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Qian X, Yu G, Zhou N. Nonsteady dynamics at the dynamic depinning transition in the two-dimensional Gaussian random-field Ising model. Phys Rev E 2023; 107:064108. [PMID: 37464630 DOI: 10.1103/physreve.107.064108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Accepted: 05/17/2023] [Indexed: 07/20/2023]
Abstract
With large-scale Monte Carlo simulations, we investigate the nonsteady relaxation at the dynamic depinning transition in the two-dimensional Gaussian random-field Ising model. The dynamic scaling behavior is carefully analyzed, and the transition fields as well as static and dynamic exponents are accurately determined based on the short-time dynamic scaling form. Different from the usual assumption, two distinguished growth processes of spatial correlation lengths for the velocity and height of the domain wall are found. Thus, the universality class of the depinning transition is established, which significantly differs from that of the quenched disorder equation but agrees with that of the recent experiment as well as other simulations works. Under the influence of the mesoscopic time regime, the crossover from the second-order phase transition to the first-order one is confirmed in the weak-disorder regime, yielding an abnormal disorder-dependent nature of the criticality.
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Affiliation(s)
- Xiaohui Qian
- School of Physics, Hangzhou Normal University, Hangzhou 311121, China
| | - Gaotian Yu
- School of Physics, Hangzhou Normal University, Hangzhou 311121, China
| | - Nengji Zhou
- School of Physics, Hangzhou Normal University, Hangzhou 311121, China
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Gao ZC, Su Y, Xi B, Hu J, Park C. The origin of spin wave pulse-induced domain wall inertia. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:475803. [PMID: 32870813 DOI: 10.1088/1361-648x/abae1a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Accepted: 08/11/2020] [Indexed: 06/11/2023]
Abstract
The fundamental problem of domain wall (DW) inertia-the property that gives to inertial behaviors remains unclear in the physics of magnetic solitons. To understand its nature as well as to achieve accurate DW positioning and efficient manipulation of domain wall motion (DWM), spin wave (SW) pulse-induced DW transient effect is studied both numerically and theoretically in a magnetic nanostrip. It is shown for the first time that there occurs inevitable deceleration/automotion after SW pulse, which indicates nonzero DW inertia. The induced DWM is revealed to relate to two factors: energy storing within DW and out-of-plane tilting of DW. To explain the DWM dynamics, a one-dimensional collective model is developed to account for the excitation of spin wave pulse. The model successfully bridges DW energy, DW tilting and DW displacement and provides descriptions in accordance with numerical findings. It is made clear that the DW automotion hence DW inertia originate from the process of DW relaxation toward equilibrium. The DW inertia is expressed in terms of effective mass and turns out to be a time-dependent function with damping constantαas the governing parameter, which opposes the nature of intrinsic mass. For case containing multiple DWs, the total effective mass is shown to concern the reached velocity and stored energy of DWs instead of the number of DWs, which is against common intuition.
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Affiliation(s)
- Zhong-Chen Gao
- School of Physical Science and Technology, Yangzhou University, Yangzhou 225002, People's Republic of China
- Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Republic of Korea
| | - Yuanchang Su
- School of Physical Science and Technology, Yangzhou University, Yangzhou 225002, People's Republic of China
| | - Bin Xi
- School of Physical Science and Technology, Yangzhou University, Yangzhou 225002, People's Republic of China
| | - Jingguo Hu
- School of Physical Science and Technology, Yangzhou University, Yangzhou 225002, People's Republic of China
| | - Chan Park
- Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Republic of Korea
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Islam MT, Wang XS, Wang XR. Thermal gradient driven domain wall dynamics. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:455701. [PMID: 31174196 DOI: 10.1088/1361-648x/ab27d6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The issue of whether a thermal gradient acts like a magnetic field or an electric current in the domain wall (DW) dynamics is investigated. Broadly speaking, magnetization control knobs can be classified as energy-driving or angular-momentum driving forces. DW propagation driven by a static magnetic field is the best known example of the former in which the DW speed is proportional to the energy dissipation rate, and the current-driven DW motion is an example of the latter. Here we show that DW propagation speed driven by a thermal gradient can be fully explained as the angular momentum transfer between thermally generated spin current and DW. We found DW-plane rotation speed increases as DW width decreases. Both DW propagation speed along the wire and DW-plane rotation speed around the wire decrease with the Gilbert damping. These facts are consistent with the angular momentum transfer mechanism, but are distinct from the energy dissipation mechanism. We further show that magnonic spin-transfer torque (STT) generated by a thermal gradient has both damping-like and field-like components. By analyzing DW propagation speed and DW-plane rotational speed, the coefficient ([Formula: see text]) of the field-like STT arising from the non-adiabatic process, is obtained. It is found that [Formula: see text] does not depend on the thermal gradient; increases with uniaxial anisotropy [Formula: see text] (thinner DW); and decreases with the damping, in agreement with the physical picture that a larger damping or a thicker DW leads to a better alignment between the spin-current polarization and the local magnetization, or a better adiabaticity.
