We propose a hybrid coercivity mechanism for exchange-coupled hard/soft multilayers, which incorporates elements of both the traditional nucleation and pinning mechanisms based on both threedimensional(3 D) and one-di...We propose a hybrid coercivity mechanism for exchange-coupled hard/soft multilayers, which incorporates elements of both the traditional nucleation and pinning mechanisms based on both threedimensional(3 D) and one-dimensional(1 D) micromagnetic calculations. The magnetic reversal starts with the nucleation of the domain wall near the defects or soft phases, which ends by the pinning usually in the same place. Therefore, pinning near the nucleation centers are the dominant coercivity mechanism for both exchange-coupled nanocomposites and so-called single-phased permanent magnets. Our proposed coercivity mechanism and calculated results agree very well with available experimental data,especially the recently reported high energy products achieved in NdFeB and SmCo based hard/soft multilayers. The hybrid coercivity mechanism can be readily extended to single-phased permanent magnets with defects and other magnetic systems.展开更多
Hard/soft permanent magnets have attracted a lot of attention because of their rich magnetic properties and their potential for realizing giant energy products. However, energy products obtained by scientists in exper...Hard/soft permanent magnets have attracted a lot of attention because of their rich magnetic properties and their potential for realizing giant energy products. However, energy products obtained by scientists in experiments are much smaller than the theoretical values, which has been studied by various analytical and numerical methods. The famous Stoner-Wohlfarth model(S-W model) is too simple to give the hysteresis loops whereas the intensively used variational method is too complicated to reveal the underlying mechanism in a simple form. The analytical model proposed in this paper maintains a balance between simplicity and precision, where the spins in the soft layer rotate fast and coherently with the applied field while those in the hard layer response to the applied field much slower but also coherent. An exchange coupling is provided to maintain the exchange spring which drags the spins in the hard layer to follow those in the soft layer. Similar to the more sophisticated model, the calculated hysteresis loops display three typical magnetic phases, i.e., the rigid composite magnet, the exchange spring and decoupled magnet, whereas the simple SW model can only give one single phase, i.e., the rigid composite one. In addition to the hysteresis loop, the energy product and the nucleation fields have been calculated and compared with those calculated by other methods, which justifies our model.Careful comparisons show that our calculations are in good agreement with the experimental results and other theoretical results, especially for the important coercivity value and the related mechanism.展开更多
A magnetic bimeron is an in-plane topological counterpart of a magnetic skyrmion.Despite the topological equivalence,their statics and dynamics could be distinct,making them attractive from the perspectives of both ph...A magnetic bimeron is an in-plane topological counterpart of a magnetic skyrmion.Despite the topological equivalence,their statics and dynamics could be distinct,making them attractive from the perspectives of both physics and spintronic applications.In this work,we demonstrate the stabilization of bimeron solitons and clusters in the antiferromagnetic(AFM)thin film with interfacial Dzyaloshinskii–Moriya interaction(DMI).Bimerons demonstrate high current-driven mobility as generic AFM solitons,while featuring anisotropic and relativistic dynamics excited by currents with in-plane and out-ofplane polarizations,respectively.Moreover,these spin textures can absorb other bimeron solitons or clusters along the translational direction to acquire a wide range of Néel topological numbers.The clustering involves the rearrangement of topological structures,and gives rise to remarkable changes in static and dynamical properties.The merits of AFM bimeron clusters reveal a potential path to unify multibit data creation,transmission,storage,and even topology-based computation within the same material system,and may stimulate spintronic devices enabling innovative paradigms of data manipulations.展开更多
基金Project supported by National Natural Science Foundation of China(51771127,51571126,51772004)
文摘We propose a hybrid coercivity mechanism for exchange-coupled hard/soft multilayers, which incorporates elements of both the traditional nucleation and pinning mechanisms based on both threedimensional(3 D) and one-dimensional(1 D) micromagnetic calculations. The magnetic reversal starts with the nucleation of the domain wall near the defects or soft phases, which ends by the pinning usually in the same place. Therefore, pinning near the nucleation centers are the dominant coercivity mechanism for both exchange-coupled nanocomposites and so-called single-phased permanent magnets. Our proposed coercivity mechanism and calculated results agree very well with available experimental data,especially the recently reported high energy products achieved in NdFeB and SmCo based hard/soft multilayers. The hybrid coercivity mechanism can be readily extended to single-phased permanent magnets with defects and other magnetic systems.
