ABSTRACT
Not only since the progressive reduction of structure sizes in modern micro- and nanotechnology, surface and interface effects have played an ever-increasing role and nowadays often dominate the behavior of entire systems. Therefore, understanding the nature of surface and interface effects and being able to fully control them is of fundamental importance, in particular in modern thin-film technology. In this study, it is revealed how Co/Pt multilayer-based synthetic antiferromagnets (SAFs) with perpendicular magnetic anisotropy in the regime of dominating antiferromagnetic interlayer exchange can be employed to control the collective magnetic reversal via systematically altering surface and interface effects. The specifically designed samples and experiments highlight the superior tunability of synthetic systems as compared to their intrinsic stoichiometric counterparts, where the antiferromagnetism is directly tied to the indivisible discrete atomic nature and crystal structure of the materials. Thus, it is demonstrated that in SAFs, it becomes possible to energetically heal the broken magnetic symmetry at the surface, thereby enabling either on demand suppression or controlled enhancement of respective surface and interface effects, as demonstrated here in this study for the surface spin-flop and the exchange bias effect.
ABSTRACT
Wearable sensors are gaining attention in human health monitoring applications, even if their usability is limited due to battery need. Flexible nanogenerators (NGs) converting biomechanical energy into electrical energy offer an interesting solution, as they can supply the sensors or extend the battery lifetime. Herein, flexible generators based on lead-free barium titanate (BaTiO3) and a polydimethylsiloxane (PDMS) polymer have been developed. A comparative study was performed to investigate the impact of multiwalled carbon nanotubes (MWCNTs) via structural, morphological, electrical, and electromechanical measurements. This study demonstrated that MWCNTs boosts the performance of the NG at the percolation threshold. This enhancement is attributed to the enhanced conductivity that promotes charge transfer and enhanced mechanical property and piezoceramics particles distribution. The nanogenerator delivers a maximum open-circuit voltage (VOC) up to 1.5 V and output power of 40 nW, which is two times higher than NG without MWCNTs. Additionally, the performance can be tuned by controlling the composite thickness and the applied frequency. Thicker NG shows a better performance, which enlarges their potential use for harvesting biomechanical energy efficiently up to 11.22 V under palm striking. The voltage output dependency on temperature was also investigated. The results show that the output voltage changes enormously with the temperature.
Subject(s)
Nanotubes, Carbon , Polymers , Barium Compounds , Dimethylpolysiloxanes , Electric Power Supplies , Humans , TitaniumABSTRACT
Ultrafast demagnetization in diverse materials has sparked immense research activities due to its captivating richness and contested underlying mechanisms. Among these, the two most celebrated mechanisms have been the spin-flip scattering (SFS) and spin transport (ST) of optically excited carriers. In this work, we have investigated femtosecond laser-induced ultrafast demagnetization in perpendicular magnetic anisotropy-based synthetic antiferromagnets (p-SAFs) where [Co/Pt]n-1/Co multilayer blocks are separated by Ru or Ir spacers. Our investigation conclusively shows that the ST of optically excited carriers can have a significant contribution to the ultrafast demagnetization in addition to SFS processes. Moreover, we have also achieved an active control over the individual mechanisms by specially designing the SAF samples and altering the external magnetic field and excitation fluence. Our study provides a vital understanding of the underlying mechanism of ultrafast demagnetization in synthetic antiferromagnets, which will be crucial in future research and applications of antiferromagnetic spintronics.