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[Manuscript.pdf](https://mdr.nims.go.jp/filesets/d1f25dc2-c371-41e0-ab92-0dc550a25004/download)

## Creator

[Xiao Wang](https://orcid.org/0000-0001-8139-4192), [Jie Zhang](https://orcid.org/0009-0006-9055-2969), [Zhao Pan](https://orcid.org/0000-0002-8693-2508), [Dabiao Lu](https://orcid.org/0009-0006-5489-2835), Maocai Pi, [Xubin Ye](https://orcid.org/0000-0002-5739-8318), Cheng Dong, [Jie Chen](https://orcid.org/0000-0001-9609-669X), Kai Chen, Florin Radu, Sonia Francoual, [Stefano Agrestini](https://orcid.org/0000-0002-3625-880X), [Zhiwei Hu](https://orcid.org/0000-0003-0324-2227), Chun-Fu Chang, Arata Tanaka, [Kazunari Yamaura](https://orcid.org/0000-0003-0390-8244), Yao Shen, [Youwen Long](https://orcid.org/0000-0002-8587-7818)

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This document is the Accepted Manuscript version of a Published Work that appeared in final form in The Journal of Physical Chemistry C, copyright © 2024 American Chemical Society  after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acs.jpcc.4c04491[In Copyright](http://rightsstatements.org/vocab/InC/1.0/)

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[X-ray Absorption Spectroscopic Study of the Transition-Metal-Only Double Perovskite Oxide Mn<sub>2</sub>CoReO<sub>6</sub>](https://mdr.nims.go.jp/datasets/de85bd79-4b02-4d02-8a7f-5c7a02baae7d)

## Fulltext

1  X-Ray Absorption Spectroscopic Study of the Transition-Metal-Only Double Perovskite Oxide Mn2CoReO6 Xiao Wang,1,* Jie Zhang,1,2 Zhao Pan,1 Dabiao Lu,1,2 Maocai Pi,1,2 Xubin Ye,1 Cheng Dong,1 Jie Chen,3 Kai Chen,4 Florin Radu,5 Sonia Francoual,6 Stefano Agrestini,7 Zhiwei Hu,8 Chun-Fu Chang,8 Arata Tanaka,9 Kazunari Yamaura,10,11 Yao Shen,1,2,** and Youwen Long1,2,12,***  1Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China 2School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China 3Laboratory for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama, Kanagawa 226–8503, Japan 4National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230026, China 5Helmholtz-Zentrum Berlin fur Materialien und Energie, Albert-Einstein-Str.15, 12489 Berlin, Germany 6Deutsches Elektronen-Synchrotron (DESY), Notkestraße 85, 22607 Hamburg, Germany 7Diamond Light Source, Didcot, United Kingdom 8Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany 9Quantum Matter Program, Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-hiroshima 739-8530, Japan. 10Research Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki, 305-0044, Japan 11Graduate School of Chemical Sciences and Engineering, Hokkaido University, North 10 West 8, Kita-ku, Sapporo, Hokkaido, 060-0810, Japan 12Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China *wangxiao@iphy.ac.cn **yshen@iphy.ac.cn ***ywlong@iphy.ac.cn    2  Abstract By means of x-ray absorption spectroscopic studies, both experimentally and theoretically, we investigated the magnetic properties of the transition-metal-only double perovskite oxide Mn2CoReO6, which experiences an antiferromagnetic transition at TN = 93 K whereas holds a considerable net moment at low temperature. Internal magnetic fields against the applied magnetic field for all the transition metal ions were identified, providing a microscopic insight of the intra-site antiferromagnetic couplings. Nevertheless, parallelly oriented canted spins of the Mn, Co and Re cations were observed. In particularly, the Mn and Co cations hold considerable canting moments, which can be ascribed to the competition between the ferromagnetic inter-site and antiferromagnetic intra-site magnetic interactions. Moreover, a linear magnetoresistance effect was observed below TN. The concurrence of the magnetoresistance effect and the antiferromagnetic nature make Mn2CoReO6 a promising candidate for high-speed and energy-saving spintronics applications.  