United States

Two-dimensional van der Waals (vdW) heterostructures are at the forefront of research due to their extensive potential as a platform for spintronics and opto-spintronics applications [1]. Room-temperature ferromagnetism has been achieved in several two-dimensional (2D) magnetic materials and heterostructures [2,3]. Ferromagnetic 2D semiconductors are of particular interest since they allow for simple integration with current silicon-based electronics and their properties can be easily tuned with electric fields and optical excitations. Recently, we demonstrated light tunable magnetism in V-doped WS2 (V-WS2) monolayers, mediated by optically injected charge carriers [4]. A similar effect was shown in ML-VSe2/BL-MoS2 heterostructures in which the magnetization of VSe2 penetrates into the non-magnetic optically active MoS2 layer, allowing for the tunability of the magnetic properties of the heterostructure with light. The VSe2 layer facilitates charge separation, which promotes changes in the magnetization of the MoS2 layer, showing an enhanced light mediated magnetism effect compared to V-WS2. We present a study of related 2D magnetic heterostructures where we compare the magneto-optical response of VSe2/MoS2, VSe2/WS2 and V-MoS2/graphene heterostructures. We propose that, as the VSe2 layer in the VSe2/MoS2 heterostructure allows for charge separation through the interface, graphene in a V-MoS2/graphene heterostructure may play a similar role. The difference between the two systems lies in the source of the magnetism of the semiconducting layer. In the VSe2/MoS2 and VSe2/WS2 systems, the ferromagnetic VSe2 layer is responsible for the proximity magnetism in the non-magnetic MoS2 layer, while in V-MoS2/graphene the semiconducting layer is magnetically doped. Moreover, V-MoS2 shows enhanced magnetic properties when interfaced with graphene, compared to samples grown on Si/SiO2 which may further influence the interaction between the optically injected charge carriers and the magnetic dopants. These findings show how the interactions between photogenerated charge carriers and 2D magnetic semiconductors can be tuned in carefully constructed vdW heterostructures.&lt;br&gt;&lt;br&gt;
**References** [1] J.F. Sierra, J. Fabian, and R.K. Kawakami, Nature Nanotechnology., Vol. 16, p. 856-868 (2021)
[2] F. Zhang, A. Sebastian, D.H. Olson, Advanced Science., Vol. 7, p. 2001174 (2020)
[3] M. Bonilla, S. Kolekar, Y. Ma, Nature Nanotechnology., Vol.13, p. 289-293 (2018)
[4] V. Ortiz Jiménez, Y.T.H. Pham, M. Liu, Advanced Electronic Materials., Vol. 7, p. 21000310 (2021)

MMM 2022

Light mediated magnetism in van der Waals magnetic heterostructures

Two-dimensional van der Waals (vdW) heterostructures are at the forefront of research due to their extensive potential as a platform for spintronics and opto-spintronics applications [1]. Room-temperature ferromagnetism has been achieved in several two-dimensional (2D) magnetic materials and heterostructures [2,3]. Ferromagnetic 2D semiconductors are of particular interest since they allow for simple integration with current silicon-based electronics and their properties can be easily tuned with electric fields and optical excitations. Recently, we demonstrated light tunable magnetism in V-doped WS2 (V-WS2) monolayers, mediated by optically injected charge carriers [4]. A similar effect was shown in ML-VSe2/BL-MoS2 heterostructures in which the magnetization of VSe2 penetrates into the non-magnetic optically active MoS2 layer, allowing for the tunability of the magnetic properties of the heterostructure with light. The VSe2 layer facilitates charge separation, which promotes changes in the magnetization of the MoS2 layer, showing an enhanced light mediated magnetism effect compared to V-WS2. We present a study of related 2D magnetic heterostructures where we compare the magneto-optical response of VSe2/MoS2, VSe2/WS2 and V-MoS2/graphene heterostructures. We propose that, as the VSe2 layer in the VSe2/MoS2 heterostructure allows for charge separation through the interface, graphene in a V-MoS2/graphene heterostructure may play a similar role. The difference between the two systems lies in the source of the magnetism of the semiconducting layer. In the VSe2/MoS2 and VSe2/WS2 systems, the ferromagnetic VSe2 layer is responsible for the proximity magnetism in the non-magnetic MoS2 layer, while in V-MoS2/graphene the semiconducting layer is magnetically doped. Moreover, V-MoS2 shows enhanced magnetic properties when interfaced with graphene, compared to samples grown on Si/SiO2 which may further influence the interaction between the optically injected charge carriers and the magnetic dopants. These findings show how the interactions between photogenerated charge carriers and 2D magnetic semiconductors can be tuned in carefully constructed vdW heterostructures. 
**References** [1] J.F. Sierra, J. Fabian, and R.K. Kawakami, Nature Nanotechnology., Vol. 16, p. 856-868 (2021)
[2] F. Zhang, A. Sebastian, D.H. Olson, Advanced Science., Vol. 7, p. 2001174 (2020)
[3] M. Bonilla, S. Kolekar, Y. Ma, Nature Nanotechnology., Vol.13, p. 289-293 (2018)
[4] V. Ortiz Jiménez, Y.T.H. Pham, M. Liu, Advanced Electronic Materials., Vol. 7, p. 21000310 (2021)

