Influence of interface exchange coupling in perpendicular anisotropy[Pt/Co]50/TbFebilayers

Abstract

We present the magnetization evolution of perpendicular anisotropy TbFe and ͓Co/ Pt͔ 50 thin films either in direct contact resulting in antiferromagnetic interfacial coupling or separated by a thick decoupling Pt layer. Magnetometry and x-ray magnetic circular dichroism spectroscopy determine the spatially averaged magnetic properties. Resonant magnetic x-ray small-angle scattering and magnetic soft x-ray transmission microscopy probed the domain configurations and correlations in the reversal processes. While the Co/Pt multilayer reverses by domain propagation, the TbFe magnetization reversal was dominated either by coherent magnetization reversal processes or by lateral domain formation depending on the interface exchange coupling. In the presence of lateral domains, dipolar field induced domain replication phenomena were observed.

Double exchange bias in ferrimagnetic heterostructures

“…With increasing temperature, the EB shift gets slightly reduced and starts to vanish above 140 K, as indicated by the appearance of a symmetric reversal part of the hysteresis between ±15 kOe, which becomes more pronounced with increasing temperature. At 200 K and above, a fully symmetric hysteresis loop, characteristic of an antiferromagnetically coupled bilayer, as discussed before, is observed [11,14]. By cooling the system down to 80 K in a negative field of −70 kOe and measuring subsequently hysteresis loops from 80 K toward higher temperatures, the same evolution of the EB phenomenon is observed, except that the shifts are inverted [ Fig.…”

“…In addition to AFM/FM interfaces, EB has also been reported in systems with ferrimagnetic (FI)/FM layers [10][11][12][13][14][15][16][17][18][19][20][21][22][23], resulting in giant EB fields in the order of several tens of kilo-Oersteds [13,14,[24][25][26]. In particular, FI layers consisting of amorphous heavy rare earth (RE)-3d transition metal (TM) alloys provide further benefits as a pinning layer since these alloys can exhibit large interfacial exchange interaction and zero moment at the compensation temperature T comp .…”

“…Considering a heterostructure, consisting of two FI layers, where one layer is RE dominated and the other is TM dominated, in the ground state, the net moments of each layer are antiparallel aligned. However, by reversing the softer layer against the hard layer, an interfacial domain wall (IDW) at the transition region between the two layers will be created [11,14]. Reducing the external field leads to annihilation of the IDW, forcing the softer layer to rotate back which results in a positive loop shift under this minor loop condition.…”

Exploring nanoscale magnetism in advanced materials with polarized X-rays

“…As a prototype system we want to show results from a bilayer structure consisting of a perpendicular anisotropy [Pt/Co] 50 multilayer and a TbFe ferromagnetic alloy [130]. Fig.…”

Phase diagram in exchange-coupled CoTb/[Co/Pt] multilayer-based magnetic tunnel junctions

“…Magnetic multilayers made of two directly interacting ferromagnetic layers have been at the center of many theoretical and experimental studies [1], by the use of different materials, different magnetic geometries (in plane [2] and out-of-plane [3]), and different experimental technics [4][5][6][7]. The main objectives are the development of new functionalities [8,9] and new materials for a wide variety of potential applications: nanoscale composites for hard magnets [10], exchangecoupled composite structures to reduce the switching field amplitude in storage media [11], exchange-coupled multilayers to stabilize hard reference layers in the well-known spin valve structures [12], and future applications in spin-transfer torquebased devices [13].…”