Introduction The realization and utilization of both charge and spin degrees of freedom of the electrons underpins spintronics.1–3 Reported spin-dependent electron transport mechanisms are giant magnetoresistance (GMR) in trilayer heterostructures with a nonmagnetic spacer sandwiched by two ferromagnetic (FM) electrodes,4 tunnel magnetoresistance (TMR)5 in magnetic tunnel junctions (MTJs), and magnetic random access memories (MRAMs).6  Antiferromagnetic (AFM) spintronics has attracted intense attention owing to its fast dynamics with frequency up to terahertz.7 However, the zero net moment of the AFM materials severely impedes the manipulation of the magnetization, leaving great challenges in applications. Nevertheless, multiple spin dependent phenomena have been discovered in AFM materials that can encode and transport information through such as magnetoresistance (MR),8 magnetoelectric multiferroics,9 anomalous Hall effect,10 spin torque,11 magneto-optical Kerr effect,12 etc. Therefore, AFM materials hold great opportunities for both academic studies and functional applications.  Double perovskite oxides with a formula of A2BBʹO6 can flexibly accommodate different types of ions at the A, B and Bʹ sites, making them attractive for engineering and studying potentially new spintronic materials. For example, the up-spin channel of Sr2FeMoO6 opens up a gap while the down-spin channel is conductive, making it a half metal with 100% spin polarization 3  and exhibiting GMR.13,14 Similar half metallic behavior combined with GMR is also observed in double perovskite Sr2FeReO6.15 Sr2CrOsO6 has a super high TC of 725 K as a result of the robust AFM coupling between the Cr and Os ions at the B and B' sites, respectively.16 Y2NiIrO6 exhibits giant exchange bias attributable to the pinned magnetic domains due to the combination of strong spin-orbit coupling of the Ir ions and the AFM coupling of the Ni and Ir sublattices.17 In most cases, the A site of double perovskites host nonmagnetic ions such as alkali, alkali earth and lanthanides. Recent studies have shown that transition metals can also occupy the A site, resulting in novel magnetic and electronic interactions through the A-B and A-Bʹ pathways, further leading to intriguing properties for the transition-metal-only double perovskite oxides such as half metallicity,18 GMR,19 cation rattling,20 and multiferroicity.21  Nevertheless, the studies on transition-metal-only double perovskite oxides are still limited. The small transition metal at the A site leads to a significant mismatch between the A and B sites, resulting in significant tilt of the BO6 octahedra. To the best of our knowledge, the few reported transition-metal-only double perovskites are prepared under high pressure over 5 GPa.18–23 Mn2CoReO6 (MCRO) is the fourth known transition-metal-only double perovskite oxides.23 It experiences an antiferromagnetic transition at TN = 93 K nevertheless possesses a considerable net moment at low temperature. In this paper, by experimental and theoretic x-ray absorption spectroscopic studies, together with multiple measurements, we obtained a negative internal magnetic field for all the three transition metal cations, indicating the dominant AFM intra-site magnetic couplings. However, parallel canting spins of Mn, Co and Re are identified. In particularly, the Mn and Co cations hold considerable canting moments, which can be ascribed to the competition between the intra- and inter-sites magnetic interactions between them. On the other hand, a linear MR effect was observed below TN. Therefore, MCRO holds basic traits that are relevant to future high-speed and energy-saving AFM spintronics applications.  Methods Polycrystalline MCRO was synthesized under high-pressure and high-temperature (HPHT) conditions. Stoichiometric high purity (> 99.9%) starting materials MnO, CoO and ReO3 were thoroughly ground with an agate mortar in argon gas atmosphere. Then the mixed powder was pressed into a platinum capsule of 3 mm diameter and 4 mm height and then treated with an anvil-type high-pressure apparatus under 9 GPa and 1523 K for 30 minutes. After the HPHT treatment 4  the temperature was quenched to room temperature in seconds and the pressure was slowly released to ambient in several hours.  The synchrotron x-ray diffraction (SXRD) patterns were collected at the BL02B2 (λ = 0.65 Å) beam line of SPring-8 in Hyogo. The 2θ scan was performed from 2° to 70° with a step of 0.006°. The Rietveld refinement of crystallographic parameters was performed using the GSAS software pakage.24 The magnetic susceptibility and magnetization were measured using a Quantum Design superconducting quantum interference device magnetometer (MPMS-3). Both zero-field-cooling (ZFC) and field-cooling (FC) modes were adopted for magnetic susceptibility measurements with a 0.1 T magnetic field. The resistivity was measured using a sample pellet with the size of about 2 × 1 × 1 mm3 by a standard four-probe method on a Quantum Design physical property measurement system (PPMS-7). The heat capacity was measured using a sample pellet of size about 2 × 2 × 0.4 mm3 on PPMS-7.  