Micrometer diameter bilayers of 20 nm Permalloy/20 nm Cobalt Oxide deposited on nanomechanical resonators were used to investigate exchange bias effects. The mechanical compliances of two resonator axes were enhanced by severing one torsion arm, Figure 1, resulting in a unique three-axis resonator that responds resonantly to torques generated by a three-axis RF field [1]. Our technique permits simultaneous measurement of three orthogonal torque components. Measurements of the anisotropies associated with exchange bias effects have been made. First, at cryogenic temperatures, observations of shifted linear hysteresis loops confirm the presence of a positive exchange bias at the Py/CoO interface. A rotating DC bias field was used to probe in-plane anisotropies through the out-of-plane torque, as shown in Figure 2 (open circles). Training effects in both the linear and rotating hysteresis data were observed and show that most of the training occurs during the first half of the first loop, consistent with an athermal training mechanism [2]. The data from the rotating hysteresis loops were fit with parameters from a macrospin solution to the Landau-Lifshitz-Gilbert equation. In order to reproduce our observations standard anisotropy terms, a spin-flop coupling term [3], and a rotatable anisotropy axis [3,4] are introduced to the model. Each parameter of the exchange bias model accounts for specific features of the rotational loop. A unidirectional anisotropy asymmeterizes the extrema magnitudes. The orientation of the rotatable anisotropy axis with respect to the ferromagnetic magnetization introduces a one-fold rotational symmetry that would otherwise be at least two-fold. The spin-flop term influences the angular positions of the peaks in the torque curve.

![](https://assets.underline.io/uploads/markdown_image/1/image/904fce60d2079057eb98db71f95841b7.jpg)

Figure 1: Electron micrograph of a micromechanical device used for demonstration of the three-axis torque measurement technique. The arrows indicate the three orthogonal torsional displacements.

![](https://assets.underline.io/uploads/markdown_image/1/image/a6f1c83647a790b3299d22bf142cc7ae.jpg)

Figure 2: Thermomechanically calibrated experimental data of the z torque component (resonator at liquid nitrogen temperature). Data were recorded during a rotational hysteresis loop. Fits from macrospin solutions to the LLG equation are shown.



Three-axis torque investigation of exchange bias in a micromagnetic disk

The classical Einstein-de Haas (EdH) effect [1] is a AC mechanical torque arising from a time rate of change of net magnetization, and represents the intrinsic relationship between magnetism and mechanical angular momentum. Nanofabrication of torque sensing devices is opening new avenues for exploration and applications of the EdH effect. The scale-up of resonance frequencies with continued miniaturization of mechanical torque sensing resonators enhances EdH torques, which increase linearly with drive frequency, relative to frequency-independent magnetic cross-product torques. Previously, miniaturized EdH experiments have been performed at the microscale using mechanical modes in the audio frequency range (13 kHz) [2]. The present work brings the measurements to radio frequencies. 

Single-crystal Yttrium Iron Garnet (YIG) disks with magnetic vortex ground states are mounted on nano-scale mechanical resonators with a torsional resonance mode close to 3 MHz. For DC bias fields below about 200 A/m the maximum cross-product torques remain smaller than the EdH torques [3]; no control of the field geometry to null cross-product torques is required. Quadrature lock-in measurements allow cross-product and EdH torque signals to be recorded simultaneously, owing to a 90$^{\circ}$ relative phase shift arising between the driving torques, and referenced to the phase of the driving field. The simultaneous measurement scheme enables determination of the magnetomechanical ratio, $g\prime$, without requiring separate experimental inputs. Results from measurements around the full vortex hysteresis loop, and comparisons with micromagnetic simulations of cross-product and EdH torques, also will be discussed.

[1] A. Einstein and W.J. de Haas, Proceedings - KNAW **18**, 696 (1915).

