United States

Current-induced spin-orbit torque (SOT) is an efficient mechanism to manipulate the magnetization in magnetic materials [1]. In principle, the sizable SOT is believed to originate from the bulk spin Hall effect (SHE) and/or the interfacial spin Rashba- Edelstein effect (SREE) in heavy metals (HMs)-based magnetic heterostructures with strong spin-orbit coupling (SOC). Strikingly, recent reports suggest that the light metals (LMs) can also generate non-negligible SOTs and these sizable charge-to-spin conversions are attributed to the orbital angular momentum (OAM) induced orbital Hall effect (OHE) and/or orbital Rashba-Edelstein effect (OREE) [2]. The OAM dominating SOT generation has been experimentally explored in various LM-based systems such as Ti, Cr, and Cu-based magnetic heterostructures [3].
In this work, we prepare the Pt/Co/CuNx perpendicular magnetic heterostructures by reactive sputtering. By controlling the doping concentration, the overall SOT efficiency can be tuned from 6% to ~ 40%. The enhancement is attributed to combining the spin currents from Pt and the orbital currents generated by the nitrided Cu capping layer. Besides the conventional SOT characterizations, we further demonstrate the neuromorphic switching and show that the orbital currents can effectively manipulate the perpendicular magnetization. These results provide valuable information for building energy-efficient spin-orbitronic devices utilizing both the spin and the orbital effects [4].&lt;br&gt;&lt;br&gt;
**References** [1] L. Liu et al., Science 336, 555 (2012).
[2] D. Lee et al., Nature Communications 12, 6710 (2021).
[3] S. Lee et al., Communications Physics 4, 234 (2021).
[4] T.-Y. Chen et al., Physical Review Applied 17, 064005 (2022).&lt;br&gt;&lt;br&gt;
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MMM 2022

Spin orbit torque switching mediated by orbital currents from CuNx

Current-induced spin-orbit torque (SOT) is an efficient mechanism to manipulate the magnetization in magnetic materials [1]. In principle, the sizable SOT is believed to originate from the bulk spin Hall effect (SHE) and/or the interfacial spin Rashba- Edelstein effect (SREE) in heavy metals (HMs)-based magnetic heterostructures with strong spin-orbit coupling (SOC). Strikingly, recent reports suggest that the light metals (LMs) can also generate non-negligible SOTs and these sizable charge-to-spin conversions are attributed to the orbital angular momentum (OAM) induced orbital Hall effect (OHE) and/or orbital Rashba-Edelstein effect (OREE) [2]. The OAM dominating SOT generation has been experimentally explored in various LM-based systems such as Ti, Cr, and Cu-based magnetic heterostructures [3].
In this work, we prepare the Pt/Co/CuNx perpendicular magnetic heterostructures by reactive sputtering. By controlling the doping concentration, the overall SOT efficiency can be tuned from 6% to ~ 40%. The enhancement is attributed to combining the spin currents from Pt and the orbital currents generated by the nitrided Cu capping layer. Besides the conventional SOT characterizations, we further demonstrate the neuromorphic switching and show that the orbital currents can effectively manipulate the perpendicular magnetization. These results provide valuable information for building energy-efficient spin-orbitronic devices utilizing both the spin and the orbital effects [4]. 
**References** [1] L. Liu et al., Science 336, 555 (2012).
[2] D. Lee et al., Nature Communications 12, 6710 (2021).
[3] S. Lee et al., Communications Physics 4, 234 (2021).
[4] T.-Y. Chen et al., Physical Review Applied 17, 064005 (2022). 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/8f0fb0ea18b1a4f2b0a17ef693b20045.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.

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Multiferroic hetereostructures consist of two types of ferroic materials, typically a ferroelectric and ferromagnet, linked together through interfacial interactions, often a magnetostrictive mechanism[1]. In these types of multiferroics the strain associated with the ferroelectric polarization sets a microscopic anisotropy that couples the ferroelectric domains to ferromagnetic domains[2]. These multiferroics offer interesting spin textures that can be controlled by a range of techniques which, if functionalized, could result in lower power spintronic devices. Here we use multiferroics based on BaTiO3(111) substrates in which the strain has a heavy dependence on the temperature. Measurements of anisotropy are taken using a Kerr microscope in an optical cryostat. Figure 1 shows that there are three distinct regions of interest corresponding to the different crystal phases of BaTiO3: tetragonal (T) at room temperature, orthorhombic (O) below 280K and rhombohedral (R) below 190K. The greatest region of anisotropy change is close to room temperature at the orthorhombic phase transition, with another significant region around the rhombohedral transition. This tunability is important when considering the domain structure. Depending on the orientation in which a magnetic field is applied[3], the magnetization can rotate in either a head-to-tail (uncharged) or head-to-head (charged) fashion. Figure 2 shows by micromagnetic simulations informed by experiments that it is possible to control domain wall width through temperature alone. Our results show that this change is heavily non-linear with temperature and show the most pronounced change in charged domain walls with a change of ~100% going from the tetragonal to rhombohedral phase. This could be exploited in a temperature activated spintronic device.