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.

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The manipulation of exchange interactions in two-dimensional magnets has fundamental research value and potential applications. Based on first-principles calculations, the exchange interactions in experimental controversial ferromagnetic 1T-VSe2 monolayer [1,2] are systematically studied. It is found that three shells of nearest-neighbor Heisenberg exchange interactions and higher-order interactions are crucial for an accurate description of the ferromagnetism in 1T-VSe2 monolayer. Based on the understanding of tuning the magnetic interactions and the magnetic ground state in 1T-VSe2 monolayer by external factors, two modulation methods, alkali metal Lithium adsorption and electride Ca2N substrate, are proposed. In both systems, the strongly frustrated Heisenberg exchange interactions compete with higher-order exchange interactions, Dzyaloshinskii-Moriya interaction and magnetocrystalline anisotropy, leading to complex magnetic ground states, such as antiferromagnetic spin spiral, periodical antiferromagnetic cycloidal state and double row-wise antiferromagnetic states. These results highlight the effective manipulation of exchange interactions in two-dimensional magnets. 
This work was supported by the National Natural Science Foundation of China (51871161 and 52071233).
**References** [1] M. Bonilla, S. Kolekar, Y. Ma, et al. Nat. Nanotechnol. 13, 289 (2018). 
[2] P. K. J. Wong, W. Zhang, F. Bussolotti, et al. Adv. Mater. 31, 1901185 (2019). 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/a744a8ab47780f8c1f88b39c20ef4401.png)

Tuning exchange interactions in 1T VSe2 monolayer by alkali metal adsorption and electride substrate

Antiferromagnets (AFMs) are strong candidates for future spintronic applications largely because of their fast dynamics and lack of stray fields. For the required switching of the Néel vector (staggered magnetization), the predicted current-induced bulk Néel spin-orbit torque (NSOT) (1) is most promising. Only two compounds with the required symmetry are known: for both CuMnAs (2,3) and Mn2Au (4,5) experimental evidence for current-induced NSOT was shown based on a small modification of the AFM domain pattern. However, the significance of NSOT for current-induced manipulation of Neel vector orientation stays controversial because competing heating-related mechanisms result in similar effects (6-8).
Here, we investigate the effect of current pulsing with different lengths along the different crystallographic directions on the AFM domain pattern of epitaxial Mn2Au (001) thin films. In-situ imaging of AFM domains before and after the current pulses was performed using x-ray magnetic linear dichroism photoemission electron microscopy (XMLD-PEEM). Reversible and repeated 90° Neel vector rotation of essentially the complete active area of the pattern cross structures was observed (Fig. 1).
Switching was only observed for current parallel to the easy crystallographic axis resulting in a Néel vector rotation perpendicular to the pulse direction, which is consistent with the NSOT. The required current density for switching is essentially independent of the pulse length (10 µs to 1 ms) indicating that thermal activation or other thermal effects are not significant. For current pulses applied parallel to a <100> hard axis, inversion of the current pulse polarity led to a partially reversible motion of domain walls, which is consistent with the NSOT acting on them. Our results confirm the fundamental role of NSOT for current-induced Néel vector switching in Mn2Au, providing an effective mechanism for spintronics applications. 