基金Project supported by National Natural Science Foundation of China(11074179,51771127,51571126,51772004)the Scientific Research Fund of Sichuan Provincial Education Department(18TD0010,16CZ0006)
文摘Hard/soft permanent magnets have attracted a lot of attention because of their rich magnetic properties and their potential for realizing giant energy products. However, energy products obtained by scientists in experiments are much smaller than the theoretical values, which has been studied by various analytical and numerical methods. The famous Stoner-Wohlfarth model(S-W model) is too simple to give the hysteresis loops whereas the intensively used variational method is too complicated to reveal the underlying mechanism in a simple form. The analytical model proposed in this paper maintains a balance between simplicity and precision, where the spins in the soft layer rotate fast and coherently with the applied field while those in the hard layer response to the applied field much slower but also coherent. An exchange coupling is provided to maintain the exchange spring which drags the spins in the hard layer to follow those in the soft layer. Similar to the more sophisticated model, the calculated hysteresis loops display three typical magnetic phases, i.e., the rigid composite magnet, the exchange spring and decoupled magnet, whereas the simple SW model can only give one single phase, i.e., the rigid composite one. In addition to the hysteresis loop, the energy product and the nucleation fields have been calculated and compared with those calculated by other methods, which justifies our model.Careful comparisons show that our calculations are in good agreement with the experimental results and other theoretical results, especially for the important coercivity value and the related mechanism.
基金X.L.acknowledges the support by the Guangdong Basic and Applied Basic Research Foundation(Grant No.2019A1515111110)X.Z.acknowledges the support by the National Natural Science Foundation of China(Grant No.12004320)+15 种基金the Guangdong Basic and Applied Basic Research Foundation(Grant No.2019A1515110713)Presidential Postdoctoral Fellowship of The Chinese University of Hong Kong,Shenzhen(CUHKSZ)M.E.acknowledges the support from the Grants-in-Aid for Scientific Research from JSPS KAKENHI(Grant Nos.JP18H03676,JP17K05490,and JP15H05854)the support from CREST,JST(Grant Nos.JPMJCR16F1 and JPMJCR1874)O.A.T.acknowledges the support by the Australian Research Council(Grant No.DP200101027)the Cooperative Research Project Program at the Research Institute of Electrical Communication,Tohoku University(Japan),and by the Ministry of Science and Technology Higher Education of the Russian Federation in the framework of Increase Competitiveness Program of NUST“MISiS”(No.K2-2019-006)implemented by a governmental decree dated 16th of March 2013,N 211.X.X.acknowledges the support from the National Natural Science Foundation of China(51871137 and 61434002)the National Key R&D Program of China(2017YFB0405604)M.M.and M.K.acknowledge support from National Science Center of Poland No.2018/30/Q/ST3/00416Y.Z.acknowledges the support by the President’s Fund of CUHKSZ,Longgang Key Laboratory of Applied Spintronics,National Natural Science Foundation of China(Grant Nos.11974298 and 61961136006)Shenzhen Fundamental Research Fund(Grant No.JCYJ20170410171958839)Shenzhen Peacock Group Plan(Grant No.KQTD20180413181702403)Y.X.acknowledges the support by the State Key Program for Basic Research of China(Grant No.2014CB921101,2016YFA0300803)NSFC(Grants No.61427812,11574137)Jiangsu NSF(BK20140054)Jiangsu Shuangchuang Team Program and the UK EPSRC(EP/G010064/1).
文摘A magnetic bimeron is an in-plane topological counterpart of a magnetic skyrmion.Despite the topological equivalence,their statics and dynamics could be distinct,making them attractive from the perspectives of both physics and spintronic applications.In this work,we demonstrate the stabilization of bimeron solitons and clusters in the antiferromagnetic(AFM)thin film with interfacial Dzyaloshinskii–Moriya interaction(DMI).Bimerons demonstrate high current-driven mobility as generic AFM solitons,while featuring anisotropic and relativistic dynamics excited by currents with in-plane and out-ofplane polarizations,respectively.Moreover,these spin textures can absorb other bimeron solitons or clusters along the translational direction to acquire a wide range of Néel topological numbers.The clustering involves the rearrangement of topological structures,and gives rise to remarkable changes in static and dynamical properties.The merits of AFM bimeron clusters reveal a potential path to unify multibit data creation,transmission,storage,and even topology-based computation within the same material system,and may stimulate spintronic devices enabling innovative paradigms of data manipulations.