Spin accumulation, which is created by an electrical current flowing in a nanomagnet, affects the strength of spin-orbit interaction (SO) and anisotropy field Hani in a nanomagnet. The reduction of Hani and SO by the current may cause a magnetization reversal. As a result, the data, which is encoded into the current, is memorized by means of two equilibrium magnetization directions of the nanomagnet. Recently, we have developed a high-precision measurement method of Hani and coefficient of spin-orbit interaction kso [1]. kso is a numerical parameter characterizing the SO strength.
Figure 1 shows kso vs. Hani measured in FeCoB nanomagnets.The SO strength is larger in nanomagnet, which contains several ferromagnetic layers (shown by stars) in comparison with nanomagnets containing only one ferromagnetic layer(shown by triangles). It means that the SO strength depends on the number of interfaces. The SO strength increases with an increase of the number of FeB layers up to 5 FeB layers. Further increase of the number of FeB layers causes a decrease of kso due to accumulated interface roughness.
Figure 2 compares current dependency of Hani for a single and multilayer nanomagnet. In the multilayer nanomagnet with a strong SO, the reduction of Hani is large of about 25 % and is nearly independent of current polarity. In contrast, in the single- layer nanomagnet with a weak SO, Hani changes almost linearly with the current only with a small symmetrical contribution due to heating, but the change is small of about 6%. Even such a small change of Hani is sufficient for magnetization reversal, when the conditions for the parametric resonance are met [2,3]. 
**References** [1] https://www.youtube.com/watch?v=LmvYN5hG-90
[2] V. Zayets, arXiv:2104.13008 (2021).
[3] V. Zayets, IOA-07, MMM (2021)
 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/9401aaab425da8f4340dec5295e11065.png)

Peculiarities of measured dependencies of strength of spin orbit interaction and anisotropy field on current density in FeCoB nanomagnet

VCMA effect describes the fact that in a capacitor, in which one of electrodes is made of a thin ferromagnetic metal, the magnetic properties of the ferromagnetic metal changes, when a voltage is applied to the capacitor[1]. Inside a metal the electrical field is screened by free electrons and cannot penetrate deep inside the metal. As a result, the voltage, which is applied to the capacitor dielectric (gate), may penetrate into and affect only the few uppermost atomic layers of the metal near the gate. However, the change of magnetic properties of the uppermost layer by the gate voltage affects the magnetic properties of the whole film. This can be only the case if the interfacial perpendicular magnetic anisotropy (PMA) is affected by the gate voltage [2]. The strength of PMA is characterized by the anisotropy field Hani and proportional to the strength of spin-orbit interaction, demagnetization field and magnetization of nanomagnet.
Fig.1 shows the measured Hani and coefficient of spin-orbit interaction kso in FeCoB nanomagnet under a different gate voltage. kso defies the strength of the spin-orbit interaction[3]. Hani decreases and kso increases under an increase of gate voltage. It is unexpected because Hani is linearly proportional to kso [3] and should increase when kso increases. It means that even though the strength of the spin-orbit interaction is affected by the gate voltage, but additionally to kso there is another voltage- dependent parameter, which defines the voltage dependence of Hani. The intrinsic field in nanomagnet or demagnetization field might be such a parameter.
Fig.2 shows measured Hani and kso of different nanomagnet of different wafers. The same tendency exists in all measured nanomagnets. 
**References** [1] Y. Shiota, T. Nozaki, F. Bonell, S. Murakami, T. Shinjo, Y. Suzuki, Nat. Mater. 11 (2012) 39–43.
[2] V. Zayets, T. Nozaki, H.Saito, A. Fukushima, S.Yuasa, arXiv:1812.07077 ( 2018).
[3] V.Zayets, IOA-07, MMM 2021. 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/a6361675ad1be5f1cde60655b785b878.png)

Unexpected opposite dependencies of anisotropy field and strength of spin orbit interaction on gate voltage measured in FeCoB nanomagnet

A new mechanism of recording for a MRAM cell, which is based on a parametric resonance, has been proposed [1] and experimentally studied. The parametric mechanism requires a substantially smaller spin torque for the magnetization reversal due to the resonance nature of this recording mechanism and, therefore, it can be a solution for further reduction of the recording energy for the MRAM operation. Two parametric mechanisms for the magnetization reversal are proposed, studied and experimentally evaluated. The first mechanism is due to a modulation of the magnetic field of the Spin- Orbit Torque. The second mechanism is due to modulation of the anisotropy field. For both mechanisms, a parametric torque is created by a RF modulated current, which resonantly enhances the magnetization precession until a magnetization reversal. Additionally, a parametric mechanism for magnetization reversal by a DC current is proposed and studied. This parametric mechanism may occur in a magneto-resistive structure, in which a magnetization precession modulates an electrical current. It results in a positive feedback loop, in which a magnetization precession creates a torque, which more enhances the precession.