**References:** 
(1) J. Zelezný H. Gao, K. Výborný et al., Phys. Rev. Lett. 113, 157201 (2014). 
(2) P. Wadley, B. Howells, J. Zelezný et al., Science 351, 587 (2016). 
(3) P. Wadley, S. Reimers, M. J. Grzybowski et al., Nat. Nanotechnol. 13, 632 (2018). 
(4) S. Bodnar L. Smejkal, I. Turek et al., Nat. Commun. 9, 348 (2018). 
(5) S. Y. Bodnar, M. Filianina, S. P. Bommanaboyena et al., Phys. Rev. B 99, 140409(R) (2019). 
(6) T. Matalla-Wagner, J.-M. Schmalhorst, G. Reiss et al., Phys. Rev. Res. 2, 033077 (2020). 
(7) H. Meer, O. Gomonay, C. Schmitt et al., arXiv:2205.02983v1 [cond-mat.mtrl-sci]. 
(8) H. Meer, F. Schreiber, C. Schmitt et al., Nano Lett.21, 114-119 (2020). 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/c2d61688e7f3764ada5a6f19abed7e66.png)

Néel spin orbit torque induced remnant switching of the Néel vector in antiferromagnetic Mn2Au

Orthoferrites (REFeO3) containing rare-earth (RE) elements are 3D antiferromagnets (AFM) that exhibit characteristic weak ferromagnetism originating due to slight canting of the spin moments and display a rich variety of spin reorientation transitions in the magnetic field (H)-temperature (T) parameter space (1, 2). We present spin Hall magnetoresistance (SMR) studies (3) on a b-plate (ac-plane) of crystalline Ho0.5Dy0.5FeO3│Pt hybrid at various T in the range, 11 to 300 K. In the room temperature Γ4(Gx, Ay, Fz) phase, the switching between two degenerate domains, Γ4(+Gx, +Fz) and Γ4(-Gx, -Fz) occurs at fields above a critical value, Hc ≈ 713 Oe. Under H > Hc, the angular dependence of SMR (α-scan) in the Γ4(Gx, Ay, Fz) phase yielded a highly skewed curve with a sharp change (sign-reversal) along with a rotational hysteresis around a-axis. This hysteresis decreases with an increase in H (Fig.1). Notably, at H < Hc, the α-scan measurements on the single domain, Γ4(± Gx, ± Fz) exhibited an anomalous sinusoidal signal of periodicity 360 deg. Low-T SMR curves (H = 2.4 kOe), showed a systematic narrowing of the hysteresis (down to 150 K) and a gradual reduction in the skewness (150 to 52 K), suggesting weakening of the anisotropy possibly due to the T-evolution of Fe-RE exchange coupling. Below 25 K, the SMR modulation showed an abrupt change around the c-axis, marking the presence of Γ2(Fx,Cy,Gz) phase. We have employed a simple Hamiltonian and computed SMR to examine the observed skewed SMR modulation. In summary, SMR is found to be an effective tool to probe magnetic anisotropy as well as a spin reorientation in Ho0.5Dy0.5FeO3. Our spin-transport study highlights the potential of Ho0.5Dy0.5FeO3 for future AFM spintronic devices. 