Temperature Dependence of Magnetic Anisotropy and Domain Tuning in BaTiO3(111)/CoFeB Multiferroic Heterostructures

Scalable implementation of fault-tolerant quantum computing [1] requires selective addressing of qubits. This is challenging when such qubits are discrete points or regions on a lattice at nanoscale dimensions as it is difficult to localize and confine a classical divergence-free field to a small volume in space. We propose a new technique for individual control of spin qubits [2,3] implemented with induced field of nanomagnets using voltage control of magnetic anisotropy (VCMA) [4]. We show that by tuning the frequency of the nanomagnet’s electric field drive to the Larmor frequency of the spins confined to a nanoscale volume, and by modulating the phase of the drive, single-qubit quantum gates with fidelities approaching those for fault-tolerant quantum computing [1] can be implemented. Such single-qubit gate operations are energy efficient, requiring only tens of femto-Joules per gate operation, lossless, and purely magnetic field control (no E-field over the target volume). Furthermore, while our initial motivation for using a qubit comprising an ensemble ~10-100 spins is to improve signal to noise ratio for read out, we will investigate if exchange coupling between them can mitigate dephasing and further improve single qubit gate fidelity. 
**References** [1] Gottesman, D. Phys. Rev. A 57, 127–137 (1998). URL https://link.aps.org/doi/10. 1103/PhysRevA.57.127.
[2] Cory, D. G., Fahmy, A. F. & Havel, T. F. Proc. Nat. Acad. Sci. (USA) 94, 1634–1639 (1997). URL https://www.pnas.org/content/94/5/1634.
[3] Gershenfeld, N. A. & Chuang, I. L. Science 275, 350–356 (1997). URL https://science. sciencemag.org/content/275/5298/350.
[4] Wang, K. L., Lee, H. & Amiri, P. K. IEEE Transactions on Nanotechnology 14, 992–997 (2015).
[5] Niknam, M., Chowdhury, M.F.F., Rajib, M.M., Misba, W.A., Schwartz, R.N., Wang, K.L., Atulasimha, J. and Bouchard, L.S., 2022. arXiv preprint arXiv:2203.16720. 

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Quantum control of spin qubit ensembles with nanomagnets: Exchange coupling for high fidelity

Among the Mn-based Heusler ferrimagnets are a number of topical materials for the emerging field of Antiferromagnetic Spintronics, combining low moments, high spin-polarisation and anisotropy. In a recent work (1), we described the long-range spatial oscillation of the spin-transfer torque (STT) in magnetic tunnel junctions (MTJs) based on tetragonal (DO22) Mn3Ga (2), present both in Fe/MgO/Mn3Ga and in Mn3Ga/MgO/Mn3Ga tri-layers. Using first principles ballistic non-collinear spin transport (NEGF+SDFT) (3,4), we related the STT oscillation to the mismatch of the Fermi wavevectors of the majority and minority D1 symmetry band in Mn3Ga in the direction of transport. We studied the high-bias TMR effect in these stacks and found, for the symmetric MTJs, a maximum value of over 100% and a sign change below 1V, in accordance with experimental observations for similar ferrimagnetic MTJs (5).
Another Mn-based Heusler Mn3Al has been shown to exhibit half-metallicity and almost ideally fully compensated moment in its cubic DO3 phase (6) and proposed MTJs with GaAs have shown large theoretical TMR ratios (7). Our ab initio geometry optimisation of Mn3Al revealed a stable tetragonal DO22 solution with almost fully compensated moment (<0.002 μB/f.u.) and an in-plane lattice constant commensurate with MgO, which prompted a study of a familiar tri-layer. As geometrically the Mn3Ga and Mn3Al stacks with MgO are very similar, this could offer further insights about their Spintronic capacity. Here we compare the spin-dependent transport properties of two such junctions (3ML MgO spacer, see Fig. 1(a)). We find that Mn3Al is half-metallic (lacking a majority spin channel at EF) in the direction of transport (Fig.1 (d)), which results in an enormous TMR effect (Fig.1 (c)), but also in the suppression of the long-range STT oscillation (Fig.1 (b)) and a faster decay of the STT with the barrier thickness. The STT is significant in magnitude (1) and pushes both interfacial spins in the same direction (clockwise in Fig.1 (a)). In view of the above, aluminium-rich solid solutions of Mn3Al-Mn3Ga could offer enhanced low-bias TMR performance, while preserving tetragonality, at manageable growth-induced strain, in practical device stacks. 