![](https://assets.underline.io/uploads/markdown_image/1/image/542c9b5a32048ecc7a06babee370e4ca.jpg)

![](https://assets.underline.io/uploads/markdown_image/1/image/256f37dab48ea38e1c2550f583dbc4f5.jpg)

Experimental evolution of two parametric mechanisms of magnetization reversal in FeCoB nanomagnet.

Experimental evolution of two parametric mechanisms of magnetization reversal in FeCoB nanomagnet.

An electrical current flowing through a nanomagnet can create an accumulation of spin- polarized electrons at nanomagnet boundaries. The magnetic field H(SA), which is originated by the accumulated spins, causes a torque, which may reverse the magnetization direction of the nanomagnet. This effect is called the Spin-orbit torque (SOT). The effect is used as a writing mechanism in magnetic Random Assess Memory (MRAM). We report high-precision measurements of H(SA) in a FeCoB nanomagnet. A conventional measurement method of SOT is the method of the second harmonic1-3, in which the current in the nanomagnet is modulated at a low frequency (~ 1 kHz) and the second harmonic of the Hall voltage is measured by the lock-in technique. In this method the second harmonic is generated due to the modulation of the magnetization direction by the current. The electrical current creates the spin accumulation due to the Spin Hall effect. The magnetic field H(SA) of the spin accumulation turns the magnetization direction from its easy axis. The Hall voltage is linearly proportional to the current and to the perpendicular component of the magnetization and they both are modulated. The frequency beating creates the second harmonic, which is proportional to the induced magnetic field H(SA) and therefore to the spin accumulation. This measurement method of H(SA) is indirect and contains several non-linear contributions, which makes the result interpretation difficult. For the same reason, it is difficult to identify a systematical error within this measurement method; the method suffers from a poor measurement precision and a poor reproducibility. The abstract describes a new method to measure magnetic field H(SA), which is induced by the spin accumulation in a nanomagnet. The proposed measurement is a direct measurement of H(SA). The merits of proposed method are a high precision (~1 Oe), a high- reproducibility and repeatability. A measurement of a magnetic field, which is induced by a tiny nanomagnet, is a challenging task. Additional measurement challenge is that the measured magnetic field H(SA) is very small. In the proposed method, the magnetic field H(SA) is measured by scanning external magnetic field Hext perpendicularly to the magnetization direction and a DC measurement of the Hall voltage. The H(SA) is evaluated from the symmetry of the scan with respect to the reversal of the Hext direction. The measurement of H(SA) in a nanomagnet is based on the fact that the nanomagnet magnetization is turned towards the H(SA) or towards any other magnetic field applied perpendicularly to the magnetization easy axis. The turning angle is symmetrical with respect to a reversal of direction of the applied magnetic field. The H(SA) is small (about of a few Oe) and therefore the magnetization turning angle is small (~0.10) and difficult to measure. In the proposed method, a larger external magnetic field H is applied and scanned from negative to positive polarity. The H(SA) slightly shifts symmetry point of the scan from the point H=0. The fitting of the positive part of the scan to the negative part gives H(SA) with a high precision. The magnetic field H(SA) induced by the spin accumulation is measured in a FeCoB (thickness is 1.1 nm) fabricated on top of a Ta (thickness is 2.5 nm) nanowire contacted by a pair of Hall probes. The magnetization of the nanomagnet is perpendicular-to-plane. About 100 nanomagnets, which sizes vary between 50 x 50 nm to 3000 x 3000 nm, were measured. The external in-plane magnetic field is scanned either along or perpendicular to the current for an individual measurement of each component of H(SA). Additionally, a perpendicular- to- plane magnetic field Hz is applied in order to verify the dependency of the H(SA) on the Perpendicular Magnetic Anisotropy (PMA)4. Figure 1 shows measured H(SA) as a function of Hz and the current density for a 3000 x 3000 nm nanomagnet. The H(SA) depends substantially on both Hz and current density and both dependencies are related to each other. The component of H(SA), which is induced by the current, is always perpendicular to the component of H(SA), which is induced by perpendicular magnetic field Hz. Since Hz modulates the PMA strength4, the observed dependence implies that the current- induced H(SA) is substantially influenced by the PMA effect. It was suggested2 that the second harmonic method measures two different types of torques. The field-like (FL) torque is measured, when the magnetization is inclined along the current. The damp-like (DL) torque is measured, when the magnetization is inclined perpendicularly to the current. The suggestion was based on the symmetry of H(SA) with respect to the magnetization reversal. We have observed the same symmetry (Fig.1). However, our measurements can be explained more clearly by assuming that instead of two independent objects (FL and DL torques) there is only one independent object: the magnetic field H(SA), which is monotonically changing its direction and magnitude influenced by Hz and current. There are clear tendencies for observed direction and magnitude of H(SA). The direction of H(SA) is about 450 with respect to current for a larger nanomagnet (size &gt; 800 nm) and nearly parallel to current for a smaller nanomagnet.