**References:** 
(1) T. Yamaguchi, J. Phys. Chem. Solids, Vol. 35, p.479 (1974) 
(2) T. Chakraborty and S. Elizabeth, J. Magn. Magn. Mater., vol. 462, p. 78 (2018) 
(3) Y.-T. Chen, S. Takahashi, H. Nakayama, Phys. Rev. B, vol. 87, p. 144411 (2013) 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/67800cc3e324dc52f0e3f5cd105e838b.png)

Probing magnetic anisotropy and spin reorientation transition in 3D antiferromagnet, Ho0.5Dy0.5FeO3 │Pt using spin Hall magnetoresistance

Recently, two-dimensional (2D) materials have emerged as a replacement for heavy metals (HM) because of their large spin-charge interconversion efficiency [1]. In this work, we explore a promising and relatively less explored 2D monochalcogenide SnS for spintronics application. Through symmetry arguments, it is proposed that SnS should exhibit unconventional spin-orbit torques (SOTs), which is very important for energy-efficient switching of magnets with perpendicular magnetic anisotropy (PMA) [1]. SnS thin films up to monolayer (ML) thickness have been grown on Si/SiO2 substrates using pulsed laser deposition (PLD) technique at 200 °C and room temperature (RT). Two typical Raman active modes (Ag and B3g) [2] can be distinguished in the acquired Raman spectra [Fig. 1]. We performed spin-torque ferromagnetic resonance (STFMR) measurements to investigate the SOTs in SnS/Ni80Fe20 system. For ST-FMR measurements, we fabricated SnS/Ni80Fe20 rectangular microstrips using the lift-off technique. For STFMR measurements, an in-plane RF current of frequency varying from 4 GHz to 8 GHz was applied to the bilayer in the presence of an external magnetic field (H). We measured the voltage (Vmix) across the device, which originated due to the mixing of AMR and RF current. We determine the in-plane and out-of-plane torque components by fitting the Vmix with a sum of symmetric and antisymmetric Lorentzian. We performed a complete angular dependence of the STFMR signal by varying the magnetization angle φ in the sample plane. In addition to a conventional sin2φcosφ (Vy,s) dependence, we found sin2φ (Vz,s) dependence [Fig. 2], which is a signature of unconventional out-of-plane anti-damping like torque [3]. Thus our results suggest that SnS can be used to achieve efficient switching of magnetic devices with PMA via the strong unconventional out-of-plane anti-damping like torque. 
**References** [1] Y. Liu et. al., ACS Nano 14, 9389 (2020).
[2] A.N. Mehta et. al., J. Microsc. 268, 276 (2017).
[3] D. MacNeill, et al., Nat. Phys. 13, 300 (2017). 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/1e469b41dfe570761dd64ff3b4f4fb50.png)

Evidence of unconventional spin orbit torque in SnS/Ni80Fe20 heterostructures

Spin-orbit torques (SOTs) originating from a ferromagnetic spin source have attracted much attention for spintronics devices because they offer field-free switching of perpendicular magnetization [1]. Cobalt-based Heusler alloy Co2MnAl (CMA) is attractive for the ferromagnetic spin source because it is theoretically predicted to be a magnetic Weyl semimetal with strong spin-orbit interaction [2]. In this work, we demonstrated SOT-induced magnetization switching for a perpendicularly magnetized CoFeB (CFB) under zero magnetic field by using an in-plane magnetized CMA spin source. We also measured modulation of coercive field by the SOTs and investigated the effective perpendicular magnetic field Heff induced by them.
A heterostructure consisting of, from the substrate side, MgO(10)/CMA(5)/Ti(3)/CoFeB(1.2)/MgO(3)/Ta(1) was deposited on an MgO(100) substrate (numbers in parentheses are nominal thickness in nm). Then, the stack was processed into Hall-bar devices with a 5-μm-wide channel. From measurements on transverse resistance Ryx reflecting the anomalous Hall effect (AHE), the CFB layer showed a clear perpendicular magnetic easy axis, whereas the CMA had an in-plane magnetic easy axis. After aligning magnetization of CMA, MCMA, to parallel or antiparallel to the channel direction, we studied SOT-induced magnetization switching of CFB layer by applying current pulses Ipulse to the channel in the absence of magnetic field. Clear field-free switching of CFB magnetization was observed in both cases. The polarity of SOT-induced magnetization switching with respect to Ipulse was reversed depending on the relative direction of MCMA to Ipulse (Fig. 1). Furthermore, we investigated Heff induced by SOTs with Heff = [Hc(+I) - Hc(-I)]/2, where Hc(I) is a coercive field determined from AHE measurements, and I is a channel current. We observed sizable effective field of μ0Heff = 1 mT at I = 3 mA. Importantly, the sign of Heff was also reversed depending on the relative direction of MCMA to I. These results suggest that the possible origin of the SOTs is spin-orbit precession [1]. 
**References** [1] S. C. Baek et al., Nat. Mater., Vol. 17, p.509 (2018)
[2] J. Kübler, C. Felser, EPL, Vol. 114, 47005 (2016)
 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/f3b6d6e21fe57677f13c58736dcdc62f.png)

