Opening

• 欣 童 (高能所)

The Status of CSNS

• Sheng 王生 (高能所)

Studies of the centrosymmetric skyrmion materials using polarized neutron scattering

• Taro Nakajima (ISSP University of Tokyo)

Topologically nontrivial magnetic orders have attracted remarkable attention since the discovery of magnetic skyrmions in MnSi [1]. The term “magnetic skyrmion” originally refers to a particle-like swirling spin object in a magnetic material. However, it often appears in a form of periodic lattice, which is regarded as a long-range magnetic order described by multiple magnetic modulation wave vectors (q-vectors), namely, a multi-q magnetic order. Neutron diffraction is one of the most powerful techniques to study the periodically modulated magnetic structures including the skyrmion lattices (SkLs). In this talk, we will introduce our neutron scattering studies on the centrosymmetric skyrmion-host materials, Gd2PdSi3[2], EuAl4 [3]. In the early studies of magnetic skyrmions, ferromagnets with non-centrosymmetric crystal structure were considered to be the most promising candidates for skyrmion-host materials since competitions between Dzyaloshinskii-Moriya (DM) and ferromagnetic interactions can induce long-period modulated magnetic structures. However, subsequent studies demonstrated that SkLs can also be realized in centrosymmetric magnets, in which long-range interactions arising from couplings between conduction electrons and localized magnetic moments play essential roles. Gd2PdSi3 is one of the centrosymmetric skyrmion hosts and exhibits a large topological Hall effect in the first-field-induced phase [4]. The magnetic structures of this system were first studied by resonant x-ray magnetic scattering [4]. We further investigated the temperature dependence of the magnetic structure by polarized neutron scattering at PONTA spectrometer in JRR-3 [2]. Another example is EuAl4, which shows a variety of magnetic orders depending on temperature and magnetic field. To identify these magnetic phases, we performed polarized neutron scattering at PONTA and TAIKAN(BL15) in Materials and Life-science experimental Facility of J-PARC, revealing two distinct SkL phases in in this compound [3]. In this talk, we also briefly introduce our recent attempt to combine the polarized neutron scattering technique with pulsed high magnetic fields. References [1] S. Muhlbauer et al., Science 323, 915 (2009). [2] J. Ju et al., Phys. Rev. B 107, 024405 (2023). [3] R. Takagi et al., Nat. Commun. 13, 1472 (2022). [4] T. Kurumaji et al., Science 365, 914 (2019).

Polarised neutrons for European Spallation Source users (Download the latest program here)

• Wai Tung Lee (European Spallation Source ERIC)

Polarised neutrons have long been used in reflectometry, diffraction and inelastic scattering to study magnetic structures and dynamics in nano- to meso-scales [1]. Polarisation analysis also provide a complementary tool to deuteration in the determination of coherent and single-particle motions in soft matter studies [2,3], in imaging to quantitatively studying magnetic domain evolution in microscopic scale [4,5]. In fundamental physics, the search for the neutron electric dipole moment and the study of symmetry violation are two of the many examples that use polarised neutrons. Owing to the persistent push to advance the technology, polarised neutron has changed from a scarce resource that often requires an instrumentation expert to carry out measurements, to becoming a commonly available resource that can benefit a considerably wider research community. To date, 40% of instruments are providing polarised neutron capability. To meet the coming user demand, twelve of the fifteen ESS instruments [6] under construction aim to offer polarised neutrons for user experiments. They include an imaging instrument (ODIN), a SANS instrument (SKADI), two reflectometers (ESTIA, FREIA), three diffractometers (DREAM, HEIMDAL, MAGiC), and four spectrometers (BIFROST, CSPEC, MIRACLES, T-REX). In conjunction with in-kind contributions and instrument grants, the ESS Polarisation Project will support eight of the eleven instruments to incorporate polarisation analysis capabilities [7]. Neutron spin filters based on polarised 3He technologies - Metastable Optical Pumping and Spin Exchange Optical Pumping, and polarising supermirror devices are selected according to the different neutronic requirements and constraints on each instrument. An update of the project will be presented with highlights on some of the instrumentation innovations and improvements, alongside examples on the use of polarised neutrons in material studies. [1] Chatterji, Tapan, ed. Neutron scattering from magnetic materials. Elsevier, 2005. [2] A. Arbe, et. al., Phys. Rev. Research **2**, 022015(R) (2020). [3] A. Arbe, et. al., J. Chem. Phys. **158**, 184502 (2023). [4] A. Backs, et. al., EPJ Web of Conferences **286**, 05003 (2023). [5] M. Strobl, et. al., J. Phys. D: Appl. Phys. **52** 123001 (2019). [6] K. Andersen, et. al., Nucl. Instrum. Methods **A 957**, 164302 (2020). [7] W.T. Lee et. al., EPJ Web Conf. **286** 03004 (2023). E-mail of the corresponding author: waitung.lee@ess.eu

