npj SpintronicsPub Date : 2024-10-05DOI: 10.1038/s44306-024-00055-y
Philipp Keßler, Laura Garcia-Gassull, Andreas Suter, Thomas Prokscha, Zaher Salman, Dmitry Khalyavin, Pascal Manuel, Fabio Orlandi, Igor I. Mazin, Roser Valentí, Simon Moser
{"title":"Absence of magnetic order in RuO2: insights from μSR spectroscopy and neutron diffraction","authors":"Philipp Keßler, Laura Garcia-Gassull, Andreas Suter, Thomas Prokscha, Zaher Salman, Dmitry Khalyavin, Pascal Manuel, Fabio Orlandi, Igor I. Mazin, Roser Valentí, Simon Moser","doi":"10.1038/s44306-024-00055-y","DOIUrl":"10.1038/s44306-024-00055-y","url":null,"abstract":"Altermagnets are a novel class of magnetic materials, where magnetic order is staggered both in coordinate and momentum space. The metallic rutile oxide RuO2, long believed to be a textbook Pauli paramagnet, recently emerged as a putative workhorse altermagnet when resonant X-ray and neutron scattering studies reported nonzero magnetic moments and long-range collinear order. While some experiments seem consistent with altermagnetism, magnetic order in RuO2 remains controversial. We show that RuO2 is nonmagnetic, both in bulk and thin film. Muon spectroscopy complemented by density-functional theory finds at most 1.14 × 10−4 μB/Ru in bulk and at most 7.5 × 10−4 μB/Ru in 11 nm epitaxial films, at our spectrometers’ detection limit, and dramatically smaller than previously reported neutron results that were used to rationalize altermagnetic behavior. Our own neutron diffraction measurements on RuO2 single crystals identify multiple scattering as the source for the false signal in earlier studies.","PeriodicalId":501713,"journal":{"name":"npj Spintronics","volume":" ","pages":"1-8"},"PeriodicalIF":0.0,"publicationDate":"2024-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s44306-024-00055-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142383564","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
npj SpintronicsPub Date : 2024-10-01DOI: 10.1038/s44306-024-00044-1
V. D. Nguyen, S. Rao, K. Wostyn, S. Couet
{"title":"Recent progress in spin-orbit torque magnetic random-access memory","authors":"V. D. Nguyen, S. Rao, K. Wostyn, S. Couet","doi":"10.1038/s44306-024-00044-1","DOIUrl":"10.1038/s44306-024-00044-1","url":null,"abstract":"Spin-orbit torque magnetic random-access memory (SOT-MRAM) offers promise for fast operation and high endurance but faces challenges such as low switching current, reliable field free switching, and back-end of line manufacturing processes. We review recent advancements in perpendicular SOT-MRAM devices, emphasizing on material developments to enhance charge-spin conversion efficiency and large-scale device integration strategies. We also discuss the remaining challenges in achieving a single device with low switching current, reliable field free switching to unlock the full potential of SOT-MRAM technology.","PeriodicalId":501713,"journal":{"name":"npj Spintronics","volume":" ","pages":"1-15"},"PeriodicalIF":0.0,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s44306-024-00044-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142360067","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Mott materials: unsuccessful metals with a bright future","authors":"Alessandra Milloch, Michele Fabrizio, Claudio Giannetti","doi":"10.1038/s44306-024-00047-y","DOIUrl":"10.1038/s44306-024-00047-y","url":null,"abstract":"Achieving the full understanding and control of the insulator-to-metal transition in Mott materials is key for the next generation of electronics devices, with applications ranging from ultrafast transistors, volatile and non-volatile memories and artificial neurons for neuromorphic computing. In this work, we will review the state-of-the-art knowledge of the Mott transition, with specific focus on materials of relevance for actual devices, such as vanadium and other transition metal oxides and chalcogenides. We will emphasize the current attempts in controlling the Mott switching dynamics via the application of external voltage and electromagnetic pulses and we will discuss how the recent advances in time- and space-resolved techniques are boosting the comprehension of the firing process. The nature of the voltage/light-induced Mott switching is inherently different from what is attainable by the slower variation of thermodynamic parameters, thus offering promising routes to achieving the reversible and ultrafast control of