The characterization and analysis of magnetization dynamics and magnetic damping of antiferromagnetic magnons is important in the field of antiferromagnetic
spintronics. This is primarily because antiferromagnets have magnetic resonances in the THz range as compared to ferromagnetic resonance which tends to occur in the GHz range. In this
work, we employ frequency-domain THz spectroscopy to explore the antiferromagnetic resonance frequency associated with monocrystalline NiO [1]. Specifically, a continuous-wave THz
spectroscopy system is used to measure the antiferromagnetic resonance of three NiO cuts (111), (110), and (100). To find the absorption peak, a reference measurement is taken in addition
to the NiO measurement. Raw data from the reference and NiO can be visually compared to see two effects: the THz system instrument response and Fabry-Perot interference pattern.
During analysis, the instrument response and Fabry-Perot pattern are subtracted so that a clear absorption peak at the resonant frequency of NiO can be observed. An antiferromagnetic
resonance, near 1 THz, is seen in each cut of NiO. Our results demonstrate the utility of working in the frequency domain to characterize antiferromagnetic materials that will be used
eventually for ultrafast antiferromagnetic spintronic device technologies.<br>

**References:**<br>

[1] Moriyama, Takahiro, et al., Physical Review Materials 3.5, 051402 (2019)

Exploring antiferromagnetic resonances of NiO with frequency domain THz spectroscopy

Synthetic antiferromagnets (S-AFMs) have recently been shown to be ideal systems to search for Exceptional Points (EPs) [1]. In a S-AFM, EPs are the point at which the optical and acoustic magnons coalesce and are indistinguishable from one another. EPs can be reached by varying parameters, such as the exchange coupling between magnetic layers. Once an EP is reached, only a single magnon branch exists in the magnon energy spectrum, and this makes EPs an attractive prospect for controlling magnons in magnetic microstructures. Recently, we have computationally calculated and visualized EPs in S-AFMs using micromagnetic simulations [2]. We determined that dipolar interactions play a pivotal role in determining if and where EPs occur in the parameter space used to describe the S-AFM. Our results are both qualitatively and quantitatively different compared to macrospin models [3], where dipolar interactions are not considered. We are now investigating how the macrospin limit can be recovered in micromagnetic simulations if spacer layers are built into the simulation, or if the shape of the micromagnetic object is changed. By recovering the macrospin limit within micromagnetic simulations, we will demonstrate new geometric parameters that can be used to control EPs and the magnon energy spectrum within S-AFMs.<br/><br/>Work at Oakland University was supported by U.S. National Science Foundation under Award No. ECCS-1941426.

![](https://assets.underline.io/uploads/markdown_image/1/image/824acc503fd69f0ff6f80f24f5badeb6.jpg)

FIG. 1. (a) Illustration of two micromagnetic layers in antiferromagnetic alignment. A nonmagnetic spacer layer is represented by the grey section. (b) Magnon spectra shown when simulating the antiferromagnetic state with ferromagnetic interlayer exchange stiffness. No clear presence of an EP exists in the antiferromagnetic state before it becomes unstable due to the FM exchange stiffness.

Adjusting dipolar interactions to control exceptional points in synthetic antiferromagnets

ROA: Magnetic Characterization from Nano to Macro

technical paper

#### Welcome to the 67th Annual Conference on Magnetism and Magnetic Materials, MMM 2022!

The Conference was held from October 31 to November 4 and offers both in-person and on-demand content.

MMM 2022 is sponsored jointly by AIP Publishing and the IEEE Magnetics Society. Members of the international scientific and engineering communities interested in recent developments in fundamental and applied magnetism are invited to attend and contribute to the technical sessions. The technical program will include invited and contributed papers in oral and poster sessions, invited symposia, a tutorial, and several special sessions. This Conference provides an outstanding opportunity for worldwide participants to meet their colleagues and collaborators and discuss developments in all areas of magnetism research.

<iframe width="560" height="315" src="https://s3.amazonaws.com/pf-user-files-01/u-59356/uploads/2022-11-02/un13zp7/MMM%20Welcome%20Video%20v5.mp4" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe> <br>



For tickets to the event, please register at the following link: https://magnetism.org/registration

Please register for the MMM 2022 conference to join the event.

MMM 2022

This Conference provides an outstanding opportunity for worldwide participants to meet their colleagues and collaborators and discuss developments in all areas of magnetism research.

**Session chair:** Oleksii Volkov, Helmholtz-Zentrum Dresden-Rossendorf



HOL - Spin Waves and Magnetization Dynamics II

The 15th Joint MMM-INTERMAG Conference (2022 Joint) is sponsored jointly by AIP Publishing and the IEEE Magnetics Society. Members of the international scientific and engineering communities interested in recent developments in fundamental and applied magnetism are invited to attend and contribute to the technical sessions. The technical program will include invited and contributed papers in oral and poster sessions, invited symposia, a plenary session, and an evening session, with about 1500 presentations overall. This Conference provides an outstanding opportunity for worldwide participants to meet their colleagues and collaborators and discuss developments in all areas of magnetism research.

The 2022 Joint Conference will offer both in-person and prerecorded on-demand content.

For tickets to the event, please register at the following link: https://magnetism.org/register

Teresa Jeffrey

2

3

SHORT BIO

Presentations

Exploring antiferromagnetic resonances of NiO with frequency domain THz spectroscopy

Adjusting dipolar interactions to control exceptional points in synthetic antiferromagnets

Stay up to date with the latest Underline news!

PRESENTATIONS

CONFERENCES

COMPANY

RESOURCES