Advancing Applied Magnetics: The Role of Neutron Transmission Spectroscopy

• Hiroaki Mamiya

Advanced magnetic systems for neutron instrumentation (Download the latest program here)

• Earl Babcock (Juelich Centre for Neutron Science)

Polarized neutron experiments are an important of the scientific motivation for large scale neutron sources. These experiments often involve the use both the highest available fields and at other times techniques or instrumentation that are highly sensitive to changing magnetic fields or field gradients. This can lead to reduced polarized neutron instrument performance and undesired cross talk between instruments. 3He spin-filter systems at times need to be compatible with operation in the vicinity of high field magnets, such at the 8T magnet for POLI. Hot polarized neutrons must be adiabatically transported for both high field applications and 0-field cryopol applications. Neutron spin-echo should be stable and independent of interference from nearby instruments. Wide angle polarization analysis should be robust, i.e. in the case wide angle 3He spin-filters, or for large area guide fields. This presentation will focus on the developments and concepts for magnetic systems at the JCNS to enable robust polarized neutron instrumentation.

First Measurement of Neutron Birefringence in Polarized ¹²⁹Xe and ¹³¹Xe Nuclei

• Earl Babcock (Juelich Centre for Neutron Science)

New diffraction instrumentation at the second target station at lSlS: the polarisation upgrade on the WISH beamline and WSH-II

• Pascal Manuel

Spin-contrast-variation SANS study of nano-ice crystals in frozen sugar solutions

• Kumada.takayuki

Measuring the Angular Momentum of a Neutron Using Earth’s Rotation (Download the latest program here)

• Niels Geerits (TU Wien)

The Angular Momentum (AM) of a quantum particle is defined as the sum of an intrinsic part, called spin and an extrinsic or structural part known as Orbital Angular Momentum (OAM). For neutrons OAM is a unique quantum mechanical degree of freedom, as OAM is discrete and can take on any integer value. This means OAM could be used as a qudit, which is thought to have a far wider range of application than standard qubits in quantum information [1]. In addition, various authors suggest that twisted waves have different scattering properties, suggesting that twisted neutrons may be useful for nuclear physics [2,3]. Up until the last decade OAM was mostly neglected in neutron optics. In 2015 a first attempt was made to generate neutron OAM in a perfect crystal interferometer [4]. However, only in 2022 were the first helical neutron waves produced on the tail end of the cold spectrum [5]. Nonetheless, many challenges remain, such as efficiently generating OAM on the thermal/cold peak and efficient detection of OAM. In this talk we discuss our work which attempts to address the latter issue [6]. It is well known that the laws of nature appear to work differently in non-inertial frames. An example of such is the apparent coupling between the AM of a test particle and the rotation rate of the frame of reference in which it is observed. This is known as the Sagnac effect [7]. We present and discuss an experiment where the Sagnac effect, arising due to Earths rotation, is used to detect the OAM difference between two path states in a Spin-Echo interferometer. Finally, we argue, that the discrete/quantum Sagnac effect may be detected in our setup by speeding up the rate of rotation, by means of a neutron optical dove prism. [1] T. Giordani et al., PRL 122, 020503 (2019). [2] A.V. Afanasev et al., Phys. Rev. C, 103, 054612 (2021). [3] T. Jach and J. Vinson, Phys. Rev. C, 105, L061601 (2022). [4] C.W. Clark et al., Nature, 525, 504 (2015). [5] D. Sarenac et al., Sci. Adv., 8, eadd2002 (2022). [6] N. Geerits et al., arXiv:2407.09307 (2024). [7] M.G. Sagnac, Comptes Rendus, 157, 708 (1913).

