United States

Magneto-ionics (MI) provides a nonvolatile EF modulation of magnetism through the migration of ions toward/away from the magnetic interfaces that allows for low-power spintronics devices. However, the ionic mechanism involved still needs to be explored, as key properties such as reversibility have been shown to strongly depend on the chemical composition and oxidation level of the ferromagnet (FM)/oxide interface, (1–3), and on the degree of crystallinity of the system (4). We have recently shown that the gate-voltage driven degree of oxidation at the FM/oxide interface in Ta/Co20Fe60B20/HfO2 defines two MI regimes: (I) underoxidized to optimally oxidized, and (II) optimally oxidized to overoxidized, accompanied by a change in the magnetization easy axis from in-plane (IP) to out-of-plane (OOP) in regime I and from OOP to IP in regime II (3). Only regime II showed reversibility, which was linked to the different binding strength of the oxygen species in regimes I and II.
In this work, we present the MI behavior in Pt/Co60Fe20B20/HfO2, where also two MI regimes have been identified. In this system, both regime I and II are reversible, but the stability of the nonvolatile magnetic states was found to be significantly different in regime I and II. Magnetic states in regime I was found to be highly stable, with no significant loss of remanence in the hysteresis loops over several weeks after applying the gate voltage. In this regime, a significant variation of the Dzyaloshinskii-Moriya interaction was also observed. In contrast, the magnetic states in regime II (between OOP and IP) were found to evolve with time back to the OOP state within one day after applying the gate voltage. Interestingly, only the final overoxidized IP state is fully stable in regime II.
This disparity in the stability of the MI states in regimes I and II could be attributed to differences in the gate-voltage driven chemical reactions and ionic transport, where also the composition of CoFeB may play an important role. Our results show the importance of studying the link between the ionic mechanisms and the MI state stability, in view of practical applications in spintronics.&lt;br&gt;

**References:**&lt;br&gt;
(1) L. Herrera Diez, Y. T. Liu, M. Belmeguenai, et al., Physical Review Applied, 12, 034005 (2019);&lt;br&gt;
(2) A. Fassatoui, L. Ranno, S. Pizzini, et al., Physical Review Applied, 14, 064041 (2020),&lt;br&gt; 
(3) R. Pachat, D. Ourdani, L. Herrera Diez. et al., Physical Review Applied, 15, 064055 (2021),&lt;br&gt;
(4) R. Pachat, D. Ourdani, L. Herrera Diez, et al., Adv. Mat. Inter., Accepted (2022)&lt;br&gt;

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/ea145b4e40c9304eb75f27a8883b090a.png)

MMM 2022

Stability of under/over oxidized magneto ionic states in Pt/Co60Fe20B20/HfO2

Magneto-ionics (MI) provides a nonvolatile EF modulation of magnetism through the migration of ions toward/away from the magnetic interfaces that allows for low-power spintronics devices. However, the ionic mechanism involved still needs to be explored, as key properties such as reversibility have been shown to strongly depend on the chemical composition and oxidation level of the ferromagnet (FM)/oxide interface, (1–3), and on the degree of crystallinity of the system (4). We have recently shown that the gate-voltage driven degree of oxidation at the FM/oxide interface in Ta/Co20Fe60B20/HfO2 defines two MI regimes: (I) underoxidized to optimally oxidized, and (II) optimally oxidized to overoxidized, accompanied by a change in the magnetization easy axis from in-plane (IP) to out-of-plane (OOP) in regime I and from OOP to IP in regime II (3). Only regime II showed reversibility, which was linked to the different binding strength of the oxygen species in regimes I and II.
In this work, we present the MI behavior in Pt/Co60Fe20B20/HfO2, where also two MI regimes have been identified. In this system, both regime I and II are reversible, but the stability of the nonvolatile magnetic states was found to be significantly different in regime I and II. Magnetic states in regime I was found to be highly stable, with no significant loss of remanence in the hysteresis loops over several weeks after applying the gate voltage. In this regime, a significant variation of the Dzyaloshinskii-Moriya interaction was also observed. In contrast, the magnetic states in regime II (between OOP and IP) were found to evolve with time back to the OOP state within one day after applying the gate voltage. Interestingly, only the final overoxidized IP state is fully stable in regime II.
This disparity in the stability of the MI states in regimes I and II could be attributed to differences in the gate-voltage driven chemical reactions and ionic transport, where also the composition of CoFeB may play an important role. Our results show the importance of studying the link between the ionic mechanisms and the MI state stability, in view of practical applications in spintronics. 

