field.…”