magnetic circular dichroism
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Author(s):  
MICHAEL GUEVARA DE JESUS ◽  
Zhuyun Xiao ◽  
Maite Goiriena-Goikoetxea ◽  
Rajesh V Chopdekar ◽  
Mohanchandra K Panduranga ◽  
...  

Abstract This work demonstrates that magnetoelectric composite heterostructures can be designed at the length scale of 10 microns that can be switched from a magnetized state to a vortex state, effectively switching the magnetization off, using electric field induced strain. This was accomplished using thin film magnetoelectric heterostructures of Fe81.4Ga18.6 on a single crystal (011) [Pb(Mg1/3Nb2/3)O3]0.68-[PbTiO3]0.32 (PMN-32PT) ferroelectric substrate. The heterostructures were tripped from a multi-domain magnetized state to a flux closure vortex state using voltage induced strain in a piezoelectric substrate. FeGa heterostructures were deposited on a Si-substrate for SQUID magnetometry characterization of the magnetic properties. The magnetoelectric coupling of a FeGa continuous film on PMN-32PT was characterized using a MOKE magnetometer with bi-axial strain gauges, and magnetic multi-domain heterostructures were imaged using X-Ray Magnetic Circular Dichroism – Photoemission Electron Microscopy (XMCD-PEEM) during the transition to the vortex state. The domain structures were modelled using MuMax3, a micromagnetics code, and compared with observations. The results provide considerable insight into designing magnetoelectric heterostructures that can be switched from an “on” state to an “off” state using electric field induced strain.


Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 46
Author(s):  
Jannis Thien ◽  
Jascha Bahlmann ◽  
Andreas Alexander ◽  
Kevin Ruwisch ◽  
Jari Rodewald ◽  
...  

Here, we present the (element-specific) magnetic properties and cation ordering for ultrathin Co-rich cobalt ferrite films. Two Co-rich CoxFe3−xO4 films with different stoichiometry (x=1.1 and x=1.4) have been formed by reactive solid phase epitaxy due to post-deposition annealing from epitaxial CoO/Fe3O4 bilayers deposited before on Nb-doped SrTiO3(001). The electronic structure, stoichiometry and homogeneity of the cation distribution of the resulting cobalt ferrite films were verified by angle-resolved hard X-ray photoelectron spectroscopy. From X-ray magnetic circular dichroism measurements, the occupancies of the different sublattices were determined using charge-transfer multiplet calculations. For both ferrite films, a partially inverse spinel structure is found with increased amount of Co3+ cations in the low-spin state on octahedral sites for the Co1.4Fe1.6O4 film. These findings concur with the results obtained by superconducting quantum interference device measurements. Further, the latter measurements revealed the presence of an additional soft magnetic phase probably due to cobalt ferrite islands emerging from the surface, as suggested by atomic force microscope measurements.


2021 ◽  
Author(s):  
Masato Kotsugi ◽  
Tadashi Nishio ◽  
Masahiro Yamamoto ◽  
Takuo Ohkochi ◽  
Daigo Nanasawa ◽  
...  

Abstract Recent progress in materials informatics has triggered growing interest in combinatorial experimental systems for materials development. We demonstrate a novel high-throughput experiment combining compact materials synthesis, synchrotron radiation measurements, and statistical data analysis. This technique focuses on not only drawing phase diagrams but also analysing phase transitions for exploring the functions of magnetic materials. This study involved the rapid preparation of a composition-gradient Fe–Co–Cr ternary thin film using a table-top sputtering system and 3D printer, followed by measurement of the chemical components and magnetic contrast by photoemission electron microscopy, through the acquisition of one million spectral datasets within 10 min. The ternary magnetic phase diagram of Fe–Co–Cr obtained by statistical analysis of the magnetic circular dichroism (MCD) contrast images was in perfect agreement with previous studies. The MCD histogram was fitted based on Landau theory, and the estimated critical exponent β (0.36 ± 0.028) showed excellent agreement with previous theoretical and experimental studies. This study successfully demonstrates universal physical parameter analysis that characterizes magnetic properties by a high-throughput approach combined with a simple experimental apparatus.


Author(s):  
Tomohiro Yasuda ◽  
Komori Taro ◽  
Haruka Mitarai ◽  
Syuta Honda ◽  
Sambit Ghosh ◽  
...  

Abstract The ferrimagnet Mn4N forms a family of compounds useful in spintronics. In a compound comprising non-magnetic and magnetic elements, one basically expects the compound to become ferromagnetic when the proportion of the magnetic element increases. Conversely, one does not expect ferromagnetism when the proportion of the non-magnetic element increases. Surprisingly, Mn4N becomes ferromagnetic at room temperature when the Mn content is decreased by the addition of In atoms, a non-magnetic element. X-ray magnetic circular dichroism measurement reveals that the magnetic moment of Mn atoms at face-centered sites, Mn(II), reverses between x = 0.15 and 0.27 and aligns parallel to that of Mn atoms at corner sites, Mn(I), at x = 0.27 and 0.41. The sign of the anomalous Hall resistivity also changes between x = 0.15 and 0.27 in accordance with the reversal of the magnetic moment of the Mn(II) atoms. These results are interpreted from first-principles calculation that the magnetic moment of Mn(II) sites which are the nearest neighbors to the In atom align to that of Mn(I) sites.


2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Camiel van Efferen ◽  
Jan Berges ◽  
Joshua Hall ◽  
Erik van Loon ◽  
Stefan Kraus ◽  
...  

AbstractIn the standard model of charge density wave (CDW) transitions, the displacement along a single phonon mode lowers the total electronic energy by creating a gap at the Fermi level, making the CDW a metal–insulator transition. Here, using scanning tunneling microscopy and spectroscopy and ab initio calculations, we show that VS2 realizes a CDW which stands out of this standard model. There is a full CDW gap residing in the unoccupied states of monolayer VS2. At the Fermi level, the CDW induces a topological metal-metal (Lifshitz) transition. Non-linear coupling of transverse and longitudinal phonons is essential for the formation of the CDW and the full gap above the Fermi level. Additionally, x-ray magnetic circular dichroism reveals the absence of net magnetization in this phase, pointing to coexisting charge and spin density waves in the ground state.


2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Xing Cheng ◽  
Zhixuan Cheng ◽  
Cong Wang ◽  
Minglai Li ◽  
Pingfan Gu ◽  
...  

AbstractTwo-dimensional magnetic semiconductors provide a platform for studying physical phenomena at atomically thin limit, and promise magneto-optoelectronic devices application. Here, we report light helicity detectors based on graphene-CrI3-graphene vdW heterostructures. We investigate the circularly polarized light excited current and reflective magnetic circular dichroism (RMCD) under various magnetic fields in both monolayer and multilayer CrI3 devices. The devices exhibit clear helicity-selective photoresponse behavior determined by the magnetic state of CrI3. We also find abnormal negative photocurrents at higher bias in both monolayer and multilayer CrI3. A possible explanation is proposed for this phenomenon. Our work reveals the interplay between magnetic and optoelectronic properties in CrI3 and paves the way to developing spin-optoelectronic devices.


2021 ◽  
Vol 92 (11) ◽  
pp. 113001
Author(s):  
Jake Sutcliffe ◽  
J. Olof Johansson

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