Ultrafast heating as a sufficient stimulus for magnetization reversal in a ferrimagnet.
TL;DR: Numerically and experimentally a novel mechanism of deterministic magnetization reversal in a ferrimagnet driven by an ultrafast heating of the medium resulting from the absorption of a sub-picosecond laser pulse without the presence of a magnetic field is shown.
Abstract: The question of how, and how fast, magnetization can be reversed is a topic of great practical interest for the manipulation and storage of magnetic information. It is generally accepted that magnetization reversal should be driven by a stimulus represented by time-non-invariant vectors such as a magnetic field, spin-polarized electric current, or cross-product of two oscillating electric fields. However, until now it has been generally assumed that heating alone, not represented as a vector at all, cannot result in a deterministic reversal of magnetization, although it may assist this process. Here we show numerically and demonstrate experimentally a novel mechanism of deterministic magnetization reversal in a ferrimagnet driven by an ultrafast heating of the medium resulting from the absorption of a sub-picosecond laser pulse without the presence of a magnetic field.
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University of California, Berkeley1, Argonne National Laboratory2, University of California, Los Angeles3, Massachusetts Institute of Technology4, University of California, San Diego5, University of Minnesota6, University of Texas at Austin7, Cornell University8, University of South Florida9, Stanford University10, University of California, Santa Cruz11, Ohio State University12, University of Nottingham13, Academy of Sciences of the Czech Republic14, Radboud University Nijmegen15, Eindhoven University of Technology16, University of California, Irvine17, Drexel University18, Northwestern University19, Pennsylvania State University20, Oakland University21, National Institute of Standards and Technology22, Johns Hopkins University23, University of Denver24
TL;DR: This article reviews static and dynamic interfacial effects in magnetism, focusing on interfacially-driven magnetic effects and phenomena associated with spin-orbit coupling and intrinsic symmetry breaking at interfaces, identifying the most exciting new scientific results and pointing to promising future research directions.
Abstract: This article reviews static and dynamic interfacial effects in magnetism, focusing on interfacially-driven magnetic effects and phenomena associated with spin-orbit coupling and intrinsic symmetry breaking at interfaces. It provides a historical background and literature survey, but focuses on recent progress, identifying the most exciting new scientific results and pointing to promising future research directions. It starts with an introduction and overview of how basic magnetic properties are affected by interfaces, then turns to a discussion of charge and spin transport through and near interfaces and how these can be used to control the properties of the magnetic layer. Important concepts include spin accumulation, spin currents, spin transfer torque, and spin pumping. An overview is provided to the current state of knowledge and existing review literature on interfacial effects such as exchange bias, exchange spring magnets, spin Hall effect, oxide heterostructures, and topological insulators. The article highlights recent discoveries of interface-induced magnetism and non-collinear spin textures, non-linear dynamics including spin torque transfer and magnetization reversal induced by interfaces, and interfacial effects in ultrafast magnetization processes.
758 citations
TL;DR: The key methods used in atomistic spin models are presented, which are then applied to a range of magnetic problems, and the parallelization strategies used enable the routine simulation of extended systems with full atomistic resolution.
Abstract: Atomistic modelling of magnetic materials provides unprecedented detail about the underlying physical processes that govern their macroscopic properties, and allows the simulation of complex effects such as surface anisotropy, ultrafast laser-induced spin dynamics, exchange bias, and microstructural effects. Here we present the key methods used in atomistic spin models which are then applied to a range of magnetic problems. We detail the parallelization strategies used which enable the routine simulation of extended systems with full atomistic resolution.
623 citations
TL;DR: This work demonstrates optical control of ferromagnetic materials ranging from magnetic thin films to multilayers and even granular films being explored for ultra-high-density magnetic recording, and shows that Optical control of magnetic materials is a much more general phenomenon than previously assumed.
Abstract: The interplay of light and magnetism allowed light to be used as a probe of magnetic materials. Now the focus has shifted to use polarized light to alter or manipulate magnetism. Here, we demonstrate optical control of ferromagnetic materials ranging from magnetic thin films to multilayers and even granular films being explored for ultra-high-density magnetic recording. Our finding shows that optical control of magnetic materials is a much more general phenomenon than previously assumed and may have a major impact on data memory and storage industries through the integration of optical control of ferromagnetic bits.
549 citations
TL;DR: It is demonstrated that all-optical helicity-dependent switching (AO-HDS) can be observed not only in selected rare earth-transition metal alloy films but also in a much broader variety of materials, including RE-TM alloys, multilayers and heterostructures.
Abstract: A promising strategy for achieving information storage devices with low energy consumption is to avoid using applied magnetic fields as a means to manipulate the magnetization of materials. Now, the class of materials that can be switched by all-optical means is shown to extend beyond alloys consisting of rare earths and transition metals.