Polarized neutron reflectometry at CSNS and its application to the study of the magnetic thin films

• Tao Zhu

Spin-depth profile studies in Co/Pt multilayers with All-Optical Switching by Polarized Neutron Reflectometry (Download the latest program here)

• Jose Maria Porro Azpiazu (BCMaterials)

All-Optical Switching (AOS) is a phenomenon which is currently attracting significant attention due to its potential applications in magnetic memory storage technologies. The grand advantages against other storage solutions are its high energy efficiency and ultrafast magnetic dynamics [1]. The AOS consists in deterministic reversal processes of magnetic domains induced by femtosecond laser pulses. This phenomenon allows for ultrafast and photon-helicity dependent magnetization switching [2-5] (Fig. 1a) to occur in magnetic thin films and multilayers. AOS occurs in magnetic metamaterials consisting on a wide variety of magnetic thin film materials, including rare- earth alloy thin films and/or transition metal-ferromagnetic material multilayers. In the latter case, a full magnetic characterization of the magnetic behaviour of the multilayer system (FIG. 1b) is crucial to reveal the true mechanism of AOS, as allowing us to tune the material parameters to improve the AOS induction mechanism and phenomena. In this work we show a polarized neutron reflectometry study (FIG. 1c-d) of Co/Pt ferromagnetic multilayer thin films where AOS has been observed, with the objective to relate the quality of the interfaces, possible interlayer diffusion events and the magnetic spin-depth profile onto the observed AOS mechanism and the magnetic properties of the multilayers. [1] A. Kimel. and M. Li, Nat. Rev. 4, 189, (2019) [2] C. D. Stanciu et al.,Phys. Rev. Lett. 99, 047601, (2007) [3] Y. Quessab et al. Phys. Rev. B. 97 (2018) [4] Y. Liu et al. Appl. Phys. Lett., 122 (2023) [5] G. Kichin et al. Phys. Rev. Appl., 12 (2019)

The Application of Polarized Neutron Imaging in Materials Sciences

• Nikolay Kardjilov

Hydrated protein dynamics using polarised neutrons

• Agathe Nidriche

Polarized neutron reflectometry for investigation of low-dimensional 2D magnetic & superconducting periodic and quasiperiodic heterostructures (Download the latest program here)

• Vladimir Zhaketov (Joint Institute for Nuclear Research)

Low-dimensional magnetic and superconducting heterostructures, due to the presence of a large number of interesting phenomena, are currently being actively studied. One of the effective methods for studying magnetism is polarized neutron reflectometry, which makes it possible to obtain isotopic and magnetic depth profiles with nanometer resolution. Low-temperature studies of proximity effects in superconducting-ferromagnetic systems [1] and rare-earth films with nontrivial magnetic ordering [2] were carried out using the REMUR reflectometer of the IBR-2 reactor (Dubna). Proximity effects at the interface between two media are currently being actively studied. Of particular interest are layered low-dimensional structures with superconducting (S) and ferromagnetic (F) properties, in which the interaction of two antagonistic order parameters is realized. Promising systems for studying proximity effects are S/F heterostructures made of niobium and rare earth (RE) metals [3]. As example for the layered heterostructure Al2O3//Nb(40 nm)/[Dy(6 nm)/Ho(6 nm)]34/Nb(10 nm) it was found that at a temperature below the superconducting transition, the magnetic state of the helimagnet was affected by superconductivity, namely the fan-shaped magnetic state the ordering was rearranged into helimagnetic ordering [4]. The described periodic layered systems are artificial layered crystals. When neutrons are reflected from a periodic layered structure, Bragg peaks are observed. Layered artificial quasicrystals are also of particular interest. It is possible to create artificial layered systems with quasicrystallinity in the direction perpendicular to the plane of the structure. The possibility of creating layered quasicrystals from alternating superconducting and ferromagnetic layers is considered. These model systems are simple to manufacture and research, but will make it possible to study non-trivial phenomena, such as fractal superconductivity and long-range magnetic order in a quasiperiodic system, as well as their coexistence. The creation of Fibonacci structures using magnets with helical magnetic order is of particular interest. [1] Yu.V. Nikitenko et al. // Physics of Particles and Nuclei, v. 53, No. 6, pp. 1089-1125 (2022). [2] D.I. Devyaterikov et al. // Journal of Surface Investigation, v. 16, № 5, pp. 839-842 (2022). [3] Khaydukov Yu.N. et al. // Phys. Rev. B, vol. 99, pp. 140503(R) (2019). [4] Zhaketov V.D. et al. // Physics of the Solid State, Vol. 65, No. 7 (2023).