conductivity and magnetism in Mott nanodevices.","PeriodicalId":501713,"journal":{"name":"npj Spintronics","volume":" ","pages":"1-10"},"PeriodicalIF":0.0,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s44306-024-00047-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142360068","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Hybrid magnon-phonon crystals","authors":"Liyang Liao, Jiacheng Liu, Jorge Puebla, Qiming Shao, Yoshichika Otani","doi":"10.1038/s44306-024-00052-1","DOIUrl":"10.1038/s44306-024-00052-1","url":null,"abstract":"Magnons and phonons are engineered in artificial lattices with tunable modes and band dispersions. Recent advance in magnon-phonon coupling shined a light on combining magnonic and phononic crystals as hybrid magnon-phonon crystals, benefit from the tunable magnon-phonon coupling, the time-reversal symmetry breaking of magnons, and the long lifetime of phonons. This perspective summarizes lattice-based mutual control of magnons and phonons, and proposes the opportunities provided by the hybrid magnon-phonon crystals.","PeriodicalId":501713,"journal":{"name":"npj Spintronics","volume":" ","pages":"1-6"},"PeriodicalIF":0.0,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s44306-024-00052-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142137874","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
npj SpintronicsPub Date : 2024-09-02DOI: 10.1038/s44306-024-00053-0
Theodoros Adamantopoulos, Maximilian Merte, Frank Freimuth, Dongwook Go, Lishu Zhang, Marjana Ležaić, Wanxiang Feng, Yugui Yao, Jairo Sinova, Libor Šmejkal, Stefan Blügel, Yuriy Mokrousov
{"title":"Spin and orbital magnetism by light in rutile altermagnets","authors":"Theodoros Adamantopoulos, Maximilian Merte, Frank Freimuth, Dongwook Go, Lishu Zhang, Marjana Ležaić, Wanxiang Feng, Yugui Yao, Jairo Sinova, Libor Šmejkal, Stefan Blügel, Yuriy Mokrousov","doi":"10.1038/s44306-024-00053-0","DOIUrl":"10.1038/s44306-024-00053-0","url":null,"abstract":"While the understanding of altermagnetism is still at a very early stage, it is expected to play a role in various fields of condensed matter research, for example spintronics, caloritronics and superconductivity. In the field of optical magnetism, it is still unclear to which extent altermagnets as a class can exhibit a distinct behavior. Here we choose RuO2, a prototype metallic altermagnet with a giant spin splitting, and CoF2, an experimentally known insulating altermagnet, to study the light-induced magnetism in rutile altermagnets from first-principles. We demonstrate that in the non-relativisic limit the allowed sublattice-resolved orbital response exhibits symmetries, imposed by altermagnetism, which lead to a drastic canting of light-induced moments. On the other hand, we find that inclusion of spin-orbit interaction enhances the overall effect drastically, introduces a significant anisotropy with respect to the light polarization and strongly suppresses the canting of induced moments. Remarkably, we observe that the moments induced by linearly-polarized laser pulses in light altermagnets can even exceed in magnitude those predicted for heavy ferromagnets exposed to circularly polarized light. By resorting to microscopic tools we interpret our results in terms of the altermagnetic spin splittings and of their reciprocal space distribution. Based on our findings, we speculate that optical excitations may provide a unique tool to switch and probe the magnetic state of rutile altermagnets.","PeriodicalId":501713,"journal":{"name":"npj Spintronics","volume":" ","pages":"1-10"},"PeriodicalIF":0.0,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s44306-024-00053-0.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142117952","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Enhanced exchange bias in all-oxide heterostructures with cation-ordered ferrimagnetic double-perovskite","authors":"Xiaofu Qiu, Zelin Wang, Hetian Chen, Yuhan Liang, Xiaoyu Jiang, Yujun Zhang, Jing Ma, Fangyuan Zhu, Tianxiang Nan, Zhen Chen, Di Yi","doi":"10.1038/s44306-024-00051-2","DOIUrl":"10.1038/s44306-024-00051-2","url":null,"abstract":"The realization and control of exchange bias (EB) are highly desirable for spintronic applications. All-oxide heterostructures comprised of ferromagnetic and antiferromagnetic/multiferroic oxides provide an ideal platform to enable the electric-field control of EB, promising for energy-efficient memory and logic