Field free switching of perpendicular magnetization by spin

Current-induced type-x spin-orbit-torque (SOT) switching configuration describes the orthogonal relationship between the magnetic easy-axis (EA) of ferromagnetic (FM) layer and the injected spin polarization σ from heavy metal (HM) layer, which has potential to eclipse the conventional type-y scenario (EA∥σ) at short pulse regime [1,2].
In this study, we systematically investigate type-x SOT switching properties in HM/FM heterostructures. First, through macrospin simulations, we demonstrate that deterministic type-x switching can be realized by applying an assisting z-direction external field (Hz) or by introducing a canted EA. From current pulsed width (tpulse) dependent simulations, we observe that the critical switching current (Isw) of type-x is indeed smaller than that of type-y in the sub-ns regime [Fig. 1(a)]. By further considering a positive field-like SOT (FLT) in the simulated system, type-x switching mode results in a lower Isw than that of type-y when tpulse < 10 ns [Fig. 1(b)], suggesting the advantage of employing the type-x design with material system having sizable FLTs.
Accordingly, we choose W/CoFeB bilayer structure, which has a sizable FLT, to experimentally observe type-x SOT switching in micron-sized devices. By utilizing current-sensed differential planar Hall signal [3], the field-free type-x switching is observed for both positively and negatively y-canted devices [Fig.2 (a) and (b)], with opposite switching polarities. A z-direction internal field originated from the canted EA in concert with the damping-like SOT is observed by analyzing Hz-assisted switching phase diagram. Under the zero-field condition, as canting angle (φEA) increases, the switching dynamics evolves from a pro-type-x scenario to a pro-type-y scenario [Fig.2 (c) and (d)]. Our systematic work therefore verifies the advantage of canted EA for field-free type-x SOT applications, which can be informative for designing more efficient next generation SOT-MRAMs. 
**References** [1] S. Fukami, T. Anekawa, C. Zhang, and H. Ohno, A spin-orbit torque switching scheme with collinear magnetic easy axis and current configuration, Nat. Nanotechnol. 11, 621 (2016).
[2] S. Fukami, T. Anekawa, A. Ohkawara, Z. Chaoliang, and H. Ohno, A sub-ns three-terminal spin-orbit torque induced switching device, IEEE Symposium on VLSI Technology, 61 (2016).
[3] G. Mihajlović, O. Mosendz, L. Wan, N. Smith, Y. Choi, Y. Wang, and J. A. Katine, Pt thickness dependence of spin Hall effect switching of in-plane magnetized CoFeB free layers studied by differential planar Hall effect, Appl. Phys. Lett. 109, 192404 (2016). 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/02c77fb33b20421ea076c810343bd497.png)