Field induced structures in colloidal solution of hexaferrite nanoparticles (Download the latest program here)

• Natalia Grigoryeva (M.N. Mikheev Institute of Metal Physics, UB RAS)
• Sergey Grigoriev (NRC "Kurchatov Institute" - Petersburg Nuclear Physics Institute)

Plate-like strontium hexaferrite particles SrFe$_{12}$O$_{19}$ have an average size of 50 nm$\times$ 5 nm and coercive force of about 5000 Oe. When dissolved in water, these particles disperse in space with random orientations, but cause of anisotropic steric interactions readily turn and align in magnetic fields demonstrating a phase transition of isotropic-nematic liquid. We use the small angle polarized neutron scattering (P-SANS) technique to study the effect of a magnetic field on the structural ordering of the ferrofluid. The P-SANS experiments were performed at the VSANS facility of the Chinese Spallation Neutron Source (CSNS). The beam of neutrons polarized up to $P_0=0.95$ within a wavelength range from 0.22 to 0.67 nm was used. SANS patterns were taken for the sample having no magnetic prehistory and then exposed to the external magnetic field from 0.0005 to 0.9 T. The two dimensional maps of the SANS intensity reveal a diffuse isotropic scattering at small fields $H < H_c = 0.001$ T and a series of diffraction reflections appeared along the field axis ($H \gg H_c$) at $q_b, 2q_b, 3q_b$, where $q_b = 0.3$ nm$^{–1}$, which corresponds to the particle ordering at a distance of 21 nm, approximately. The nuclear-magnetic interference scattering obtained from the difference of intensities with a neutron spins parallel and antiparallel to magnetic field reveals two additional peaks in the direction perpendicular to the field at $q_{\perp} = 0.06$ nm$^{–1}$. It implies appearance of nematic ordering with the period of 100 nm. Thus, we conclude that upon magnetization process three structural states of the ferrofluid can be identified in different magnetic field regions. Long-range but disordered magnetic chains of hexaferrite particles are formed in a nonmagnetized sample at low fields $ H < H_{c}$. These chains are transformed into structurally curved (spiral-like) structures oriented along the magnetic field at $H > H_{c}$. These spirals are broken into short strait columns of the 10-12 particles directed rigidly along the magnetic field at $H >> H_{c}$. The columns are organized in the nematic structure and its period decreases with increase of magnetic field. These findings are supported by the numerical simulations of the colloidal solution in magnetic field.

Spin-polarized neutron scattering study of unusual magnetic states in candidate Kitaev magnet Na3Co2SbO6

• Yuan Li

Magnon polarons and chiral phonons in multiferroic Fe2-xZnxMo3O8 systems

• Song Bao

Diffuse small-angle neutron scattering signatures of the Dzyaloshinkii-Moriya interaction (Download the latest program here)

• Andreas Michels (University of Luxembourg)

The antisymmetric Dzyaloshinkii-Moriya interaction (DMI) arises in systems with broken inversion symmetry and strong spin-orbit coupling. In conjunction with the isotropic and symmetric exchange interaction, magnetic anisotropy, the dipolar interaction, and an externally applied magnetic field, the DMI supports and stabilizes the formation of various kinds of complex mesoscale magnetization configurations, such as helices, spin spirals, skyrmions, or hopfions. A question of importance in this context addresses the neutron scattering signature of the DMI, in particular in polycrystalline bulk materials and random nanoparticle assemblies, where the related magnetic neutron scattering signal is diffuse in character and not of the single-crystal diffraction-peak type, as it is e.g. seen for a skyrmion lattice in the B20 compounds. In this talk we discuss (i) the effect of the DMI in spherical FeGe nanoparticles on the randomly averaged magnetic neutron scattering observables, more specifically on the spin-flip small-angle neutron scattering cross section, the related chiral function, and the pair-distance distribution function. Additionally, (ii) recent theoretical results regarding the diffuse scattering signatures of two types of stable hopfions in the SANS observables are presented, and (iii) experimental data for the less well studied microstructural defect-induced DMI are discussed.