**References:** 
(1) M. Stamenova, P. Stamenov, F. Mahfouzi, et al., Phys. Rev. B, vol. 103, 094403 (2021). 
(2) K. Rode, N. Baadji, D. Betto, et al., Phys. Rev. B, vol. 87, p. 184429 (2013). 
(3) A. R. Rocha and S. Sanvito, Phys. Rev. B, vol. 70, p. 094406 (2004). 
(4) M. Stamenova, I. Rungger, S. Sanvito, et al. Phys. Rev. B, vol. 95, p. 060403(R) (2017); I. Rungger, A. Droghetti and M. Stamenova, Non-equilibrium Green's functions methods for spin transport and dynamics. In: Andreoni W., Yip S. (eds) Handbook of Materials Modeling, Springer (2018). 
(5) K. Borisov, D. Betto, Y.C. Lau, et al., Appl. Phys. Lett., vol. 108, p. 192407 (2016). 
(6) M. E. Jamer, Y. J. Wang, et al., Phys. Rev. Applied 7, 064036 (2017). 
(7) M. Qiu, Sh.Ye, et al. J. Phys. D: Appl. Phys. 54 115002 (2021). 

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Ab initio comparison of spin transport properties in ferrimagnetic tunnel junctions based on Mn3Ga and Mn3Al

Recently, topological insulator(TI)/ferromagnetic(FM) systems, such as Bi2Se3/FM [1,2], Bi1-xSbx/FM [3,4] have attracted much attention with their promising properties for emerging memory technologies, such as magnetic random-access memories(MRAM). Indeed, these systems may drastically reduce the writing current using spin-orbit torque(SOT) switching. In this case SOT is generated by injecting a charge current into the TI topologically protected surface states(SS), then converted into a spin current in the FM layer. The charge current may shunt the TI SS through the metallic FMs which conductivity is often higher and may not contribute efficiently to the SOT[5]. Thus, FMs with lower conductivities are required and may help to better understand the SOT effect. Also, for applications, FMs with high Curie temperature and perpendicular magnetic anisotropy(PMA) are desirable.

In this work, we focused on the molecular beam epitaxy (MBE) growth conditions of Bi1-xSbx(top)/MnxGa1-x(bottom) heterostructure on the semi-insulating GaAs(001) substrate. A high epitaxial quality was confirmed by the high-resolution scanning transmission electron microscopy (STEM) as shown in Fig.1. The Bi0.85Sb0.15 top surface states have been characterized by performing ARPES measurements. Electronic band structure with topological surface states was observed. Mn0.45Ga0.55 exhibit a PMA with a magnetization of 315 kA/m.

To investigate the charge-to-spin current conversion of Bi0.9 Sb0.1(9 nm)/Mn0.45Ga0.55(7 nm) we first performed anomalous Hall effect (AHE) measurements at various temperatures. A large value of ΔRAHE = 0.4Ω was obtained at room temperature. We then perform second harmonic Hall voltage measurements in order to quantify the damping-like HDL(Fig.2.) and field-like SOT HFL by applying an ac current and in-plane external magnetic field. For this relatively large MnGa thickness (7nm), a value of HDL=2.6±1.3mT for a current density of 1010 A/m2 was estimated. Part of future work will focus on controlling the growth of a thinner layer. 
**References** [1] Mellnik, A. et al. Spin-transfer torque generated by a topological insulator. Nature 511, 449–451 (2014)
[2] Wang, Y., Zhu, D., Wu, Y. et al. Room temperature magnetization switching in topological insulator-ferromagnet heterostructures by spin-orbit torques. Nat Commun 8, 1364 (2017).
[3] Fan, T., Khang, N.H.D., Nakano, S. et al. Ultrahigh efficient spin orbit torque magnetization switching in fully sputtered topological insulator and ferromagnet multilayers. Sci Rep 12, 2998 (2022)
[4] Tuo Fan, Nguyen Huynh Duy Khang, Takanori Shirokura, Ho Hoang Huy, and Pham Nam Hai , Low power spin–orbit torque switching in sputtered BiSb topological insulator/perpendicularly magnetized CoPt/MgO multilayers on oxidized Si substrate, Appl. Phys. Lett. 119, 082403 (2021)
[5] Liu, L. et al. Spin-torque switching with the giant spin Hall efect of tantalum. Science 336, 555–558 (2012) 
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Growth, characterization and spin orbit torque of BiSb topological insulator/MnGa perpendicular ferromagnet systems