devices. However, the low block temperature (TB) and small bias field (HEB) hinder further advances towards room-temperature applications. Here, we report an alternative approach to enhance the interface-induced EB by using ferrimagnetic double-perovskite with B-site cation ordering. In heterostructures comprised of double-perovskite Sr2FeReO6 (SFRO) and LaFeO3 (LFO), a high TB (about 250 K) and large HEB are observed, which is significantly larger than the counterparts with LFO and ferromagnetic oxides. Further analysis suggests that the cation-ordering and ferrimagnetic spin structure of the double-perovskite could contribute significantly to the enhanced exchanged bias when interfacing with G-type antiferromagnets. Our results open a new avenue for developing all-oxides heterostructures for future magnetic technologies.","PeriodicalId":501713,"journal":{"name":"npj Spintronics","volume":" ","pages":"1-6"},"PeriodicalIF":0.0,"publicationDate":"2024-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s44306-024-00051-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141973730","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
npj SpintronicsPub Date : 2024-08-13DOI: 10.1038/s44306-024-00046-z
Ruben Dario Gonzalez Betancourt, Jan Zubáč, Kevin Geishendorf, Philipp Ritzinger, Barbora Růžičková, Tommy Kotte, Jakub Železný, Kamil Olejník, Gunther Springholz, Bernd Büchner, Andy Thomas, Karel Výborný, Tomas Jungwirth, Helena Reichlová, Dominik Kriegner
{"title":"Anisotropic magnetoresistance in altermagnetic MnTe","authors":"Ruben Dario Gonzalez Betancourt, Jan Zubáč, Kevin Geishendorf, Philipp Ritzinger, Barbora Růžičková, Tommy Kotte, Jakub Železný, Kamil Olejník, Gunther Springholz, Bernd Büchner, Andy Thomas, Karel Výborný, Tomas Jungwirth, Helena Reichlová, Dominik Kriegner","doi":"10.1038/s44306-024-00046-z","DOIUrl":"10.1038/s44306-024-00046-z","url":null,"abstract":"Recently, MnTe was established as an altermagnetic material that hosts spin-polarized electronic bands as well as anomalous transport effects like the anomalous Hall effect. In addition to these effects arising from altermagnetism, MnTe also hosts other magnetoresistance effects. Here, we study the manipulation of the magnetic order by an applied magnetic field and its impact on the electrical resistivity. In particular, we establish which components of anisotropic magnetoresistance are present when the magnetic order is rotated within the hexagonal basal plane. Our experimental results, which are in agreement with our symmetry analysis of the magnetotransport components, showcase the existence of an anisotropic magnetoresistance linked to both the relative orientation of current and magnetic order, as well as crystal and magnetic order. Altermagnetism is manifested as a three-fold component in the transverse magnetoresistance which arises due to the anomalous Hall effect.","PeriodicalId":501713,"journal":{"name":"npj Spintronics","volume":" ","pages":"1-9"},"PeriodicalIF":0.0,"publicationDate":"2024-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s44306-024-00046-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141973748","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
npj SpintronicsPub Date : 2024-08-12DOI: 10.1038/s44306-024-00050-3
Takayuki Shiino, Phuoc Cao Van, Jong-Guk Choi, Geunwoo Kim, Jong-Ryul Jeong, Byong-Guk Park
{"title":"Unconventional angular dependence of spin-orbit torque-induced harmonic Hall resistance in Pt/YIG bilayers","authors":"Takayuki Shiino, Phuoc Cao Van, Jong-Guk Choi, Geunwoo Kim, Jong-Ryul Jeong, Byong-Guk Park","doi":"10.1038/s44306-024-00050-3","DOIUrl":"10.1038/s44306-024-00050-3","url":null,"abstract":"Spin-orbit torque (SOT), arising from spin-orbit coupling-induced spin currents, provides efficient control of magnetization. SOT characterization involving harmonic Hall resistances is typically done in low-current regimes, distinct from high-current regimes, where SOT-induced magnetization switching occurs. In this study, we investigate azimuthal angle (ϕ)-dependent harmonic Hall resistances of a Pt/yttrium iron garnet (YIG) layer across a wide range of measurement currents. Under low-current conditions, conventional ϕ-dependent Hall resistances are observed; the first harmonic Hall resistance exhibits sin 2ϕ behavior and the second harmonic Hall resistance comprises cos ϕ and cos 3ϕ terms. Interestingly, with increasing current, higher-order angular-dependent terms become non-negligible, referring to the sin 4ϕ and sin 6ϕ terms for the first harmonic and the cos 5ϕ and cos 7ϕ terms for the second harmonic Hall resistances. We attribute this unconventional angular dependence to the nonlinear response of magnetization direction to SOT, emphasizing its relevance to understanding the magnetization dynamics during SOT-induced switching under large currents.","PeriodicalId":501713,"journal":{"name":"npj Spintronics","volume":" ","pages":"1-5"},"PeriodicalIF":0.0,"publicationDate":"2024-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s44306-024-00050-3.