Spin waves in full-polarized state of Dzyaloshinskii-Moriya helimagnets: polarized SANS study (Download the latest program here)

• Sergey Grigoryev (NRC "Kurchatov Institute" - Petersburg Nuclear Physics Institute)

The cubic noncentrosymmetric structure of the B20 compounds causes the formation of a spin spiral with a wave vector $k_s = D/J$ balanced by the competition of antisymmetric Dzyaloshinskii-Moriya (DM) interaction and the ferromagnetic exchange interaction (Back-Jensen model) [1,2]. The application of a magnetic field $H$ transforms the helix into a conical structure, which collapses into a field-induced ferromagnet at point $H_{C2}$. This field is defined by the interaction hierarchy through $gμ_BH_{C2} = Ak_s^2$, where $A = J/S$ is the spin-wave stiffness. This ratio between $H_{C2}$, $A$ and $k_S$ was experimentally tested for a large number of B20 compounds: MnSi [3], Mn$_{1−x}$Fe$_x$Si [4], FeGe [5], Mn$_{1−x}$Fe$_x$Ge [6], Fe$_{1−x}$Co$_x$Si [7,8],Cu$_2$OSeO$_3$ [9]. The above ratio was proven to be valid for all the above mentioned compounds within the whole temperature range from 0 to $T_C$. To order to perform these experimental tests, we develop a technique to study the spin wave dynamics of the full-polarized state of the Dzyaloshinskii-Moriya helimagnets by polarized small-angle neutron scattering. We have experimentally proven that the spin waves dispersion in this state has the anisotropic form given by M.Kataoka in [10]: $\epsilon_q = A({\bf q} – {\bf k}_s)^2 + g\mu_B(H –H_{C2})$. We show that the neutron scattering image displays a circle with a certain radius, which is centered at the momentum transfer corresponding to the helix wave vector in helimagnetic phase ${\bf k}_s$, which is oriented along the applied magnetic field $H$. The radius of this circle is directly related to the spin-wave stiffness $A$ of this system. This scattering depends on the neutron polarization showing the one-handed nature of the spin waves in Dzyaloshinskii-Moriya helimagnets in the full-polarized phase. Thus the spin wave stiffness $A$ can be measured in the fast mode in the wide temperature range and for a large variety of samples. We have found that the spin-wave stiffness A change weakly with temperature for each individual compound but remarkable is a change of $A$ with the concentration $x$ for the Mn$_{1−x}$Fe$_x$Si compounds [4] and for the Fe$_{1−x}$Co$_x$Si compounds [8]. A detailed picture of these changes and their interpretations will be reported. References: [1] P. Bak, M.H. Jensen, J. Phys. C13 (1980) L881. [2] O. Nakanishi, A. Yanase, A. Hasegawa, M. Kataoka, Solid State Commun. 35 (1980) 995. [3] S. V. Grigoriev, A. S. Sukhanov, E. V. Altynbaev, S.-A. Siegfried, A. Heinemann, P. Kizhe, and S. V. Maleyev, Phys. Rev. B 92, 220415(R) (2015). [4] S. V. Grigoriev, E. V. Altynbaev, S.-A. Siegfried, K. A. Pschenichnyi, D. Menzel, A. Heinemann, and G. Chaboussant, Phys. Rev. B 97, 024409 (2018). [5] S.-A. Siegfried, A. S. Sukhanov, E. V. Altynbaev, D. Honecker, A. Heinemann, A. V. Tsvyashchenko, and S. V. Grigoriev, Phys. Rev. B 95, 134415 (2017). [6] S. V. Grigoriev, E. V. Altynbaev, S.-A.Siegfried, K. A. Pshenichnyi, D. Honnecker, A. Heinemann, A. V. Tsvyashchenko, JMMM 459, 159-164 (2018). [7] S. V. Grigoriev, K. A. Pshenichnyi, E. V. Altynbaev, S.-A. Siegfried, A. Heinemann, D. Honnecker, and D. Menzel, JETP Letters, 107, No. 10, pp. 640–645 (2018). [8] S. V. Grigoriev, K. A. Pschenichnyi, E. V. Altynbaev, S.-A. Siegfried, A. Heinemann, D. Honnecker, and D. Menzel, Phys. Rev. B 100 N. 9 pp. 094409 (2019) [9] S. V. Grigoriev, K. A. Pschenichnyi, E. V. Altynbaev, A. Heinemann, and A. Magrez, Phys. Rev. B 99, 054427(2019) [10] M. Kataoka, J.Phys.Soc.Jap. 56, 3635 (1987).