**References:** 
(1) L. Herrera Diez, Y. T. Liu, M. Belmeguenai, et al., Physical Review Applied, 12, 034005 (2019); 
(2) A. Fassatoui, L. Ranno, S. Pizzini, et al., Physical Review Applied, 14, 064041 (2020), 
(3) R. Pachat, D. Ourdani, L. Herrera Diez. et al., Physical Review Applied, 15, 064055 (2021), 
(4) R. Pachat, D. Ourdani, L. Herrera Diez, et al., Adv. Mat. Inter., Accepted (2022) 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/ea145b4e40c9304eb75f27a8883b090a.png)

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.

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

Neuromorphic computing is a particularly exciting application of spintronics, able to exploit its rich physics to achieve low-power-consumption computation inspired by the brain. Designing neuromorphic systems requires simulating the response of spintronic devices to multiple types of inputs over long time periods. Currently, the dominant approach to predicting the complex behavior of spintronic devices is micromagnetic simulation. This technique, however, requires very long simulation times, easily reaching weeks in time-dependent experiments or in micrometer-scale devices. In this work, we take an alternative road by adopting a deep learning technique, Neural Ordinary Differential Equations (ODEs), to model spintronic devices and develop spintronic systems. We show that Neural ODEs, trained on a minimal amount of data, can predict the behavior of spintronic devices with high accuracy and an extremely efficient simulation time, compared to micromagnetic simulations. For this purpose, we re-frame the formalism of Neural Ordinary Differential Equations (ODEs) [1] to the constraints of spintronics: few measured outputs, multiple inputs and internal parameters (Fig. 1). We demonstrate with Neural ODEs an acceleration factor over 200 compared to micromagnetic simulations for a neuromorphic system -- a reservoir computer made of magnetic skyrmions (20 minutes compared to three days). We also demonstrate that this state-of-the-art deep learning technique for time series modeling can be applied to model an experimental neuromorphic experiment [2], in which spin-torque nano-oscillators are used as reservoir computers to achieve a spoken digit recognition task (Fig. 2). Neural ODEs can therefore constitute a disruptive tool for developing spintronic applications in complement to micromagnetic simulations, which are time-consuming and cannot fit experiments when noise or imperfections are present [3].

Building spintronics neuromorphic systems with Neural Ordinary Differential Equations

Neuromorphic systems are of great interest for modeling and solving complex problems, offering an alternative to conventional deterministic computers1. They generally aim to emulate the functionality and structure of the human brain and thus require many independent true random noise signal sources. In recent years, the stochasticity of spin-transfer-torque switching of magnetic tunnel junctions (MTJs) has gained interest for such applications. Focusing on in-plane MTJs with low energy barriers, the devices investigated thus far have fast thermally driven random fluctuations2,3. However, they are highly susceptible to small changes in temperature and device parameters. Here we show the room-temperature operation of medium energy barrier (Δ=394) perpendicularly magnetized MTJs (pMTJs) in the ballistic switching limit (ns duration pulses) and discuss why their operation is much less sensitive to temperature and material parameters. In the ballistic limit the resulting junction state is random mainly because of the thermal distribution of the initial magnetization state. We denote this a stochastic magnetic actuated random transducer (SMART) device because the pulse activates the junction to generate a random bit stream, much like a coin flip. In fact, we analyze the stochastic nature of our SMART devices by comparing their statistics to that expected of Bernoulli trials (see Figs.1 and 2). We also test our bit stream with the NIST statistical test suite for random number generators which investigates their suitability for cryptography. We find that by whitening the bit stream with only one XOR operation, we pass all NIST tests. Our results demonstrate that medium energy barrier pMTJs are very promising candidates for true random number generation due to their easily controllable characteristics, while being robust towards environmental changes and material parameter variations. 
**References** 1Schuman, C. D. et al., arXiv:1705.06963.
2Vodenicarevic, D. et al., Physical Review Applied Vol. 8, 054045 (2017).
3Safranski, C. et al., Nano Letters Vol. 21, 2040–2045 (2021).
4Rehm, L. et al., Physical Review Applied Vol. 15, 034088 (2021).
 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/8e61c8ec8ec8f3646e028cfc282d7a37.png)

Stochastic Magnetic Actuated Random Transducer Devices based on Perpendicular Magnetic Tunnel Junctions