The Mn-L2,3 and Co-L2,3 x-ray absorption spectroscopy (XAS) were measured at room temperature via total electron yield (TEY) mode at TPS 45A beamline of National Synchrotron Radiation Research Center (NSRRC) in Hsinchu. The Mn-L2,3 and Co-L2,3 x-ray magnetic circular dichroism (XMCD) were measured at 10 K and 8 T using TEY mode at the VEKMAG end station25 at the HZB/BESSY II synchrotron radiation facility in Berlin. The XAS and XMCD at the Re-L2,3 edges were measured in transmission at beamline P09 at PETRA III at DESY in Hamburg, and the Re-L2,3 XMCD was measured at 10 K and 5 T. For the XMCD measurements, both the magnetic field and the polarization (~77% for VEKMAG and ~99% for P09) of the light were flipped to obtain the μ+ (parallel) and μ− (antiparallel) spectra.  Results & Discussion Figure 1 displays the SXRD pattern of MCRO, which can be refined with the space group P21/n (No. 14) with lattice parameters a = 5.23506(1) Å, b = 5.35179(1) Å, c = 7.63109(2) Å, and β = 89.966(0)°. The crystal structure was depicted in the inset at the right side of Figure 1. As shown in Figure 1 and the inset in the middle, the (011) diffraction peak clearly indicates the rocksalt-type distribution of Co and Re at the B and Bʹ sites, respectively.26 A slight anti-site occupancy of 2% between the Co and Re was found. A previous neutron powder diffraction (NPD) also indicated ~16% disorder between A-site Mn and B-site Co.23 The detailed refined parameters from SXRD are listed in Table S1. The valence states of Mn2+ and Co2+ can be obtained via the bond valence 5  sum (BVS)27 calculations based on the refined bond lengths (Table S2). For Re, the averaged Re-O bond length is 1.920 Å, very close to that of Sr2MgRe6+O6 (1.912 Å),28 indicating a Re6+ state for MCRO.  Figure 1. SXRD pattern and Rietveld refinement of MCRO. The black circles, red lines and blue lines indicate the observed, calculated and difference, respectively. The magenta ticks indicate the allowed Bragg reflections for space group P21/n. The inset in the middle displays the SXRD pattern near the (011) diffraction peaks. The inset at the right side displays the crystal structure of MCRO. Mn, Co, Re and O are shown in purple, blue, grey and red, respectively.   In order to directly obtain the valence states of the cations in MCRO, we performed XAS measurements. It is well known that the XAS is an element selective technique highly sensitive to the valence state. For an open d shell system, an increase of the valence of the transition metal ion by one leads to a shift of the L2,3 XAS spectrum to higher energies by one electron volt (eV) or more that is also accompanied by remarkable changes of the spectral feature.29–31 As shown in Figure 2a, the white line of the Mn-L2,3 XAS of MCRO resembles that of Mn2+ reference compound MnO with the L2/L3 peak locating at the same energy as that of MnO, which points to the occurrence of a Mn2+ valence state. Similarly, as shown in Figures 2b and 2c, the peak energies and the shape of the white lines of the Co-L2,3 and Re-L3 XAS respectively resemble that of the high-spin Co2+ and Re6+ references,32 indicating the occurrence of high spin Co2+ (t2g5eg2) and Re6+ valence states. Therefore, the valence configuration Mn2+/Co2+/Re6+ is experimentally validated. 6   Figure 2. XAS at the (a) Mn-L2,3, (b) Co-L2,3, and (c) Re-L3 edges of MCRO. The XAS of MnO, CoO and Sr2MgReO6 are displayed as Mn2+, Co2+ and Re6+ references, respectively.  After the determination of the structure and the valence states, we continue with the description of the magnetic properties of MCRO. Figure 3a displays the temperature-dependent magnetic susceptibility of MCRO. At TN = 93 K, an AFM transition can be clearly identified. An NPD study has demonstrated that this AFM transition is related to the antiparallel spin alignment of all of the Mn, Co, and Re sublattices.23 It is worth noting that the AFM transition is relatively broad in temperature, as an implication of competing FM and AFM coupling mechanisms. Moreover, the ZFC and FC curves start to separate below TN (see inset of Figure 3a) and further 7  split with temperature