KWS-3 Very Small Angle Neutron Scattering Diffractometer: Current Status with a Focus on Polarization and Analysis Options (Download the latest program here)

• Vitaliy Pipich (Jülich Centre for Neutron Science JCNS at Heinz Maier-Leibnitz Zentrum MLZ, Forschungszentrum Jülich GmbH, Garching, Germany)

KWS-3 "VerySANS" is a very-small-angle-neutron-scattering diffractometer operated by Jülich Centre for Neutron Science JCNS at Heinz Maier-Leibnitz Zentrum MLZ in Garching, Germany. The principle of this instrument is one-to-one imaging of an entrance aperture onto a 2D position sensitive detector by neutron reflection from a double-focusing toroidal mirror to achieve a high Q-resolution $3·10^{-5}$ Å. In “standard mode” with Q-range between $10^{-4}$ and $2.5·10^{-3}$ Å KWS-3 demonstrates worldwide best performance: intensity much higher than any pinhole SANS instrument and measurement time much shorter than any Bonse-Hart camera. Recently, we have finalized a multi-sample-position instrument concept: we have been able to propose optimal configurations with high flux and low background covering three decades within Q-range $3·10^{-5}$ and $3·10^{-2}$ Å. We can also offer a "SANS" configuration for strongly scattering samples with sample-to-detector distance between 5 and 40 cm covering the Q-range of a classical SANS instrument between $2.5·10^{-3}$ and 0.35 Å. Tilt stages/rotation table for the sample environment (SE) up to 500 kg have been commissioned as a mobile device and could be used across the whole instrument Q-range. Polarized neutrons and a supermirror analyzer represent a novel option now available.

Wide-range wavelength-tunable laser for studies of 3He neutron spin filter cells (Download the latest program here)

• Takashi Ino (KEK)

See attached PDF file.

Development and performance evaluation of 3He neutron spin filters at J-PARC (Download the latest program here)

• Ryuju Kobayashi (JAEA)

The $^3$He neutron spin filter ($^3$He NSF) is a neutron polarization device that uses polarized $^3$He nuclei. It can polarize a wide range of neutron energies, including the epithermal neutron, making it a suitable polarization device for spallation neutron sources. The polarization of $^3$He nuclei is achieved through the Spin-Exchange Optical Pumping (SEOP) method. The SEOP method, using a high-intensity laser, slight heating (200 ℃), and a small magnetic field (2 mT), enables the achievement of a very high $^3$He polarization with compact setup. Our group is developing and operating a $^3$He NSF at J-PARC. Since the first user experiment in 2017[1], we have conducted more than 80 days of operational use per year. Recently, we developed compact in-situ SEOP systems for the ³He NSF, specifically designed to fit within the limited installation space at J-PARC’s neutron beamlines. This advancement is expected to increase experimental applications. On the other hand, there is an unanswered puzzle about the $^3$He NSF. It concerns the relaxation mechanism of $^3$He nuclei. The complex behavior of $^3$He atoms contained in glass cells creates a barrier to the fabrication of high-performance $^3$He cell for the $^3$He NSF. We are investigating the relationship between the fabrication method and performance of the $^3$He cell, aiming to contribute to the understanding of the relaxation mechanism. We have developed an evaluation system for the $^3$He cell. This system features the ability to directly and precisely measure magnetic fields, which are an environmental factor included in conventional evaluation methods using NMR. This capability allows for quantitative evaluation independent of the $^3$He cell's shape. Using this method, we evaluated multiple $^3$He cells and obtained consistent results. In this presentation, we will describe an overview of the $^3$He NSF development at J-PARC and discuss the results of the performance evaluation of the $^3$He cells.

Separation of coherent and incoherent scattering from 1H-containing samples using polarized neutrons with ex-situ 3He spin filters (Download the latest program here)

• Shusuke Takada (Tohoku University)

Polarized neutron beams, generated using $^3$He spin filters, provide a valuable approach for separating coherent and incoherent scattering, nuclear and magnetic scattering, and for observing symmetry violations in nuclear reactions. The $^3$He spin filter is suitable for polarizing neutrons with energies ranging from meV to eV, making effective use of J-PARC's high-intensity pulsed neutron beams that cover a wide energy range. The number of user experiments with a $^3$He spin filter in J-PARC has increased annually [1], reaching about 10 experiments per year in recent years. This presentation focuses on the application of the $^3$He spin filter for measurements of coherent scattering from hydrogen-containing samples. Hydrogen is a fundamental constituent of biomolecules, yet the underlying mechanisms of hydrogen bond formation remain an open question. However, incoherent scattering from hydrogen often affects significantly to background noise, complicating accurate structural analyses of samples in neutron experiments. The experiment was conducted at the BL21 NOVA beamline at J-PARC, which can perform measurements in the high-Q region with high-intensity neutron beams, facilitating precise pair distribution function (PDF) analyses. Integrating NOVA with $^3$He spin filters allows for separation of coherent and incoherent scattering components and high-precision PDF analysis. As part of our efforts to establish a method for separating the components of coherent and incoherent scattering by neutron spin analysis using the $^3$He spin filters, we have started to analyze the data in combination with Monte Carlo simulations. Incoherent scattering of neutrons in a sample is known to flip the neutron spin direction with a probability of 2/3. However, in cases of multiple scattering, the probability of spin flips may vary, which reduces the accuracy of the separation between coherent and incoherent scattering components. We have used Geant4, which is a toolkit for the simulation of the passage of particles through matter, to estimate the spin-flip probability due to multiple scattering. This presentation will report on the details of the polarized neutron spin analysis experiments carried out with the $^3$He spin filter in NOVA and the current status of the data analysis.

