Manipulating femtosecond spin-orbit torques with laser pulse sequences to control magnetic memory states and ringing

Lingos, P. C.; Wang, J.; Perakis, I. E.

doi:10.1103/physrevb.91.195203

Cited by 23 publications

(19 citation statements)

References 96 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…(6)). The process is similar to a recent study in a magnetic semiconductor by Lingos and coworkers [27] and in a more complicated magnetic system [28]. The module of spin is conserved, orṠ · S = 0, as seen from Eq.…”

supporting

confidence: 85%

A new and simple model for magneto-optics uncovers an unexpected spin switching

Zhang

Bai

George

2015

EPL

View full text Add to dashboard Cite

In magneto-optics the spin angular momentum Sz of a sample is indirectly probed by the rotation angle and ellipticity, which are mainly determined by the off-diagonal susceptibility χ (1) xy . A direct and analytic relation between Sz and χ (1) xy is necessary and of paramount importance to the success of magneto-optics, but is often difficult to acquire since quantum mechanically the relation is hidden in the sum-over-states. Here we propose a new and simple model to establish such a much needed relation. Our model is based on the Hookean model, but includes spin-orbit coupling. Under cw excitation, we show that χ (1) xy (ω) is indeed directly proportional to Sz for a fixed photon frequency ω. Such an elegant relation is encouraging, and we wonder whether our model can describe spin dynamics as well. By allowing the spin to change dynamically, to our surprise, our model predicts that an ultrafast laser pulse can induce a spin precession; with appropriate parameters, the laser can even reverse spin from one direction to another. This works for both the circularly and linearly polarized light. The spin reversal window is narrow. These unexpected results closely resemble all-optical helicity-dependent magnetic switching found in much more complicated ferrimagnetic rare earth compounds. Therefore, we believe that our spin-orbit coupled model may find some important applications in spin switching processes, a hot topic in femtomagnetism.Introduction. -Magneto-optical Faraday and Kerr techniques are indispensable to modern magnetism investigations [1,2]. Such a technique is an ideal tool to investigate both static and dynamic evolutions of spin [3][4][5][6], since it is a photon-in and photon-out technique and leaves the sample intact before and after the experimental measurement. The origin of the magneto-optics is rooted in the spin-orbit coupling and exchange interaction [7,8], where the rotational angle and ellipticity carry the information of the spin moment change. The classical understanding is developed through the harmonic oscillator model (Hookean model), augmented with the Lorentz force term [7,8],

show abstract

supporting

confidence: 85%

A new and simple model for magneto-optics uncovers an unexpected spin switching

Zhang

Bai

George

2015

EPL

View full text Add to dashboard Cite

show abstract

“…Non-thermal pumping of orbital transitions in the optical range is known to induce a nonlinear spin-charge coupling on ultrashort timescales 23,24 . In the terahertz spectral range, this concept can be applied to any material in which selected low-energy electronic transitions change the magnetic anisotropy, for example in oxides containing both 3d and 4f ions (for example, orthoferrites, manganites, garnets and ferroborates) and in 3d-compounds such as hematite α-Fe 2 O 3 .…”

mentioning

confidence: 99%

Nonlinear spin control by terahertz-driven anisotropy fields

et al. 2016

View full text Add to dashboard Cite

Future information technologies, such as ultrafast data recording, quantum computation or spintronics, call for ever faster spin control by light [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] . Intense terahertz pulses can couple to spins on the intrinsic energy scale of magnetic excitations 5,11 . Here, we explore a novel electric dipole-mediated mechanism of nonlinear terahertz-spin coupling that is much stronger than linear Zeeman coupling to the terahertz magnetic field 5,10 . Using the prototypical antiferromagnet thulium orthoferrite (TmFeO 3 ), we demonstrate that resonant terahertz pumping of electronic orbital transitions modifies the magnetic anisotropy for ordered Fe 3+ spins and triggers large-amplitude coherent spin oscillations. This mechanism is inherently nonlinear, it can be tailored by spectral shaping of the terahertz waveforms and its efficiency outperforms the Zeeman torque by an order of magnitude. Because orbital states govern the magnetic anisotropy in all transition-metal oxides, the demonstrated control scheme is expected to be applicable to many magnetic materials.Ultrafast magnetization control has become a key goal of modern photonics, with a broad variety of successful concepts emerging at a fast pace. Examples include light-induced spin reorientation in canted antiferromagnets 3 , vectorial control of magnetization by light 6 , photoinduced antiferromagnet-ferromagnet phase transitions 9 , optical modification of the exchange energy 4,14 and driving spin precessions via nonlinear magneto-phononic coupling 7,16 . Despite this remarkable progress, most of the photon energy in all known concepts using visible and near-infrared light is inactive with respect to the light-spin interaction, and avoiding dissipation of large excess energies requires special care.In contrast, intense electromagnetic pulses at terahertz frequencies may interface spin dynamics directly on their intrinsic energy scales 5,11 . The magnetic field component of few-cycle terahertz pulses has been used to coherently control magnons in the electronic ground state by direct Zeeman interaction 5,11 . Because magnetic dipole coupling is typically weak, however, terahertz-driven spin excitation has been confined to the linear response regime. Massive nonlinearities, such as terahertz-induced phase transitions 17,18 and terahertz lightwave electronics [19][20][21][22]

show abstract

“…Thus, through the spin-orbit coupling, the laser field increases the orbital angular momentum, and subsequently τ soc is boosted. For this reason, Tesavova et al [34] called τ soc the optical spinorbit torque, or femtosecond spin-orbit torque by Lingos et al [35].…”

mentioning

confidence: 99%

Switching ferromagnetic spins by an ultrafast laser pulse: Emergence of giant optical spin-orbit torque

Zhang¹,

Bai²,

George³

2016

EPL

View full text Add to dashboard Cite

-Faster magnetic recording technology is indispensable to massive data storage and big data sciences. All-optical spin switching offers a possible solution, but at present it is limited to a handful of expensive and complex rare-earth ferrimagnets. The spin switching in more abundant ferromagnets may significantly expand the scope of all-optical spin switching. Here by studying 40,000 ferromagnetic spins, we show that it is the optical spin-orbit torque that determines the course of spin switching in both ferromagnets and ferrimagnets. Spin switching occurs only if the effective spin angular momentum of each constituent in an alloy exceeds a critical value. Because of the strong exchange coupling, the spin switches much faster in ferromagnets than weakly-coupled ferrimagnets. This establishes a paradigm for all-optical spin switching. The resultant magnetic field (65 T) is so big that it will significantly reduce high current in spintronics, thus representing the beginning of photospintronics.

show abstract

Manipulating femtosecond spin-orbit torques with laser pulse sequences to control magnetic memory states and ringing

Cited by 23 publications

References 96 publications

A new and simple model for magneto-optics uncovers an unexpected spin switching

A new and simple model for magneto-optics uncovers an unexpected spin switching

Nonlinear spin control by terahertz-driven anisotropy fields

Switching ferromagnetic spins by an ultrafast laser pulse: Emergence of giant optical spin-orbit torque

Contact Info

Product

Resources

About