Anatomy of Type x Spin

Magnon-induced switching of nanomagnets is one of the key milestones to realize magnon-based in-memory computing. Spin waves (magnons) have been reported to move domain walls [1] and induce the reversal of Ni81Fe19
(Py) nanostripes (NSs) fabricated on YIG [2]. We report the observation of magnon-induced reversal of bistable nanomagnets
by time-resolved Brillouin light scattering microscopy. We used Py nanostripes separated from YIG via an intermediate insulating layer (Fig. 1). Thereby, we suppressed the interlayer
exchange interaction between Py and YIG. A coplanar waveguide (CPW) was fabricated on top of an array of Py NSs. The device performed as a grating coupler [3]. Short-wave magnons
were emitted into YIG which then propagated underneath remotely positioned nanostripes. We saturated the device at +80 mT and then decreased the field to -24 mT. We measured the
thermal magnon spectrum of the unswitched Py NSs before magnon emission. After magnon excitation we observed characteristic modifications in the magnon spectrum (Fig. 2). Beyond a
critical power level, peak A and peak B vanished and a new peak B’ appeared. These specific modifications indicated the reversal of the nanomagnets and occurred for both the pulsed and
continuous wave magnon excitation. Our experimental data suggest that dipolar coupling is sufficient to achieve magnon-induced switching. We report experiments performed in the linear
and non-linear regime of magnon excitation. The latter experiments are important for the realization of recurrent neural networks based on ferromagnet/ferrimagnet hybrid structures as
proposed in Ref. [4]. Our results suggest that the storage of magnon signals in reversed magnetic bits become possible thus paving the way towards magnon-based in-memory computing
platforms. We acknowledge the financial support from SNSF via Grant No. 197360.
**References** [1] J. Han, P. Zhang, J.T. Hou, Science, Vol. 366, 1121-1125 (2019)
[2] K. Baumgaertl, D. Grundler, submitted
[3] H. Yu, G. Duerr, R. Huber, Nature Communications, Vol. 4, 2702 (2013)
[4] Á. Papp, W. Porod, G. Csaba, Nature Communications, Vol. 12, 6422 (2021) 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/1653d0542e758234cbf15706681182ba.png) 

Sketch of the device. An oscillating current is injected in the CPW to excite magnons which propagate in the bare YIG until reaching separately positioned Py nanostripes. Each material
thickness is indicated between parenthesis. 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/7dbebbbdfc15c50c042108e45acd650e.png) 

BLS thermal magnon spectra on Py stripes before (magenta) and after (black) magnon excitation at -24 mT.

Reversal of nanostructured ferromagnets by magnon pulses in underlying yttrium iron garnet

The number of experimental techniques, and their capability to measure and image magnetic behavior, is constantly increasing. Analogously, the ability to computationally study magnetic systems using techniques such as micromagnetics or Monte Carlo is also growing. However, it is often not trivial to combine experimental and computational results such that one can predict the results of experimental techniques directly from computational magnetization structures. We have produced the Python software package mag2exp [1], which integrates with the micromagnetic simulation environment Ubermag [2, 3], and enables realistic virtual experiments to be easily and quickly performed on magnetic structures using a range of experimental techniques. These techniques include Lorentz transmission electron microscopy, magnetic force microscopy, x-ray holography, small angle neutron scattering, torque magnetometry, along with other useful experimental capabilities. The mag2exp software is compatible with Jupyter Notebook allowing for the visualization of data and documentation of the entire simulation workflow, thus making the research more reproducible and re-usable [4]. This package aims to help bridge some of the gap between computational simulations and experiments, leading to the potential for simulations to inform real world experiments and vice versa. Here, we show how the mag2exp package can be used to study the magnetic behaviors for the system under investigation by converting a digital magnetization field to an experimental result. We also present the results of using the experimental techniques included in mag2exp on complex magnetization structures created using micromagnetic simulations such as magnetic skyrmions, vortices, and other solitons. This work was financially supported by the EPSRC Program grant on Skyrmionics (EP/N032128/1). 

**References** 
[1] S. J. R. Holt, et al., https://github.com/ubermag/mag2exp
[2] M. Beg, et al., IEEE Trans. Magn. 58, 2 (2022)
[3] https://ubermag.github.io/
[4] M. Beg, et al., Comput. Sci. Eng., 23, 2 (2021) 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/e5878ed02d7e62c1698f06e7654e1759.png) 

Small angle neutron scattering pattern generated by mag2exp of a micromagnetic skyrmion lattice. 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/97f47cd2323072677233a5b05b6689cb.png) 
X-ray holography image generated by mag2exp of a mixed magnetization state.