Dzyaloshinskii–Moriya interaction (DMI) induced ferromagnetic (FM) skyrmions in chiral magnets have been reported last decade1,2. On the other hand, chiral antiferromagnet could be a great candidate to host antiferromagnetic (AFM) skyrmions, which have not been studied yet. The emergence of room-temperature FM skyrmions has been reported in the field β-Mn type Fe2-xPdxMo3N epitaxial thin films1. We report Pd doping effect on magnetic and transport properties of a series of chiral antiferromagnetic filled β-Mn type Co2-xPdxMo3N (CPMN) thin films.
A series of CPMN (x = 0 ~ 1.61) thin films were fabricated on c-plane sapphire substrates. Figure 1(a) shows the 2θ/θ scan XRD pattern of a CPMN thin film with x = 1.01, indicating that CPMN films grown epitaxially in the (110) direction, as in case of Fe2-xPdxMo3N/Al2O31. Figure 1(b) shows the x dependence of c0 indicating the on-site doping of Pd. Figure 1(c) shows the M-T curve of a CPMN film with x = 1.01, where two anomalies are identified, which appeared in all CPMN films. The high-temperature anomaly could be related to the Néel temperature TN, as in case of bulk Co2Mo3N3. The magnetization MS at 200 K is 3×10-2 μB/f.u., which is 70 times smaller than that of ferromagnetic Fe2-xPdxMo3N films1, which suggests that the high-temperature magnetic phase is a canted antiferromagnetic (AFM) phase. The low-temperature anomaly can be ascribed to the spin reorientation, at which temperature (TSR) the transition between AFM phase and spiral phase occurs as reported in chiral antiferromagnetic K2V3O84. The low-temperature spiral phase is also revealed by topological Hall effect (THE) at 4 K (Fig. 1(d)). The vanishing THE in canted AFM phase at 200 K (Fig. 1(d)) might be due to the AFM skyrmions. We will report the details of magnetic and transport properties of CPMN system. 
**References** [1] B. W. Qiang et al., Appl. Phys. Lett. 117, 142401 (2020).
[2] R. Saha et al., Nat. Commun. 10, 5305 (2019).
[3] W. Li et al. Phys. Rev. B 93, 060409(R) (2016).
[4] M. D. Lumsden et al., Phys. Rev. Lett. 86, 159 (2001)
 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/91ed243d485e05d7f5a1cbe97ca6d678.png)

Magnetic and Transport Properties of Chiral Antiferromagnetic Co2 xPdxMo3N Thin Films

Spin-orbit interaction in metals and its ability to generate spin-current has been the hallmark of spintronics in the last decade. Beyond its fundamental interest as a source of spin-current, the manipulation of magnetization via transfer of the spin angular momentum has proven to be energy efficient for spin-based memory (e.g. SOT-MRAM) and also neuromorphic devices (e.g. using spin Hall nano-oscillators). Therein, charge to spin conversion is believed to be governed essentially by two main mechanisms, spin Hall effect in the bulk of heavy-metals and Rashba effect at interfaces [1], the latter being often considered negligible in all-metallic interfaces. However, in the case of atomically thin metallic layers, the underlying SOT physical mechanisms at play have not been experimentally fully tackled. 
In this study, we examine the impact of the insertion of a light element interface on the nature of the SOT as well as its efficiency in terms of damping-like (HDL) and field-like (HFL) effective fields in ultrathin ferromagnets. Importantly, we observe unexpectedly large HFL/HDL ratio (∼2.5) upon inserting a 1.4 nm thin Al layer in Pt|Co|Al|Pt as compared to Cu instead of Al as shown in Fig. 1. From our modeling (dotted lines in Fig.1), these experimental results strongly evidence the presence of a large interfacial Rashba effect at Co|Al interface producing giant HFL. The occurrence of such enhanced torques from an interfacial origin is further validated by reducing the contribution from SHE in the bottom Pt layer as well as by demonstrating current-induced magnetization reversal at reduced current. We believe that our results are important from the application point of view as they provide a clear route for reaching ultimate spin-torque efficiency for the associated devices[2]. 
**Acknowledgement:** DARPA TEE (MIPR no. HR0011831554), the Horizon2020 Framework Program of the European Commission under FET-Proactive Grant agreement No. 824123 (SKYTOP) and the the Agence Nationale de la Recherche, France, No. ANR-17-CE24-0025 (TOPSKY). 
**References:** [1] Manchon, A. et al., Rev. Mod. Phys. 91, (2019). 
[2] Krishnia S. et al., arXiv : 2205.08486. 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/d8fd135b8e9157bc0dc4a5f819d2811b.png) 
Co thickness (tCo) dependence of (a) DL-SOT field and (b) FL-like SOT fields in Pt8|Co (tCo)|Al1.4|Pt3 (red ) and Pt8|Co (tCo)|Cu1.4|Pt3 (blue ) samples (c) ζ = HFL/HDL as a function of tCo.