[2] T.M. Wallis, J. Moreland, and P. Kabos, Appl. Phys. Lett. **89**, 122502 (2006)

[3] K. Mori, M.G. Dunsmore, J.E. Losby, D.M. Jenson, M. Belov, and M.R. Freeman, Phys. Rev. B **102**, 054415 (2020)

The Einstein-de Haas Effect in Yttrium Iron Garnet at 3 MHz

The classical Einstein-de Haas (EdH) effect [1] is a AC mechanical torque arising from a time rate of change of net magnetization, and represents the intrinsic relationship between magnetism and mechanical angular momentum. Nanofabrication of torque sensing devices is opening new avenues for exploration and applications of the EdH effect. The scale-up of mechanical resonance frequencies with continued miniaturization enhances EdH torques, which increase linearly with drive frequency, relative to frequency-independent magnetic cross-product torques. Previously, miniaturized EdH experiments have been performed at the microscale using mechanical modes in the audio frequency range (13 kHz). The present work brings the measurements to radio frequencies. Single-crystal Yttrium Iron Garnet (YIG) disks with magnetic vortex ground states are mounted on nanomechanical resonators having fundamental torsional modes close to 3 MHz. For DC bias fields below about 200 A/m the maximum cross-product torques, historically an important source of systematic error in EdH experiments, remain smaller than the EdH torques [3]; no control of the field geometry to null cross-product torques is required. Quadrature lock-in measurements allow cross-product and EdH torque signals to be recorded simultaneously, owing to a 90○ relative phase shift arising between the driving torques, and referenced to the phase of the driving field. The simultaneous measurement scheme enables determination of the magnetomechanical ratio, g′, without requiring separate experimental inputs. Results from measurements around the full vortex hysteresis loop, and comparisons with micromagnetic simulations of cross-product and EdH torques, also will be presented and discussed.References: [1] A. Einstein and W.J. de Haas, Proceedings - KNAW 18, 696 (1915). [2] T.M. Wallis, J. Moreland, and P. Kabos, Appl. Phys. Lett. 89, 122502 (2006) [3] K. Mori, M.G. Dunsmore, and M.R. Freeman, arXiv:2005.08406 [cond-mat.mes-hall] (2020) 

**Session chair:** Lise-Marie Lacroix, Université de Toulouse



EOB - Magnetic Nanostructures and Exchange Bias

technical paper

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

Please register for the Joint MMM-Intermag conference to join the event.

2022 Joint MMM-INTERMAG

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

*Sponsored by:*

![](https://assets.underline.io/uploads/markdown_image/1/image/473d3568092d9e55a528f404e82ee53c.png)
 



**Session Chair: ** Bruce Gaulin

W-POS-G #57-74 Poster session (Mag.North) / Session d'affiches (Nord mag.)

poster

**WELCOME TO THE 2021 CAP VIRTUAL CONGRESS UNDERLINE PLATFORM**

The CAP staff and our organizing and program committees are pleased to welcome you to our 2021 Congress filled with plenary talks, technical sessions/talks, student presentations and competition sessions, workshops, and several symposia offered by the CAP divisions and its partners.  

You will also have opportunities to network with other delegates through the Gathertown platform accessed by selecting the lounge or posters button on the left.

Registered delegates should use the schedule button to call up the details of the session/event they wish to attend.  Each sessions includes a link to access the online platform where the event is taking place, either within Underline or through other Congress-related Zoom meetings.  

Invited speaker talks are identified with an (I), and student competitors include a (G*) or (U*) to identify graduate or undergraduate presenters.

Please take the time to check out the information about our sponsors and exhibitors, request further information, or leave a note of thanks for their support.

General information about the Congress can be found on the CAP website Congress pages at https://www.cap.ca/congress/2021.

Looking for a specific talk?   A full searchable list is available on our Indico Congress site at https://indico.cern.ch/event/985448/contributions/

We look forward to sharing this exciting week with you!


CAP Virtual Congress 2021

N5: Novel Sensors II

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!


Michael Dunsmore

3

2

SHORT BIO

Presentations

Three-axis torque investigation of exchange bias in a micromagnetic disk

The Einstein-de Haas Effect in Yttrium Iron Garnet at 3 MHz

The Einstein-de Haas Effect in Yttrium Iron Garnet at 3 MHz

Stay up to date with the latest Underline news!

PRESENTATIONS

CONFERENCES

COMPANY

RESOURCES