Competition between Vortex and “S”-like States in Laterally Confined Magnetic Trilayers

AbstractWe report on the magnetization reversal and micromagnetic configurations of Co(10nm)/Pd(0.8nm)/Co(10nm) and Co (20nm) nanodisks studied as a function of the disk diameter. Using magneto-optical Kerr effect (MOKE) we show that the magnetic fields of vortex nucleation and annihilation decrease while the nanodisk diameter increases. We have discovered that in an array of trilayer nanodisks with diameters D = 200nm, direct exchange through pinholes and interlayer indirect ferromagnetic exchange coupling promote the formation of a non-uniform “S”-like state with opposed magnetic moments in adjacent Co layers. In larger trilayers nanodisks (D = 400 - 800nm) the vortex state, like in single layer nanodisk, is formed

Tuning magnetic interaction between two identical perpendicularly magnetized layers by a nonmagnetic spacer layer

Tuning magnetic properties of perpendicularly magnetized system is technologically important and have application in modern spintronics devices. In this article, we have considered TbFe based perpendicular trilayer magnetic system by inserting a nonmagnetic spacer layer in between. A systematic variation in thickness of non-magnetic Ti spacer (S) in the trilayer structure, TbFe (40 nm)/ Ti (0, 2, 5, 10, 15, 30 nm)/ TbFe (40 nm) is explored to understand and correlate the structural, magnetic, and microscopic properties of the system. Magnetostatic coupling dominates in these systems, and the strength of the coupling decreases as the S thickness increases. Ti and Fe forms a interfacial TiFe layer, roughness of which increases as the thickness of S increases. The increase in interfacial roughness causes effective magnetization compensation at S = 30 nm, where Hc and Mr are least compared to other spacer thicknesses. However, for S = 2 nm coupling strength was found to be highest compared to other cases, as a result, magnetic domains are compressed. Further increase in thickness of S leads to isolated domains and finally a single domain state is apparent for higher value of S. The experimental findings are supported with in-depth micromagnetic modeling. Kerr microscopy and first-order reversal imaging reveal nucleation and domain wall propagation as the dominated magnetization reversal process in these systems. These microscopic insights and tunability of magnetic properties of the trilayer system may find use in various spintronics applications. © 2022 Elsevier B.V