When a spin current is injected into an antiferromagnet, above a certain value of current, the Néel order precesses in a circular orbit about an axis oriented at an angle from the spin-polarization direction [1]. But below this value, for moderate values of damping, the motion evolves into chaos (aperiodic long-term behavior) for a small window of current, before settling down to equilibrium. We theoretically study the chaotic dynamics and emphasize its potential application in secure communication. Consider a uniaxial antiferromagnet whose easy axis is along z. Let the spin polarization make an angle ρ from the easy axis in the z-x plane. If at an instant, the Néel order n makes a polar angle θ from z and azimuthal angle φ from x, the equation of motion in the characteristic timescale of antiferromagnet for effective damping β and spin-current drive Γ is [1] θ″ + βθ′ - (φ′2 - 1)sin θ cos θ = -(Γ/2)sin φ sin ρ, φ″ + βφ′ + 2φ′θ′cot θ = (Γ/2)(cos ρ - cot θ cos φ sin ρ). The chaotic dynamics arises from the nonlinear structure of the flow in the four-dimensional phase space (θ, φ, θ′, φ′) from the initial condition (π/2, 0, 0, 0). For ρ = π/4 and β = 0.2 in specific, the steady-state behavior is static for Γ < 0.43, periodic for 0.43 < Γ < 0.44, chaotic for 0.44 < Γ < 0.5 and periodic for Γ > 0.5 as shown in Fig. 1. For other values of ρ and β, the chaos would occur for different values of Γ. The dynamics of Néel order in the antiferromagnet can reciprocally pump spin current into an adjacent conductor, proportional to the angular velocity ω = n x n′ shown in Fig. 2. This phenomenon may be exploited to detect and generate a chaotic electric signal at terahertz frequency, which may be used for communication via synchronized chaos. In this scheme, a louder chaos signal is used to mask the information-bearing signal and transmitted. The decryption utilizes the intended receiver’s ability to reproduce the chaos and subtract it from the mask.References: [1] A. Parthasarathy et al., arXiv:1911.00445 (2019).

Spin-torque-induced chaos in antiferromagnets

B2: Interdisciplinary Applications I

technical paper

The 65th Annual Conference on Magnetism and Magnetic Materials (MMM 2020) was held in a virtual form. The COVID-19 pandemic, with its associated uncertainty about international travel and the ability to gather in large groups, meant that the Steering Committee decided to cancel the face-to-face meeting that had been planned in Palm Beach, Florida November 2-6, 2020.

We were reluctant to give up the benefits of meeting face-to-face, and know that shifting to a virtual conference is a significant change for this community. Nevertheless, we are first and foremost concerned about the health and safety of all our Conference participants and their loved ones on returning home after travelling.

The MMM 2020 Steering Committee was working exceptionally hard, along with our sponsors, the IEEE Magnetics Society and AIP Publishing, to make this event serve the needs of our participants, who live in time zones all around the globe, in the best possible way. 

You need a ticket to explore this event.

If you have already registered for MMM 2020, and you have already created an account, then you
just need to login (above).

If you have already registered for MMM 2020, but you have not yet created an account, then you
need to click on &quot;create an account&quot; (above) and then login.

Forgot your password? Go to
https://www.underline.io/log-in

If you have not yet registered for MMM 2020 but would like to do so, go to
https://magnetism.org/register

Still need help? Contact our team!


Arun Parthasarathy

1

SHORT BIO

Presentations

Spin-torque-induced chaos in antiferromagnets

Stay up to date with the latest Underline news!

PRESENTATIONS

CONFERENCES

COMPANY

RESOURCES