decreasing, indicating the formation of a canted AFM structure. As shown in Figure 3b, the Curie-Weiss fitting was performed above 180 K with the function χ−1 = (T − θ)/C. The positive Weiss temperature θ = 50 K indicates the presence of FM interactions in Mn2CoReO6. According to the fitted Curie constant, C = 8.18 emu K mol−1 Oe−1, the effective magnetic moment is calculated to be µexp = 8.09 (√8𝐶𝐶) Bohr magnetons per formula unit (µB/f.u.), slightly smaller than the spin-only theoretical value of 9.38 µB/f.u. (g�∑ 𝑆𝑆𝑖𝑖(𝑆𝑆𝑖𝑖 + 1)𝑖𝑖 , where g = 2 is the Landé factor of spins), considering Mn2+ (S = 5/2), Co2+ (S = 3/2, high-spin), and Re6+ (S = 1/2) ions. The smaller experimental value can be a result of a reduction of Re6+ moment through the spin-orbit coupling. Figure 3c displays the isothermal field-dependent magnetization of MCRO. At temperatures above TN, the magnetization is linearly dependent on the magnetic field, in agreement with a paramagnetic state. When temperature further decreases down to 2 K, a prominent hysteresis and a moment of 1.1 µB/f.u. at 7 T can be found, which is indicative of the competition between the AFM and FM couplings which will be discussed later. 8   Figure 3. (a) Temperature dependent magnetic susceptibility of MCRO. The inset displays the region near TN = 93 K. (b) The inversed magnetic susceptibility (black circles) and the Curie-Weiss fitting above 180 K with formula χ−1 = (T − θ)/C. (c) Field dependent magnetization of MCRO at selected temperatures.  We further measured the heat capacity of MCRO. As shown in Figure 4a, a cusp feature emerges at TN, in agreement with the AFM transition. It is worth noting that this feature is relatively weak, quite different from the sharp peak expected at AFM transitions.33 In order to display the ingredients that contribute to the heat capacity, we plotted the CP/T-T2 plot below 10 K, as depicted in Figure 4b. The convex curve at low temperature clearly indicates the magnetic contribution on the specific heat, in accord with the concurrence of both magnetic and antiferromagnet interactions 9  in MCRO. The heat capacity can be well fitted with formula CP/T = αT2 + βT1/2 + γ, with α = 1.53 mJ mol−1 K−4, β = 23.5 mJ mol−1 K−5/2, and γ = 4.24 mJ mol−1 K−2, indicating that the phonons, magnons and electrons all contribute to the heat capacity, in agreement with the canted AFM semiconductive nature of MCRO.  Figure 4. (a) Temperature dependent heat capacity of MCRO. (b) Experimental heat capacity below 10 K (black circles) and the fitting with formula CP/T = αT2 + βT1/2 + γ (red line).  In order to obtain a deeper insight of the configuration of the canted spins, we performed XMCD measurements on the Mn, Co and Re ions. It is known that the element-selective XMCD is a sensitive probe for determining the spin alignment of the magnetic ions.32,34,35 As shown in Figure 5, the XMCD signal at the L3 (L2) edge of all transition metals is negative (positive), demonstrating that the resultant spins direction of Mn, Co and Re are parallel to each other in an applied magnetic field.36,37 Herein, MCRO provides a very rare example in double perovskite with parallel spins at all A, B, and Bʹ sites. Usually, the superexchange coupling between the 5d and 3d ions through the A/B-O-Bʹ pathway as well as a two sublattice double-exchange mechanism38 can lead to the magnetic property. For example, in Sr2FeReO6, Sr2CrOsO6 and Y2NiIrO6, the B-site 3d 10  and Bʹ-site 5d ions are ferrimagnetically (FiM) coupled.15–17 Similar FiM structures can be also found in the quadruple perovskite oxides CaCu3Fe2Bʹ2O12 (Bʹ = Re and Os).39–41   Figure 5. XMCD spectra at the (a) Mn-L2,3, (b) Co-L2,3, and (c) Re-L2,3 edges of MCRO. The XAS with light polarization parallel (μ+, black lines) and antiparallel (μ−, red lines) to the magnetic field are shown. The blue lines are the XMCD (μ+ − μ−) spectra. The dashed lines indicate the edge jump.  