**References:**

[1] U. H. Pi et al., APL Vol. 97, p.162507 (2010). [2] K. Garello et al., Nat. Nanotechnol. Vol. 8, p. 587 (2013). [3] J. Kim et al., Nat. Mater. Vol. 12, p. 240 (2013). [4] V.Zayets MMM 2020, N4-03.

**Images:**

![](https://assets.underline.io/uploads/markdown_image/1/image/32dbb01cfb837cdeba6ee0aea46dc68f.jpg)
Fig.1 Measured in-plane magnetic field H(SA) induced by the spin accumulation as a function of a perpendicular-to- plane magnetic field and current density in a FeCoB nanomagnet. Measured component of H(SA) (a) along current (b) perpendicular to current.

![](https://assets.underline.io/uploads/markdown_image/1/image/8a8ba41cbd2d7f0f085194b85ece729e.jpg)

 High-precision measurement method of magnetic field induced by spin- accumulated electrons in FeCoB nanomagnet

A FeCoB nanomagnet with perpendicular magnetic anisotropy (PMA) is important as a storage element for Magnetic Random Access memory (MRAM), because of their single-domain magnetic state and a high-thermal stability. In order to achieve a required high- performance of MRAM, both the enhancement of the PMA and a high-controllability of PMA are required. A parameter, which characterizes the PMA strength in a nanomagnet, is the anisotropy field Hanis. The Hanis is the magnetic field, which is applied in-plane and therefore perpendicularly to the easy axis of a nanomagnet and at which initially-perpendicular magnetization turns completely to the in-plane direction. A half of product of Hanis and nanomagnet magnetization is a common estimate of the PMA energy [1]. We measure the Hanis as a function of a perpendicularly- applied external magnetic field Hz using a Hall setup. In-plane magnetic field Hx and Hz were applied simultaneously. Under a fixed Hz, the Hx was scanned. Measured in-plane component of magnetization Mx changes linearly with respect to Hx (at least in region -0.7 Hanis < Hx <0.7 Hanis). From the slope of the measured linear dependence, the Hanis is evaluated. Figure 1 shows the measured Hanis vs Hz for a magnetically-softer FeB nanomagnet (Hc=70 Oe) and magnetically-harder FeCoB nanomagnet (Hc=560 Oe). In both nanomagnets, the dependence becomes linear at Hz >3 kG as it is predicted theoretically. From the slop of the linear dependence the strength of the Spin-Orbit interaction at nanomagnet interface is estimated. The dependence at smaller Hz gives an estimate of the intrinsic magnetic field, which always exists along nanomagnet magnetization, and the demagnetization field.References: [1] M.T. Johnson, P.J.H. Bloemen, F.J.A. Den Broeder, and J.J. De Vries, Reports Prog. Phys. Vol. 59, p.1409 (1996).