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141973731","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
npj SpintronicsPub Date : 2024-08-02DOI: 10.1038/s44306-024-00045-0
Taekoo Oh, Naoto Nagaosa
{"title":"Unraveling the dynamics of magnetization in topological insulator-ferromagnet heterostructures via spin-orbit torque","authors":"Taekoo Oh, Naoto Nagaosa","doi":"10.1038/s44306-024-00045-0","DOIUrl":"10.1038/s44306-024-00045-0","url":null,"abstract":"Spin–orbit coupling is a relativistic effect coupling the orbital angular momentum with the spin, which determines the physical properties of condensed matter. For instance, the spin–orbit coupling strongly influences spin dynamics, opening the possibility for promising applications. The topological insulator–ferromagnet heterostructure is a typical example exhibiting spin dynamics driven by current-induced spin–orbit torque. Recent observations of the sign flip of Hall conductivity imply that the spin–orbit torque is strong enough to flip magnetization within this heterostructure. Motivated by this, our study elucidates the conditions governing spin flips by studying the magnetization dynamics. We establish that the interplay between spin-anisotropy and spin–orbit torque plays a crucial role in the magnetization dynamics. Furthermore, we categorize various modes of magnetization dynamics, constructing a comprehensive phase diagram across distinct energy scales, damping constants, and applied frequencies. We also consider the effect of a magnetic field on the magnetization dynamics. This research not only offers insights into controlling spin direction but also charts a new pathway to the practical application of spin–orbit coupled systems.","PeriodicalId":501713,"journal":{"name":"npj Spintronics","volume":" ","pages":"1-10"},"PeriodicalIF":0.0,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s44306-024-00045-0.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141968511","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
npj SpintronicsPub Date : 2024-08-02DOI: 10.1038/s44306-024-00049-w
Amal Aldarawsheh, Moritz Sallermann, Muayad Abusaa, Samir Lounis
{"title":"Current-driven dynamics of antiferromagnetic skyrmions: from skyrmion Hall effects to hybrid inter-skyrmion scattering","authors":"Amal Aldarawsheh, Moritz Sallermann, Muayad Abusaa, Samir Lounis","doi":"10.1038/s44306-024-00049-w","DOIUrl":"10.1038/s44306-024-00049-w","url":null,"abstract":"Antiferromagnetic (AFM) skyrmions have emerged as a highly promising avenue in the realm of spintronics, particularly for the development of advanced racetrack memory devices. A distinguishing feature of AFM skyrmions is the cancellation of their net topological charge, leading to an anticipated absence of the skyrmion Hall effect (SkHE). Here, we unveil that the latter is finite under the influence of spin-transfer torque, depending on the direction of the injected current impinging on intrinsic AFM skyrmions emerging in Cr/Pd/Fe trilayer on Ir(111) surface. Hinging on first principles combined with atomistic spin dynamics simulations, we identify the origin of the SkHE, which is due to the ellipticity of the skyrmions, and we uncover that FM skyrmions in the underlying Fe layer act as effective traps for AFM skyrmions, confining them and affecting their velocity. These findings hold significant promise for spintronic applications, the design of multi-purpose skyrmion tracks while advancing our understanding of AFM–FM skyrmion interactions and hybrid soliton dynamics in heterostructures.","PeriodicalId":501713,"journal":{"name":"npj Spintronics","volume":" ","pages":"1-9"},"PeriodicalIF":0.0,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s44306-024-00049-w.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141968510","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}