One can observe that the XMCD signal for all the three cations Mn, Co and Re are much smaller than the typical ferromagnets,42,43 as the net magnetization is from canted spins. In order to obtain an inner view of the magnetic moments of the cations, we performed full-atomic-multiplet ligand-field calculations using the XTLS code.44 This theoretic calculation includes the full intra-atomic multiplet interactions, the atomic d spin-orbit coupling (SOC), the transition metal d to O-2p hybridization, and the crystal field interaction. This model has very successfully 11  reproduced the line shape of XMCD spectra of transition metal element in the past decades.45,46 The parameters are listed in Ref. 47. The calculations well reproduce the measured spectra, as shown in Figure 6. In our calculations, in order to obtain the intensity of the XMCD signal, negative exchange fields (Hex) were adopted for all the three transition metal ions Mn2+, Co2+ and Re6+.47 The negative Hex is indicative of an internal magnetic field against with the applied field. These results provide a microscopic insight of the intra-site AFM couplings of the Mn, Co and Re sublattices.  Figure 6. Calculated XMCD spectra at the (a) Mn-L2,3, (b) Co-L2,3, and (c) Re-L2,3 edges of MCRO. The XAS with light polarization parallel (μ+, black lines) and antiparallel (μ−, red lines) to the magnetic field are shown. The blue lines are the XMCD (μ+ − μ−) spectra.  12  From the cluster calculation, the spin and orbital moments of Mn, Co and Re are listed in Table 1. A total moment of 1.83 μB/f.u. is obtained. The larger moment than the magnetization measurements (Figure 3c) could be a result of the stronger applied magnetic field for the XMCD measurements. One can also find considerable spin moments of Mn and Co, indicating that the spins of Mn and Co are notably canted along the applied magnetic field. Note that the orbital moment of Mn2+ is negligible because of the half-filled 3d orbit (t2g3↑eg2↑). On the contrary, the spin moment of Re is very small, indicating that the AFM alignment of the Re spins almost maintain.  Table 1. Spin and orbital moments from calculations.   Mspin  Morb  Mn (μB/atom) 0.471 / Co (μB/atom) 0.638 0.251 Re (μB/atom) 0.0159 −0.0144 Total (μB/f.u.) 1.83 μB/f.u.   In order to understand the different canting behavior between Mn/Co and Re sites, we discuss the possible magnetic interactions in MCRO. The intra-site AFM structure is indicative of the dominate long-range superexchange pathway M-O-Mʹ-O-M, as a consequence of the energy differences of the orbitals between the M and Mʹ ions.48,49 Here in MCRO, different orbitals of 3d-eg, 3d-t2g and 5d-t2g for Mn2+ (3d5), Co2+ (3d7) and Re6+ (5d1), respectively, are involved in the magnetic couplings, giving rise of the domination of the long-range superexchange couplings. On the other hand, the canted moments of MCRO indicate the competition of magnetic interactions against the long-range superexchange one. Here we consider the superexhange pathway M-O-Mʹ. As shown in Figure 7 and Table S3, the bond angle(s) ∠Mn-O-Co and ∠Mn-O-Re are close to 90°, and ∠Co-O-Re is close to 180°. According to the Goodenough-Kanamori-Anderson rules,50–52 the B-site Co is FM coupled with both the A-site Mn and Bʹ-site Re ions, and Mn and Re are AFM coupled. On account of the localized 3d orbit, the FM inter-site superexcharge interaction between Mn and Co is supposed to play a role thus competes with the AFM intra-site couplings. It therefore explains that Co and Mn hold considerable canted spins whereas the spin of Re almost maintains the antiparallel alignment as listed in Table 1.  13   Figure 7. The bond angles of (a) Mn-O-Re, (b) Mn-O-Co and (c) Co-O-Re. The Mn, Co and Re ions are shown in purple, blue and grey, respectively. The different O sites are shown in red, orange and brown, respectively.  We further investigated the transport properties of MCRO. As shown in Figure 8a, the electrical resistivity increases with cooling, exceeding the measuring range (106 Ω cm) below 80 K, indicating either a semiconductive or an insulative behavior. The temperature dependent electrical resistivity can be well fitted with the thermal activation model within the temperature range 260–350 K with the formula ρ = ρ0 × exp(Ea/kBT), where ρ0 and Ea representing the residual resistance and the activation energy, respectively, and kB is the Boltzmann constant. This demonstrates that MCRO is a semiconductor. The obtained energy gap from the fitting is Ek = 2Ea = 0.29 eV, and the residual resistance is 0.11 Ω cm.  14   Figure 8. (a) Temperature dependent resistivity of MCRO. The inset displays the experimental data (black circles) and the thermal activation model fitting with formula ρ = ρ0 × exp(Ea/kBT) in the temperature range 260–350 K. (b) Field dependent magnetoresistance of MCRO at 150 K and 80 K. The inset depicts the region of ±2 T.  