http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Antiferromagnetic Insulatronics: Spintronics without magnetic fields
Mathias Klaui 한국자기학회 2021 한국자기학회 학술연구발표회 논문개요집 Vol.31 No.1
While known for a long time, antiferromagnetically ordered systems have previously been considered, as expressed by Louis Néel in his Nobel Prize Lecture, to be “interesting but useless”. However, since antiferromagnets potentially promises faster operation, enhanced stability with respect to interfering magnetic fields and higher integration due to the absence of dipolar coupling, they could potentially become a game changer for new spintronic devices. We recently realized switching in the metallic antiferromagnet Mn<sub>2</sub>Au by intrinsic staggered spin-orbit torques [1,2] and characterize the switching properties by direct imaging. While switching by staggered intrinsic spin-orbit torques in metallic AFMs requires special structural asymmetry, interfacial non-staggered spin-orbit torques can switch multilayers of many insulating AFMs capped with heavy metal layers [3-5]. Furthermore electric fields can be used to generate strain to switch the AFM order parameter [6]. To read out the information, we demonstrate that we can obtain ultra-strong coupling from AFMs to ferromagnetic layers. This coupling leads to a perfect 1-to-1 imprinting of the AFM domain structure into the ferromagnet and read-out via established magnetoresistance effects (under review). Finally, we study transport of spin in antiferromagnets. While typically spin transport length scales of a few nm have been reported for AFMs, for hematite, we find in a non-local geometry that spin transport of tens of micrometers is possible [7,8]. We detect a first harmonic signal, related to the spin conductance, that exhibits a maximum at the spin-flop reorientation, while the second harmonic signal, related to the Spin Seebeck conductance, is linear in the amplitude of the applied magnetic field [7]. The first signal is dependent on the direction of the Néel vector and the second one depends on the induced magnetic moment due to the field. Recently we also achieved transport in the easy plane phase [9], which allows us to obtain long distance spin transport in hematite even at room temperature [9,10]. This particular transport regime relies on the superposition of linearly polarized magnons to transport spin leading to a special field dependence of the transported spin polarization.
Mathias Klaui,Dennis Ilgaz,Lutz Heyne,June-Seo Kim,Olivier Boulle,Christine Schieback,Fabian Zinser,Stephen Krzyk,Mikhail Fonin,Ulrich Rudiger,Dirk Backes,Laura J. Heyderman,T. O. Mentes,A. Locatelli 한국자기학회 2009 Journal of Magnetics Vol.14 No.2
Herein, different concepts for domain wall propagation based on currents and fields that could potentially be used in magnetic data storage devices based on domains and domain walls are reviewed. By direct imaging, we show that vortex and transverse walls can be displaced using currents due to the spin transfer torque effect. For the case of field-induced wall motion, particular attention is paid to the influence of localized fields and local heating on the depinning and propagation of domain walls. Using an Au nanowire adjacent to a permalloy structure with a domain wall, the depinning field of the wall, when current pulses are injected into the Au nanowire, was studied. The current pulse drastically modified the depinning field, which depended on the interplay between the externally applied field direction and polarity of the current, leading subsequently to an Oersted field and heating of the permalloy at the interface with the Au wire. Placing the domain wall at various distances from the Au wire and studying different wall propagation directions, the range of Joule heating and Oersted field was determined; both effects could be separated. Approaches beyond conventional field- and current-induced wall displacement are briefly discussed.