531 citations
TL;DR: Optical manipulation of magnetic order by femtosecond laser pulses has developed into an exciting and still expanding research field that keeps being fueled by a continuous stream of new and sometimes counterintuitive results, which may also potentially revolutionize data storage and information processing technologies.
Abstract: This review discusses the recent studies of magnetization dynamics and the role of angular momentum in thin films of ferrimagnetic rare-earth-transition metal (RE-TM) alloys, e.g. GdFeCo, where both magnetization and angular momenta are temperature dependent. It has been experimentally demonstrated that the magnetization can be manipulated and even reversed by a single 40 fs laser pulse, without any applied magnetic field. This switching is found to follow a novel reversal pathway, that is shown however to depend crucially on the net angular momentum, reflecting the balance of the two opposite sublattices. In particular, optical excitation of ferrimagnetic GdFeCo on a time scale pertinent to the characteristic time of the exchange interaction between the RE and TM spins, i.e. on the time scale of tens of femtoseconds, pushes the spin dynamics into a yet unexplored regime, where the two exchange-coupled magnetic sublattices demonstrate substantially different dynamics. As a result, the reversal of spins appears to proceed via a novel transient state characterized by a ferromagnetic alignment of the Gd and Fe magnetic moments, despite their ground-state antiferromagnetic coupling.Thus, optical manipulation of magnetic order by femtosecond laser pulses has developed into an exciting and still expanding research field that keeps being fueled by a continuous stream of new and sometimes counterintuitive results. Considering the progress in the development of plasmonic antennas and compact ultrafast lasers, optical control of magnetic order may also potentially revolutionize data storage and information processing technologies.
305 citations
References
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TL;DR: Magnetoelectric multiferroics combine ferromagnetic magnetization and ferroelectricity in the same phase and have tremendous potential for applications, not only because they possess the properties of both parent phenomena, but also because coupling between ferromagnetism and electric polarization can lead to additional novel effects as discussed by the authors.
Abstract: Magnetoelectric multiferroics combine ferromagnetism (a spontaneous magnetization that can be switched by a magnetic field) and ferroelectricity (a spontaneous electric polarization that can be switched by an electric field) in the same phase They have tremendous potential for applications, not only because they possess the properties of both parent phenomena, but also because coupling between ferromagnetism and ferroelectricity can lead to additional novel effects In their Perspective,
Spaldin and Fiebig
discuss the factors behind the recent resurgence of interest in magnetoelectric multiferroics, describe some exciting results emerging from the current research activities, and point to important challenges and directions for future work
2,523 citations
TL;DR: In this paper, the authors discuss the mathematical programming approach to frontier estimation known as Data Envelopment Analysis (DEA) and examine the effect of model orientation on the efficient frontier.
1,873 citations
02 Dec 2008
TL;DR: The challenges for heat-assisted magnetic recording are surveyed and the progress that has been made in addressing them are surveyed.
Abstract: Heat-assisted magnetic recording is a promising approach for enabling large increases in the storage density of hard disk drives. A laser is used to momentarily heat the recording area of the medium to reduce its coercivity below that of the applied magnetic field from the recording head. In such a system, the recording materials have a very high magnetic anisotropy, which is essential for the thermal stability of the magnetization of the extremely small grains in the medium. This technology involves new recording physics, new approaches to near field optics, a recording head that integrates optics and magnetics, new recording materials, lubricants that can withstand extremely high temperatures, and new approaches to the recording channel design. This paper surveys the challenges for this technology and the progress that has been made in addressing them.
1,121 citations
"Ultrafast heating as a sufficient s..." refers methods in this paper
...Numerical simulations also show that the field required to prevent reversal depends on the input parameters, for example, the coupling parameter (λi), as described by equation (4)....
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Journal Article•
1,053 citations
TL;DR: It is demonstrated that circularly polarized femtosecond laser pulses can be used to non-thermally excite and coherently control the spin dynamics in magnets by way of the inverse Faraday effect, and offers prospects for applications of ultrafast lasers in magnetic devices.
Abstract: The demand for ever-increasing density of information storage and speed of manipulation has triggered an intense search for ways to control the magnetization of a medium by means other than magnetic fields. Recent experiments on laser-induced demagnetization and spin reorientation use ultrafast lasers as a means to manipulate magnetization, accessing timescales of a picosecond or less. However, in all these cases the observed magnetic excitation is the result of optical absorption followed by a rapid temperature increase. This thermal origin of spin excitation considerably limits potential applications because the repetition frequency is limited by the cooling time. Here we demonstrate that circularly polarized femtosecond laser pulses can be used to non-thermally excite and coherently control the spin dynamics in magnets by way of the inverse Faraday effect. Such a photomagnetic interaction is instantaneous and is limited in time by the pulse width (approximately 200 fs in our experiment). Our finding thus reveals an alternative mechanism of ultrafast coherent spin control, and offers prospects for applications of ultrafast lasers in magnetic devices.
963 citations