Measurement of anisotropy field under external perpendicular magnetic field in FeCoB and FeB nanomagnets. Study of PMA features in a nanomagnet

We measured the Hall effect (HE) in a ferromagnetic nanomagnet with a strong perpendicular magnetic anisotropy (PMA), in which the local magnetic moments are very stable and well- aligned along the easy axis of the nanomagnet. The adopted mechanisms of HE predict linear plus a constant dependence on the external field originating from the ordinary and anomalous Hall effects, respectively. Our measurement revealed an extra non- linear contribution indicating an additional contribution to HE, which was suggested to be the Inverse Spin Hall effect (ISHE). The ISHE describes the fact that an electrical current is created perpendicularly to the flow of the spin- polarized current. The ISHE requires existence of the spin-polarized electrons. In a ferromagnetic metal the electron gas is spin- polarized even in equilibrium and any electrical current in a ferromagnetic metal is spin- polarized. As a result, any electrical current in a ferromagnetic metal must always experience the ISHE and there must be a flow of the Hall current perpendicularly to the bias current. There are several methods to change the number of spin- polarized electron in a ferromagnetic metal and therefore the magnitude of the ISHE. E.g. the spin polarization can arise due to the influence of an external magnetic field, the mechanism considered by Landau and Lifshitz a long time ago[1]. The Hall angle αHE can be presented as αHE = αOHE H+ αAHE + αISHE PS(H) where the non-linear dependence of spin polarization PS on magnetic field is calculated as[2] PS(H)=(PS,0+H/HS)/(1+H/HS) where PS,0 is the spin polarization at H=0. HS is the scaling magnetic field. Figure 1 shows that the fit of the experimental data with the above relation is excellent proving the importance of the ISHE contribution to the HE in a ferromagnetic metal.References: [1] L. D. Landau and E. M. Lifshitz, Phys. Z. Sowjetunion. Vol. 8, p.153 (1935). [2] V. Zayets, J. Magn. Magn. Mater. Vol. 356, p. 52 (2014).

Study of magnetic field dependence of Hall effect in FeB and FeCoB nanomagnets. An evidence of contribution of Inverse Spin Hall effect

EOE: Spin-Orbitronics I

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>

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.

**Please click on the poster to see the abstract or leave your comment to the author.** 
**Session Chair:** Markus Gößler, *Chemnitz University of Technology*

CPA: Magnetoelectronic Materials and Phenomena

poster

**Session chairs:** Chris Rea, Seagate and Wei-Heng Hsu, Seagate


IOA - Magnetic Recording Technology I

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

*Session Chair: Tao Wang, Huazhong University of Science and Technology*

These on-demand presentations are available to view at your leisure.

CB: Spin Injection and Spin Transfer Torques

INTERMAG 2021 Welcome Video



	
<figure class="video_container">
 <iframe src="https://screencast-o-matic.com/player/crflqFVnUpZ?v=6&ff=1&title=0&controls=1" width=640 height=360 frameborder="0" allowfullscreen="true"> </iframe>
</figure>

Want to buy a ticket? 

Register for INTERMAG 2021 here

[![](https://assets.underline.io/uploads/markdown_image/1/image/17ce76e7960db633258024eef8d6da7f.png)](https://intermag.org/register)

Got your ticket, but still can’t access the event?

Contact us and our team will look into it.

INTERMAG 2021

N4: Magnetic Tunnel Junction and Related Effects, Voltage Controlled Magnetism

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!


Vadym Zayets

6

19

SHORT BIO

Presentations

Peculiarities of measured dependencies of strength of spin orbit interaction and anisotropy field on current density in FeCoB nanomagnet

Unexpected opposite dependencies of anisotropy field and strength of spin orbit interaction on gate voltage measured in FeCoB nanomagnet

Experimental evolution of two parametric mechanisms of magnetization reversal in FeCoB nanomagnet.

High-precision measurement method of magnetic field induced by spin- accumulated electrons in FeCoB nanomagnet

Measurement of anisotropy field under external perpendicular magnetic field in FeCoB and FeB nanomagnets. Study of PMA features in a nanomagnet

Study of magnetic field dependence of Hall effect in FeB and FeCoB nanomagnets. An evidence of contribution of Inverse Spin Hall effect

Stay up to date with the latest Underline news!

PRESENTATIONS

CONFERENCES

COMPANY

RESOURCES