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Affiliation(s)
- M T Islam
- Physics Department, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong Special Administrative Region of China. Physics Discipline, Khulna University, Khulna, Bangladesh
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Zhang GP, Bai YH, George TF. Is perpendicular magnetic anisotropy essential to all-optical ultrafast spin reversal in ferromagnets? JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:425801. [PMID: 28770812 DOI: 10.1088/1361-648x/aa83c6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
All-optical spin reversal presents a new opportunity for spin manipulations, free of a magnetic field. Most of all-optical-spin-reversal ferromagnets are found to have a perpendicular magnetic anisotropy (PMA), but it has been unknown whether PMA is necessary for spin reversal. Here we theoretically investigate magnetic thin films with either PMA or in-plane magnetic anisotropy (IMA). Our results show that spin reversal in IMA systems is possible, but only with a longer laser pulse and within a narrow laser parameter region. Spin reversal does not show a strong helicity dependence where the left- and right-circularly polarized light lead to the identical results. By contrast, the spin reversal in PMA systems is robust, provided both the spin angular momentum and laser field are strong enough while the magnetic anisotropy itself is not too strong. This explains why experimentally the majority of all-optical spin-reversal samples are found to have strong PMA and why spins in Fe nanoparticles only cant out of plane. It is the laser-induced spin-orbit torque that plays a key role in the spin reversal. Surprisingly, the same spin-orbit torque results in laser-induced spin rectification in spin-mixed configuration, a prediction that can be tested experimentally. Our results clearly point out that PMA is essential to spin reversal, though there is an opportunity for in-plane spin reversal.
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Affiliation(s)
- G P Zhang
- Department of Physics, Indiana State University, Terre Haute, IN 47809, United States of America
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Janda T, Roy PE, Otxoa RM, Šobáň Z, Ramsay A, Irvine AC, Trojanek F, Surýnek M, Campion RP, Gallagher BL, Němec P, Jungwirth T, Wunderlich J. Inertial displacement of a domain wall excited by ultra-short circularly polarized laser pulses. Nat Commun 2017; 8:15226. [PMID: 28513588 PMCID: PMC5442316 DOI: 10.1038/ncomms15226] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Accepted: 03/10/2017] [Indexed: 11/09/2022] Open
Abstract
Domain wall motion driven by ultra-short laser pulses is a pre-requisite for envisaged low-power spintronics combining storage of information in magnetoelectronic devices with high speed and long distance transmission of information encoded in circularly polarized light. Here we demonstrate the conversion of the circular polarization of incident femtosecond laser pulses into inertial displacement of a domain wall in a ferromagnetic semiconductor. In our study, we combine electrical measurements and magneto-optical imaging of the domain wall displacement with micromagnetic simulations. The optical spin-transfer torque acts over a picosecond recombination time of the spin-polarized photo-carriers that only leads to a deformation of the initial domain wall structure. We show that subsequent depinning and micrometre-distance displacement without an applied magnetic field or any other external stimuli can only occur due to the inertia of the domain wall. Domain wall motion driven by ultra-short laser pulses has potential for storage of information in magnetoelectronic devices. Here the authors demonstrate the conversion of a circularly polarized femtosecond laser light into inertial displacement of a domain wall in a ferromagnetic semiconductor.
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Affiliation(s)
- T Janda
- Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, 121 16 Prague 2, Czech Republic.,Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnická 10, 162 00 Praha 6, Czech Republic
| | - P E Roy
- Hitachi Cambridge Laboratory, J. J. Thomson Avenue, Cambridge CB3 0HE, UK
| | - R M Otxoa
- Hitachi Cambridge Laboratory, J. J. Thomson Avenue, Cambridge CB3 0HE, UK
| | - Z Šobáň
- Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnická 10, 162 00 Praha 6, Czech Republic
| | - A Ramsay
- Hitachi Cambridge Laboratory, J. J. Thomson Avenue, Cambridge CB3 0HE, UK
| | - A C Irvine
- Microelectronics Research Center, Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK
| | - F Trojanek
- Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, 121 16 Prague 2, Czech Republic
| | - M Surýnek
- Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, 121 16 Prague 2, Czech Republic
| | - R P Campion
- School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK
| | - B L Gallagher
- School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK
| | - P Němec
- Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, 121 16 Prague 2, Czech Republic
| | - T Jungwirth
- Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnická 10, 162 00 Praha 6, Czech Republic.,School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK
| | - J Wunderlich
- Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnická 10, 162 00 Praha 6, Czech Republic.,Hitachi Cambridge Laboratory, J. J. Thomson Avenue, Cambridge CB3 0HE, UK
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Optical-helicity-driven magnetization dynamics in metallic ferromagnets. Nat Commun 2017; 8:15085. [PMID: 28416803 PMCID: PMC5399298 DOI: 10.1038/ncomms15085] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2016] [Accepted: 02/23/2017] [Indexed: 11/08/2022] Open
Abstract
Recent observations of switching of magnetic domains in ferromagnetic metals by circularly polarized light, so-called all-optical helicity dependent switching, has renewed interest in the physics that governs the interactions between the angular momentum of photons and the magnetic order parameter of materials. Here we use time-resolved-vectorial measurements of magnetization dynamics of thin layers of Fe, Ni and Co driven by picosecond duration pulses of circularly polarized light. We decompose the torques that drive the magnetization into field-like and spin-transfer components that we attribute to the inverse Faraday effect and optical spin-transfer torque, respectively. The inverse Faraday effect is approximately the same in Fe, Ni and Co, but the optical spin-transfer torque is strongly enhanced by adding a Pt capping layer. Our work provides quantitative data for testing theories of light-material interactions in metallic ferromagnets and multilayers.
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