Large interfacial Rashba interaction and giant spin orbit torque in atomically thin metallic multilayers

Realization of novel topological phases in magnonic band structures represents a new opportunity for the development of low-dissipation magnonics [1-5]. The previous proposals require materials with either special crystal symmetries [2-3] or artificially modulated structures that demand advanced nanofabrication techniques [4-5], both of which bring in difficulties for experimental realization. In this work, we theoretically study the magnonic band structure of antiparallelly aligned magnetic multilayers (Fig. 1), and reveal their field-tunable topological phases [1]. We show that the long-range dipolar interaction between propagating magnons is chiral in nature, whose strength depends on the wave vector direction and therefore breaks time-reversal symmetry. Consequently, the dipolar interaction plays a role like spin-orbit coupling in electronic systems and generates bulk bands with non-zero Chern integers and ultra-localized magnonic surface states that carry chiral spin currents (Fig. 1). Through an external magnetic field, the topological phases can be switched, which therefore provides a tunable for transferring spin angular momenta in this synthetic antiparallelly aligned heterostructure. Besides analytical study, we also carry out micromagnetic simulations on the simplest multilayer system â€“ YIG/Py bilayers using MuMax3 [6]. The magnonic band structure with a degeneration point only in one half of the reciprocal space and the unidirectional propagation of spin waves (Fig. 2) both validate our analytical results. Our study provides an easy-to-implement system for realizing topologically protected magnonic surface states and low-dissipation spin transport in a tunable manner, which is expected to benefit various areas of modern spintronics and magnonics.

Tunable Magnonic Chern Bands and Chiral Spin Currents in Magnetic Multilayers

The direct interference of short wavelength spin waves in continuous layers is bringing new opportunities for efficient signal processing [1-2]. Several pionneer works established the possibility to shape the propagation of spin waves in ferromagnetic thin films using concepts borrowed from optics [3-5]. Along these ideas, we demonstrated that the focused emission of spin waves beams in ferromagnetic thin films from constricted coplanar waveguide follows directly the near-field interference pattern of the constriction geometry [6]. In this communication, we investigate the interference patterns of spin waves excited by curvilinear shaped antennas, which produce either a concentrating or a diffusing effect. Namely, we focused our study on two different types of demonstrators: (i) a spin wave â€œconcentratorâ€ as shown in Fig. 1, and (ii) the equivalent of a â€œYoung double-slitâ€ experiment for spin waves shown in Fig. 2. Firstly, we will present a near-field interference model that can be readily implemented for all spin wave modes and any arbitrary shape of antenna [7]. We show the validity and efficiency of our approach by comparing the near-field diffraction patterns obtained with our model and the corresponding MuMax3 micromagnetic simulations for a wide scope of geometries. Secondly, we present series of propagating spin wave spectroscopy done on 30nm YIG films and a 20nm Ni80Fe20 film magnetized out-of-plane, allowing for a discrete mapping of the spin wave intensity with a spatial resolution of about 1Âµm. We show that the transmission signals S21 measured at different locations follow very closely the simulated interference patterns for all the demonstrators, thus paving the way for future prototypes of magnon interferometric devices. This work was supported by the French ANR project â€œMagFuncâ€, and the DÃ©partement du FinistÃ¨re through the project â€œSOSMAGâ€.