Spin-orbit torque (SOT) switching devices fabricated by combining van der Waals (vdW) based semiconducting ferromagnets (FMs) and Weyl semimetal (WSMs) are appealing because of electric field-controlled magnetism and unconventional charge to spin conversion, which can be exploited for modular memory and logic devices. For instance, the vdW based FM semiconductors, such as Cr2Ge2Te6 (CGT), offer us the opportunity to study SOT devices where electric field-controlled magnetism can be used for enhanced device functionalities1. Also, we have recently shown that field-free deterministic switching of perpendicular magnet can be obtained by utilizing the unconventional spin orbit torque in WTe22. In SOT switching devices, the electrical readout of the semiconducting FM layer is essential for device functionality. Electrical detection of magnetization in conventional insulating/ semiconducting ferromagnet (FM) is routinely achieved by utilizing the spin hall effect generated by the adjacent heavy metal layer3. The electrical readout of magnetization in 2D semiconducting FM has been demonstrated by coupling Cr2Ge2Te6 with heavy metals4 and topological insulators5. However, few reports have shown electrical detection in a vdW based semimetal/FM-semiconductor heterostructures. As shown in Fig. 1, our initial measurements have demonstrated electrical detection of magnetization in Cr2Ge2Te6 by measuring the anomalous Hall resistance in WTe2/CGT bilayers. On the same device, the resistance of individual CGT is more than 100 times higher than the resistance of the bilayer structure as plotted in Fig .2, therefore most of the current is flowing through the WTe2 layer. We will present detailed measurements, which are required to understand the observed anomalous Hall effect induced at the interface in WTe2/CGT bilayer systems. 
**References** 1. I. A. Verzhbitskiy, H. Kurebayashi and H. Cheng, Nat. Electron., Vol. 3, p.460 (2020).
2. IH. Kao, R. Muzzio and H. Zhang, Nat. Mater. (2022).
3. A. S. Ahmed, A. J. Lee and N. Bagués, Nano Lett., Vol. 19(8), p.5683 (2019).
4. V. Gupta, T. M. Cham and G. M. Stiehl, Nano Lett., Vol. 20(10), p.7482 (2020).
5. V. Gupta, R. Jain and Y. Ren, arXiv:2206.02537 (2022). 
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Electrical detection of magnetization of a layered semiconducting ferromagnet using WTe2