The canted AFM structure with a considerable net magnetic moment allow MCRO to be utilized as high-speed spin filtering by means of the TMR mechanism through magnetic domains and grain boundaries of polycrystalline MCRO.5,14 As displayed in Figure 8b, at 150 K (> TN), the MR of MCRO is almost independent of the magnetic field, in agreement with a paramagnetic state. Note that the slight decrease of MR is caused by some extrinsic effects such as short-range magnetic correlations. On the other hand, at 80 K (< TN), the MR increases to positive values under small magnetic field and then decreases to negative values upon further magnetic field increase, and is accompanied by a prominent coercivity. This butterfly-shaped MR is reminiscent of the spin-valve-type transport mechanism, which is in accordance with the tunnel effect between multi-layer junctions and/or grain boundaries.13,14,53,54 The MR reaches 8% at 80 K and 7 T, and depends linearly on the applied magnetic field above 2 T. Note that the electrical resistivity exceeds the 15  measuring range below 80 K. To take into consideration of the large coercivity at 2 K which can lead to a strong pining effect of the spins,17 we thus speculate a much larger TMR at lower temperatures for a more conductive MCRO sample through disordering, doping, and/or oxygen vacancies.  Conclusions In summary, the transition-metal-only double perovskite oxide Mn2CoReO6 was studied by element-selective x-ray absorption spectroscopy. The valence states of Mn2+/Co2+/Re6+ were experimentally determined. An internal magnetic field against with the applied magnetic field was obtained, providing a microscopic insight of the intra-site antiferromagnetic couplings. Nevertheless, x-ray magnetic circular dichroic measurements manifest that all the Mn, Co and Re spins are canted and parallel with each other, and particularly, the 3d Mn and Co cations hold considerable canting moments, which can be ascribed to the competition between the intra- and inter-sites magnetic interactions. Moreover, a linear magnetoresistance effect was observed below TN, which is resulted from the spin-valve-type tunneling through the grain boundaries. The concurrence of the antiferromagnetic nature as well as the linear magnetoresistance effect make Mn2CoReO6 a promising candidate for high-speed and energy-saving spintronics applications.  Supporting Information Detailed lattice parameters, bond lengths and bond angles from SXRD refinement   Acknowledgements This work was supported by the National Key R&D Program of China (Grant No. 2021YFA1400300), the National Natural Science Foundation of China (Grants No. 11934017, 12261131499, 11921004, 12304159, 12304268), the Beijing Natural Science Foundation (Grant No. Z200007), and the Chinese Academy of Sciences (Grant No. XDB33000000). The synchrotron x-ray diffraction experiments were performed at SPring-8 with the approval of the Japan Synchrotron Radiation Research Institute (2023B1575). The authors thank DESY (Hamburg, Germany), a member of the Helmholtz Association HGF, for the provision of experimental facilities. Parts of this research were carried out at beamline P09 at PETRA III under proposal I-20200812. The 6T/2T/2T used for the XMCD measurements at P09 was funded in part by the 16  BMBF grant No. 05K2013 from the German Federal Ministry of Education and Research. The authors thank J. Linares Mardegan and Olaf Leupold for scientific and technical support at P09. Financial support for developing and building the PM2-VEKMAG beamline and VEKMAG end-station was provided by HZB and BMBF (Grant Nos. 05K10PC2, 05K10WR1, and 05K10KE1). The research in Dresden was partially supported by the DFG through SFB 1143. The authors acknowledge the support from the Max Planck-POSTECH-Hsinchu Center for Complex Phase Materials.  Notes The authors declare no competing financial interest.  References 1 Fert, A. Nobel lecture: origin, development, and future of spintronics. Rev. Mod. Phys. 2008, 80, 1517–1530. 2 Bibes, M.; Villegas, J. E.; Barthélémy, A. Ultrathin oxide films and interfaces for electronics and spintronics. Adv. Phys. 2011, 60, 5–84. 3 Fusil, S.; Garcia, V.; Barthélémy, A.; Bibes, M. Magnetoelectric devices for spintronics. Annu. Rev. Mater. Res. 2014, 44, 91–116. 4 Baibich, M. N.; Broto, J. 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