Spin Wave Diffraction in Curvilinear Antennas

Magnetic Tunnel Junctions (MTJ) are one of the major building blocks of spintronics, used in random access memory designs due to non-volatility, endurance and fast
switching. Regardless of the choice of writing scheme, e.g Spin-Transfer Torque (STT)[1] or Spin-Orbit Torque (SOT)[2], we need to tailor the intrinsic properties of the switchable
magnet (the Free Layer) in order to ensure a high retention time of the magnetization state, representing a trade off with respect to the switching energy, i.e the more retention, the more
energy required to operate the device.
To overcome the dilemma and enable MTJs with high retention and low writing energy, a Hybrid Free Layer (HFL) concept has been previously proposed by integrating a Synthetic
Antiferromagnet (SAF) stack into the widely used CoFeB/MgO Free Layer stack[3]. This HFL has two intrinsic interlayer couplings tailored by a SAF and SFM (synthetic ferromagnet)
spacers (Fig. 1). The SAF spacer reduces the stray field and gives an exchange coupling torque from the motion of either layer II or III, leading to faster overall motion of the stack. The
SFM spacer allows for flexibility in the choice of SAF design, as it couples the layer I directly to layer II, but also decouples the crystallization of the Tunneling Barrier interface from layer
II, preventing lattice mismatching effects and bad electronic band conditions in a wide range of materials[4].
This work explores this design focusing on compensation of ground states (where the stack adds up to no field). We demonstrate by micromagnetics that adding a SFM to a SAF stack
impacts the energy and layer trajectories in non-trivial ways. For instance, in Fig. 2 the hysteresis loop of HFL stacks with both compensated equilibrium states and Top Major (layers I, II
generate field) show that even at compensation point we have degeneracy of states, i.e regions of external field where both low/high energy states are stable. This contrasts with SAF only
stacks where outside of compensation a behavior towards saturation is observed (Fig.2 Right). Different switching speeds can also be found by tailoring the coupling strengths. 
**References** [1] S. Sakhare et al., 2018 IEEE IEDM;
[2] S. Couet et al., 2021 Symposium on VLSI Technology, 2021, pp. 1-2.
[3] E. Raymenants et al., Nature Electronics, volume 4, pgs 392–398 (2021).
[4] Liu, E. et al., IEEE Trans. Magn. 53, 1–5 (2017). 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/f4a956e9e6108a5e1fecf8f287ec16a2.png) 

Fig.1 HFL design with top MTJ. 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/5611644821e8f98ad639563066f90281.png) 

Fig. 2 HFL (left) and SAF (right) hysteresis loops.

Micromagnetic Modelling of Multi Coupled Free Layers for Magnetic Tunnel Junction Devices

α”-Fe16N2 is a promising environmentally-friendly rare-earth-free permanent magnet material with ultra-high saturation magnetization. Recent research has demonstrated experimentally through a thermally quenching treatment using γ’ phase Fe4N as a precursor to synthesize α”-Fe16N2 in bulk format. In this research, we investigated γ’-Fe4N thin film thermal decomposition process and potential localized phase transition from fcc phase to bct phase using Molecular Dynamics (MD) simulation method. As nitrogen concentration is much higher in γ’-Fe4N (5.9 wt.%) than that in α’-Fe8N or α’’-Fe16N2 (3 wt.%), Nitrogen “depletion” process must have to occur during the thermal decomposition to form possible lower-Nitrogen content bct Fe-N solid solution. A localized “Nitrogen-rich” grain boundary lattice defect model is designed to induce Nitrogen bond forming through the recombination of nitrogen pair atoms, and therefore significantly improves local reduction of Nitrogen content in the α’-Fe4N lattice sample during thermal treatment. Modified Embedded Atom Method (MEAM) interatomic potential of Fe-N system is applied. Bond forming/breaking and local Nitrogen displacement analysis (MSD) are also performed in the thermostat-controlled heating/quenching simulation process. We use virtual XRD method and formation energy calculation to assess and detect the new material phases on the thermally-treated and energy minimized lattice sample. 
**References:** [1] Jian-Ping Wang, “Environment-friendly bulk Fe16N2 permanent magnet: Review and Prospective”, Journal of Magnetism and Magnetic Materials, 497(2020) 165962 
[2] J. Zhu, G, Guo and J.-P. Wang, "Study of γ'-F4N Annealing Process Through Molecular Dynamics Modeling", TMS 2022 151st Annual Meeting, The Minerals, Metals & Materials Series, Page 109-117, https://doi.org/10.1007/978-3-030-92381-5_11 
[3] M.H. Wetzel, M.R. Schwarz, A. Leineweber, High-pressure high-temperature study of the pressure induced decomposition of the iron nitride γ′-Fe4N, Journal of Alloys and Compounds, Volume 801, 2019, Pages 438-448