Energy-efficient spintronic memories and oscillators require a large spin-orbit torque (SOT) and low effective damping for exciting magnetic precession. Conventional
SOT-driven bilayers, consisting of a heavy metal and an ultrathin ferromagnet (e.g., ~1 nm), suffer from high damping due to interfacial spin pumping and scattering. Recently, SOTs have
been reported in thicker (~10 nm) single-layer ferromagnetic films with vertical compositional gradients [1-3]. We hypothesize that thick vertically graded ferromagnets can also enable
low damping, potentially coexisting with substantial SOTs. Here, we examine the impact of intentional compositional gradients on damping and SOTs, specifically in graded films
consisting of two ferromagnetic elements: Fe with low intrinsic damping [4] and Ni with sizable spin-orbit coupling [5]. We grew 10-nm-thick graded and homogeneous Fe-Ni films by continuously tuning the sputtering powers on Fe and Ni sources [Fig. 1(a-c)]. The targeted vertical compositional and
magnetic gradients are confirmed and quantified by polarized neutron reflectometry. In-plane broadband ferromagnetic resonance (FMR) [Fig. 1(d)] points to low ef ective damping
parameters of ≈0.0045 for the graded films, comparable to ≈0.0038 for the homogenous film. Out-of-plane FMR [Fig. 1(e)] reveals intrinsic damping parameters of ≈0.0032 for both the
graded and homogenous Fe-Ni films. These FMR results indicate that low damping is maintained despite the steep, intentional vertical inhomogeneity. From spin-torque FMR
measurements on a graded sample, we detect a modest (at most ≈2%) linear change in the FMR linewidth with a DC current density of 1×1011 A/m2
[Fig. 2], suggesting a small dampinglike SOT. Our findings constitute a step toward understanding and engineering low-damping single-layer ferromagnetic films for SOT-driven applications. 
**References** [1] Liu, L., Yu, J., Gonzalez-Hernandez, R., Phys Rev. B., Vol. 101, p. 220402 (2020) 
[2] Tang, M., Shen, K., Xu, S., Advanced Materials, Vol. 32, p. 2002607 (2020) 
[3] Zhu, L., Ralph, D. C., & Buhrman, R. A. Advanced Functional Materials p. 2103898 (2021) 
[4] Wu, S., Smith, D.A., Nakarmi, P., et. al., Phys Rev. B., Vol, 105, p. 174408 (2022) 
[5] Du, C., Wang, H., Yang, F., et. al., Phys Rev. B., Vol. 90, p. 140407 (2014) 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/5c298ab0a08d5d203c251d6f15a04437.png) 
Fig. 1: (a,b) Schematics of (a) FeNi graded, (b) NiFe graded, and (c) FeNi homogeneous films. (d,e) Frequency dependence of (d) in-plane and (e) out-of-plane FMR linewidth for homogeneous and graded Fe-Ni films. 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/4fc66015f32a2a8a2709c1a39348e0fb.png) 
Fig. 2: DC bias current dependence of spin-torque FMR linewidth for 10-μm-wide graded NiFe strip at 7 GHz, magnetized at in-plane angle (a) 50o and (b) 230o

Single Layer Vertically Graded Fe

The ability to manipulate the topological spin textures, such as magnetic skyrmions, is one of the crucial requirements in advance spintronics research. Recently, attempts have been made to understand the mechanism of Domain wall (DW) pair to skyrmion conversion in a specially designed nanotrack which may be useful in memory and logic operation [1,2]. Here, using micromagnetic simulation, we investigate the role of geometry in controlling the DW to skyrmion conversion in a three-channel narrow nanotrack adjoined to a wide nanotrack. Dimension of the nanotrack is as follows; length - 800 nm, thickness - 1 nm, width of narrow nanochannel - 20 nm, width of wider nanochannel - 200 nm, with spacing between the three narrow channels (lower -1, middle - 2, and upper - 3) varied symmetrically and asymmetrically from 10 - 30 nm in step of 10 nm. The simulations are performed using a python interfaced OOMMF known as Ubermag, where a Zhang-Li torque evolver in the Landau-Lifshitz-Gilbert equation is incorporated to understand the magnetization dynamics under the influence of spin current [3]. In figure 1, by keeping the separation between narrow channels 1 and 2 as well as 2 and 3 fixed as 10 nm, Gilbert damping α = 0.3 and non-adiabatic torque parameters β = 0.3, conversion of DWs to two skyrmions are shown [4]. Interestingly, we note that while the steady state velocity for both the skyrmions are same, the time scale involved in DW to skyrmion for individual skyrmion varies resulting in difference in the x-position. By increasing the separation between channel 2 and 3 to 30 nm and keeping all other parameters fixed, formation of a skyrmion and a meron is observed in figure 2. We envision that such difference in the observation of topological spin texture by changing the separation between the narrow nanochannels will be useful for implementing futuristic skyrmion-based logic gate devices. 

**References** 
[1] A. Fert, V. Cross, J. Sampaio Nature Nanotech., Vol. 8, p. 152, (2013). 
[2] Y. Zhou, M. Ezawa, Nat. Commun., Vol. 5, p. 4652, (2014). 
[3] M. Beg, M. Lang, H. Fangohr., IEEE Trans. Magn. Vol. 58, p. 1-5 (2021) 
[4] P. Hari Prasanth, Syamlal S K, B. Priyanka, J. Sinha, Manuscript under preparation. 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/d1d0c5f3d1bfa99da4e93dfe7637c1cd.png) 
Fig 1: Snapshot of DW to skyrmion conversion from the three symmetrically separated narrow nano-channels for α = β = 0.3 and separation - 10 nm. 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/f37168fd86d14542429e1d5a3a107039.png) 

Fig 2: From asymmetrically separated narrow nano-channels (separation between 1 and 2 - 10 nm and between 2 and 3 - 30 nm) and for α = β = 0.3 conversion of DWs into a skyrmion and a meron.