mag2exp: Simulating experimental techniques from computational micromagnetics

Studies of Giant Magnetoimpedance (GMI) effect have attracted considerable attention considering various technological applications [1,2]. Up to now, most attention has been paid to the achievement of the highest GMI as well as to tailoring of the magnetic field dependence of GMI effect through the modification of the magnetic anisotropy of the magnetic materials. Generally, the magnetic anisotropy of amorphous materials can be controlled by the magnetostriction coefficient (that to great extend is linked to the chemical composition of material) or by special thermal treatment (including magnetic field or stress-annealing) [2,3]. Most of studies of GMI effect are performed in different families of magnetic wires [1-3]. 
Recently, a new approach allowing to tune the magnetic anisotropy of magnetic wires by depositing of magnetic and non-magnetic layers onto the glass-coating [4].
Accordingly, the purpose of this paper is to study the GMI effect in amorphous Co-rich microwires with Co- layers deposited onto glass-coating. 
Studies of magnetic properties and GMI effect of as-prepared amorphous Fe3.6Co69.2Ni1B12.5Si11Mo1.5C1.2 and of the same microwires with deposited Co-layer microwires reveals that both samples present soft magnetic properties and high GMI effect. Low field hysteresis loops of both samples are rather similar, while the contribution of Co-layer is observed in hysteresis loop measured at higher magnetic field (see Figs 1a,b). Such character of hysteresis loop is similar to those observed in microwires with mixed amorphous- crystalline structure [5]. However, the GMI ratio, ΔZ/Z and magnetic field, H, dependences of GMI effect are affected by the Co-layer (see Fig.2). In particularly, higher GMI ratio and sharper peaks on ΔZ/Z (H) dependencies. 
We discussed observed experimental dependences considering both change of the internal stresses originated by the Co-layer as well as the magnetostatic interaction between the amorphous ferromagnetic nucleus and deposited Co Layer. 
**References:** 
[1] T. Uchiyama, K. Mohri, and Sh. Nakayama, IEEE Trans. Magn., 47, No 10 (2011) pp. 3070-3073 
[2] F.Qin, H.-X. Peng, Prog.Mater. Sci,58 (2013) 183–259 
[3] A. Zhukov, et.al. J. Alloys Compound 814 (2020) 152225, 
[4] K.R. Pirota, M. Hernandez-Velez, D. Navas, A. Zhukov and M. Vázquez, Adv. Funct. Mater. 14 No 3 (2004) 266-268. 
[5] V. Zhukova, et.al. , Chemosensors, 9 (2021) 100, doi: https://doi.org/10.3390/ chemosensors9050100 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/fcd16c5915024c52cc375c38ac9ea4a7.png) 
Fig.1 Low field (a) and high field hysteresis loops of studied microwires 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/1b1cb1408a5636b26250156f0a2b3a1b.png) 
Fig.2. ΔZ/Z (H) dependencies of microwire without Co-layer (a) and with Co-layer deposited onto glass-coating (b)

Magnetic properties and giant magnetoimpedance effect in multilayered microwires

Interlayer DMI (IL-DMI) has been recently predicted and observed in multilayer thin film heterostructures1-3, coupling two neighboring magnetic films via a non-magnetic interlayer in a chiral fashion. IL-DMI could be utilized to obtain complex chiral magnetic states in one layer, controlled by the magnetic configuration of a neighboring layer, of great interest to spintronic applications. Previous work using magnetometry techniques indicates the existence of non-zero IL-DMI in Synthetic Antiferromagnetic (SAF) bilayers with highly asymmetric properties; one layer close to the spin reorientation transition, and the other fully out-of-plane. In these systems, IL-DMI is manifested as a chiral exchange bias under in-plane magnetic fields. In this contribution, we further investigate these systems via a combination of X-ray magnetic scattering and imaging techniques, revealing the presence of periodic chiral magnetic structures. In particular, X-ray Magnetic Circular Dichroism Photo Electron Emission Microscopy (XMCD-PEEM) measurements evidence the formation of ring-like structures of sizes after applying a field cycling protocol (Fig. 1). In order to understand more in detail the magnetic configuration of these textures, we reconstruct the spatially resolved magnetization vector by combining different relative sample-beam XMCD projections, yielding the presence of 360 degree domain walls separating the outer and inner domains. During the presentation, we will discuss in detail the role that IL-DMI and other magnetic interactions play in the formation and shape of these rings.

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