Simulation of Thermal Decomposition of γ’ Fe4N using Molecular Dynamics Method

Spin current is one of the key technologies for spintronics devices. Especially, generation of spin currents via electrical charge current has attracted a great deal of attentions from both fundamental physics and application point of views because it can manipulate magnetization vector of the ferromagnet [1]. This charge-to-spin conversion phenomena originate from spin-orbit coupling and has been widely studied in non-magnetic materials. Recently, the interest in spin conversion materials has extended to ferromagnetic materials (FMs). FMs can generate magnetization-dependent charge-to-spin conversion (MD-CSC), which is caused by the reduced mirror symmetry due to the presence of magnetization, and this MD-CSC can be used as a writing source for high-density MRAM (Fig. 1) [2]. However, the origin of this MD-CSC has not been calrified yet, for instance, whether the interfacial or bulk contribution is domoinant. In addition to this, a guideline for high spin conversion efficiency is highly required for realizing energy-efficient writing in MRAM devices. In this presentation, we systematically studied the charge-to-spin conversion in ferromagnetic material to clarify its origin [3]. Through precise measurement of spin conversion efficiency via spin-torque ferromagnetic resonance [4], we experimentally revealed that two different mechanisms, which originate from the bulk and at interface, contribute to the charge-to-spin conversion in ferromagnet. Next, we demonstrated a guideline to enhance the spin conversion efficiency which is to control the interface structure between Ni-Co alloy and non-magnetic spacer Cu spacer layer (Fig.2) [3]. Moreover, we show that even the sign of the MD-CSC can be tuned by changing the non-mangetic spacer material [5]. These findings would be a milestone toward realizing a high-density and energy-efficient spin-orbit torque MRAMs. This work was partly supported by Grant-in-Aid for Scientific Research (Nos. JP16J03105, JP25220604, JP15H05702, and JP19J01643) and CREST program (No. JPMJCR18T3) of JST. Part of this work was conducted at the AIST Nano-Processing Facility, supported by Nanotechnology Platform Program of the Ministry of Education, Culture, Sports, Science and Technologies (MEXT), Japan. 
**References** [1] A. Manchon et.al, Rev. Mod. Phys. 91, 035004 (2019). [2] S. C. Baek et.al, Nat. Mater. 17, 509-513 (2018). [3] Y. Hibino et al., Nat. Commun. 8, 15848 (2021). [4] Y. Hibino et.al, Phys. Rev. B 101, 174441 (2020). [5] Y. Hibino et al., APL Mater. 8, 041110 (2020). 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/bc101a35bb991226ebda3683a9a65441.png)

Clarifying the Origin of Charge to

As the era of Moore's law in transistor based computing comes to an end, it is possible that society will rely on new systems to process information [1]. Nanomagnets are an appealing candidate to supercede transistors as they may theoretically reach the Landauer limit of efficiency at room temperature [2]. Arrays of magnetic material may be patterned in nearly any 2D pattern conceivable and made of a myriad of materials to engineer a wide variety of phases, from standard ferromagnetic order to skyrmions. The interactions between domains creates Ising like behavior which naturally maps onto a variety of computing schemes, such as nanomagnetic logic [3], Hopfield networks [4], and QUBO algorithms [5]. The nonlinear field response even effectively performs the function of a reservoir in the neuromorphic computing framework of "reservoir computing" [6]. This richness of behaviors is messy and more difficult to control than CMOS systems, but offers incredible efficiency and naturally organic structure if given the appropriate problems. Artificial spin ice, nanomagnet arrays patterned to simulate the difficult to study problem of frustrated magnetism [7], has recently branched into the field of nanomagnetic computing. Here we will incorporate principles from artificial spin ice to better understand how interacting nanomagnets process information. We will also introduce a model for the mean-field dynamics of nanomagnets that illuminates how external field can drive collective behavior in such a way that the spin system's dynamics perform useful information processing. We then apply the results of this model to reservoir computing to attain a lower error signal prediction framework comprised of nanomagnets. 

**References:** 
[1] T. Theis, and H-S. P. Wong, Computing in Science & Engineering., Vol. 19.2, p.41-50 (2017) 
[2] B. Lambson, D. Carlton, and J. Bokor, Physical review letters., Vol. 107.1, p.010604 (2011) 
[3] H. Arava, et al, Nanotechnology, Vol. 29.26, p.265205 (2018) 
[4] M. Saccone, et al, Nature Physics, Vol. 18.5, p.517-521 (2022) 
[5] A. Lucas, Frontiers in physics, Vol. 1 p.5 (2014) 
[6] J. Gartside, et al, Nature Nanotechnology, Vol. 17.5, p.460-469 (2022) 
[7] S. Skjærvø, et al, Nature Reviews Physics, Vol. 2.1, p.13-28 (2020)

Premium content

Stability of under/over oxidized magneto ionic states in Pt/Co60Fe20B20/HfO2

Downloads

Next from MMM 2022

Building spintronics neuromorphic systems with Neural Ordinary Differential Equations

Stay up to date with the latest Underline news!

PRESENTATIONS

CONFERENCES

COMPANY

RESOURCES