Controlled skyrmion creation from a Domain wall pair for logic gate applications

Magnetic skyrmions [1] are magnetic quasi-particles with interesting properties for possible future applications in efficient low-power neuromorphic computing concepts. Thermally excited skyrmions in confined geometries, as necessary for device applications, have been shown to arrange based on commensurability effects [2]. Here, we investigate the enhanced dynamics and altered equilibrium state of a system in which the intrinsic skyrmion-skyrmion and skyrmion-boundary interaction compete with spin-orbit torques (SOTs) due applied currents [3]. In particular, we employ particle-based simulations to study four skyrmions in a triangular confinement, while injecting spin-polarized currents between two corners of the structure [4]. To analyze the observed positions of the skyrmion ensemble, we coarse-grain the skyrmion states in the system. In the context of neuromorphic computing, such coarse-graining may be key to identify the most suitable positions for potential readouts as well as to understand the collective skyrmion dynamics in systems with competing interactions at different scales. 
**References** 
[1] K. Everschor-Sitte et al., Journal of Applied Physics 124, 240901 (2018) 
[2] C. Song et al., Adv. Funct. Mater. 31, 2010739 (2021) 
[3] K. Raab et al., arxiv:2204.14720 (2022) 
[4] T. Winkler et al., in preparation (2022)

Analyzing collective thermal Skyrmion Dynamics by coarse graining

Magnetic refrigeration is a sustainable, energy-efficient alternative to the conventional vapor-compression cooling technology. A key challenge in manufacturing magnetocaloric devices is that lack of fabrication methods for shaping the brittle caloric alloys into thin-walled channeled regenerator structures with optimized heat transfer properties, and gradient transformation temperature, while preserving the functional response of the materials system, Fig 1.1 To this end, we have recently developed a novel extrusion-based additive manufacturing (AM) method to 3D print spatially designed porous magnetocaloric structures with channel dimensions in the range 150-800 Âµm, Fig 2.1 Building on this proof-of-concept demonstration, research efforts pertaining to AM process development using three precursor magnetocaloric powders will be presented - (1) La0.6Ca0.4MnO3 nanoparticles (dia~10 nm) prepared by Pechiniuidelines for minimizing porosity and lack-of-fusion defects in the 3D printed magnetocaloric parts.

Influence of Powder Feedstock Characteristics and Process Parameters on Extrusion based 3D Printing of Magnetocaloric Structures

Materials used in spintronics and spin caloritronics, such as thin film ferrimagnetic yttrium iron garnet (YIG), are often grown on bulk substrates, such as gadolinium
gallium garnet (GGG), due to their exceptional lattice matching and disordered magnetism.1 Magnetometry measurements can resolve YIG thin films down to a few nanometers, but
assuming a linear paramagnetic background when accounting for the GGG substrate can contribute significant artifacts in the resulting signal.2 Superconducting magnet coils are
susceptible to trapped flux, leading to measurements performed in the their fields to require precise calibration of the resulting magnetic field, particularly on films with small coercivites or
grown on substrates with large paramagnetic susceptibilities. Using a 20nm YIG thin film grown on GGG as an example, we show that performing a simple linear paramagnetic
background subtraction can produce artifacts, including negative remanence, vertical exchange bias, and shifts along the field axis. We demonstrate that direct measurements of standalone
substrates in carefully reproduced field conditions and field correcting with a standard reference are two ways to minimize the inclusion of these magnetic artifacts in quantitative
magnetometry measurements. 

**References:** 

[1] H. Chang, P. Li, W. Zhang, T. Liu, A. Hoffmann, L. Deng, and M. Wu, Nanometer-thick yttrium iron garnet films with extremely low damping. IEEE Magn. Lett. 5, 1
(2014) 
[2] Roos, M. J., Quarterman, P., Ding, J., Wu, M., Kirby, B. J., & Zink, B. L.. Magnetization and antiferromagnetic coupling of the interface between a 20 nm Y3Fe5O12film and
Gd3Ga5O12 substrate. Physical Review Materials, 6(3), 034401 (2022) 

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