The Status of Sample Environment at CSNS

• 海韬 胡 (高能所)

Probing Zigzag Magnetism in α-RuCl3 via Spherical Neutron Polarimetry

• Xiao Wang (China Spallation Neutron Source Science Center)

Honeycomb-lattice materials such as α-RuCl₃ have drawn significant attention for their bond-directional, Kitaev-like exchange interactions, which can stabilize unconventional magnetic ground states [1]. Despite these strong Kitaev couplings, α-RuCl₃ displays a long-range zigzag antiferromagnetic order at low temperatures. A persistent challenge in characterizing this order is the small ordered moment of Ru³⁺, which complicates precise determination of the magnetic structure. In particular, whether the moments are strictly collinear or exhibit a small in-plane tilt remains an open question. Here, we demonstrate how spherical neutron polarimetry (SPN) can overcome this challenge. By performing SPN measurements on a cold-neutron three-axis spectrometer equipped with a zero-field polarimeter, we collected the full polarization matrices at magnetic Bragg positions (±0.5, 0, ℓ). This method allows a direct, model-independent separation of nuclear and magnetic scattering signals, providing high sensitivity to the ordered moment direction in spite of its small magnitude. Through comparative analysis of the data, we show that a slightly tilted moment arrangement — with a small (~10°) in-plane component — can account for all elements of the measured polarization matrices more convincingly than a strictly collinear zigzag. These results highlight the subtle nature of the magnetic order in α-RuCl₃ and underscore the efficacy of spherical neutron polarimetry for resolving small moment canting in quantum magnets. [1] G. Jackeli and G. Khaliullin, Phys. Rev. Lett. 102, 017205 (2009).

Towards the development of polarization analysis with high energy resolution for SPHERES (Download the latest program here)

• Chuyi Huang (Jülich Centre for Neutron Science)

Neutron polarization analysis provides profound additions of knowledge to the field of soft condensed matter research. The ability to separate the coherent and incoherent scattering contributions gives information on spatial correlations and collective motion, and information from single particles, respectively. In this study, we focus on upgrading the SPHERES (SPectrometer for High Energy RESolution) backscattering instrument at JCNS [1,2] to meet the demands for high energy resolution and polarization analysis. Because of geometry constraints the polarization analyzer would need to be located between the sample and the Si111 analyzers. Based on this design, we explore transmission wide angle polarizer supermirror analyzer option through Monte-Carlo simulations [3]. At this conference, we will present our work towards performing polarization analysis with the high-resolution capabilities at the SPHERES instrument. [1] J.Wuttke, Rev. Sci. Instrum. 83, 075109 (2012) [2] J.Wuttke, Rev. Sci. Instrum. 84, 115108 (2013) [3] P. Böni, Nucl. Instrum. Methods Phys. Res. Sect. A 966, 163858 (2020)

Trimer formation in the purely organic multiferroic magnet TNN·CH$_3$CN (Download the latest program here)

• Javier Campo (Aragón Nanoscience and Materials Institute (CSIC-University of Zaragoza))

Equilateral spin triangles have long been a topic of interest in quantum magnetism, offering a fertile ground to explore phenomena such as frustration [1], spin-electric coupling [2], and multiferroic ordering [3]. Despite substantial progress, realizing ideal triangular spin networks remains a challenge, often hindered by structural distortions. The organic compound TNN·CH₃CN overcomes these limitations with its isotropic organic radical spins, free from Jahn-Teller effects, allowing uniform exchange interactions. This makes TNN·CH₃CN an ideal candidate for investigating the novel multiferroic phases predicted by Kamiya and Batista [3]. In this work, we focus on the 1/3 magnetization plateau (1.25 < B < 8.49 T), where TNN·CH₃CN exhibits a twofold-degenerate S=1/2, Sz=1/2 ground state [4]. This intriguing phase exhibits ferroelectric order below 0.35 K without a conventional spin-ordering transition, offering a unique window into the interplay between spin and electric properties in triangular spin systems. By employing polarized neutron diffraction (PND) and muon spin relaxation (μSR) techniques, we investigate the emergence of collective spin behavior within the plateau [5]. The results align well with theoretical predictions and highlight the trimer formation at low temperatures, where the initially independent paramagnetic spins couple below 5.5 K. [1] J. F. Nossa and C. M. Canali, Phys. Rev. B, 89, 235435 (2014). [2] S. Nakatsuji et al., Science, 309, 1697-1700 (2005). [3] Y. Kamiya and C. D. Batista, Phys. Rev. Lett., 108, 097202 (2012). [4] C. P. Aoyama, PhD thesis, University of Florida (2015). [5] M. Pardo-Sainz, PhD thesis, University of Zaragoza (2024).

Nuclear and magnetic structure of ferrofluids for power transformers by SANS

• Petrenko Viktor

Advances in design simulation of supermirror polariser (Download the latest program here)

• Wai Tung Lee (European Spallation Source ERIC)

Neutron polariser and analyser based on polarising supermirror technology [1-3] have been enabling the widespread use of polarised neutrons in the past decades. Polarising supermirror operates on polarised neu- tron reflectometr yprinciple san di shighl ysensitiv et oinciden tneutro’s wavelength and incident angle. Modern neutron beamline ofte nuse sneutro noptica lelement ssuc ha s acombinatio no fcurve dan delliptica neutron guides to get out of the line of sight to the moderator, increase the transport of selected neutrons and focus the beam onto a sample. A polariser is placed either inline in a section of the neutron guides or at the guide exit in the experimental enclosure. At those locations, the beam characteristics are complex, making it necessary to use simulation for the design evaluation of the polariser. At present, the leading sim- ulation softwar ear eMcSta s[4,5 ]an dVites s[6] .Whil eman ypolarisin gdevice shav ebee nincorporated ,th complexity of the interaction between neutron and polarising supermirror and the increasing sophistication of beamline design demand further development of the simulation code to include physical processes that could previously be omitte d[7] .W erepor ther e adevelopmen tthat ,i nadditio nt opolarisation-dependen reflectio nan dtransmissio na tth esupermirro rcoating ,als oinclude stransmissio nan dabsorptio ni nsubstrate refraction at the substrate interface, and multiple internal reflectio ni ndouble-sid ecoate dsupermirror .A tth device level, multiple reflectio nbetwee nsupermirror sha sals obee ninclude din ,e.g .v-cavit ypolariser .T results revealed internal reflection si n asubstrat ean dcross-tal kbetwee nsupermirror sca nsignificant lyaff the performance. Consequently, mitigations have been incorporated in our polariser designs to archive, for instance, 95% polarisation and 42% transmission at 2 Å for a v-cavity polariser. We will present our finding and the results of polariser design for ESS instruments using the new code. [1] P. Böni, Physica B 234-236, 1038 (1997). [2] T. Krist, C. Lartigue, F. Mezei, Physica B 180-181, 1005 (1992). [3] T. Bigault, et. al., J. Phys.: Conf. Ser. 528, 012017 (2014). [4] P. Willendrup and K. Lefmann, J. Neutron Res. 22, 1 (2020). [5] P. Willendrup and K. Lefmann, J. Neutron Res. 23, 7 (2021). [6] K. Lieutenant, et. al., Proc. SPIE Int. Soc. Opt. Eng. 5536, 134 (2004). [7] D. M. Rodríguez, et. al., EPJ Web of Conferences 286, 03008 (2023). E-mail of the corresponding author: waitung.lee@ess.eu

Development of Polarized 3He at CSNS

• Junpei 张俊佩 (高能所)

Progress in MEOP based 3He Polarization System

• Lianyong Wu

Polarized neutron Imaging development at the CSNS

• Tianhao Wang (中科院高能物理研究所)

Polarized Neutron Observation and Modeling of Pinned Magnetic Fields in Superconductors

• Siqin Meng

Recent progress of polarized neutron imaging technique at China Advanced Research Reactor

• 正耀 李 (中国原子能科学研究院)

Closing：Excellent Poster Award