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Magnetic materials are composed of the simple building blocks of magnetic moments on a crystal lattice that interact via magnetic exchange. Yet from this simplicity emerges a remarkable diversity of magnetic states. Some reveal the deep quantum mechanical origins of magnetism, for example, quantum spin liquid (QSL) states in which magnetic moments remain disordered at low temperatures despite being strongly correlated through quantum entanglement. A promising theoretical model of a QSL is the Kitaev model, composed of unusual bond-dependent exchange interactions, but experimentally, this model is challenging to realise. Here we show that the material requirements for the Kitaev QSL survive an extended pseudo-edge-sharing superexchange pathway of Ru 3+ octahedra within the honeycomb layers of the inorganic framework solid, RuP 3 SiO 11 . We confirm the requisite j eff = 1 2 state of Ru 3+ in RuP 3 SiO 11 and resolve the hierarchy of exchange interactions that provide experimental access to an unexplored region of the Kitaev model., Competing Interests: Competing interests The authors declare no competing interests., (© 2024. The Author(s).)

The magnetic properties of a 2D layered material consisting of high-spin Co 2+ complexes, [Co(NH 3 NH 2 ) 2 (H 2 O) 2 Cl 2 ]Cl 2 ( CoHyd 2 Cl 4 ), have been extensively characterized using electron paramagnetic resonance, magnetic susceptibility, and low-temperature heat capacity measurements. Electron paramagnetic resonance spectroscopy studies suggest that below 50 K, the J = 3/2 orbital triplet state of Co is gradually depopulated in favor of the J = 1/2 spin state, which is dominant below 20 K. In light of this, the magnetic susceptibility has been fitted with a two-level model, indicating that the interactions in this material are much weaker than previously thought. This two-level model is unable to fit the data at low temperatures and, combined with electron paramagnetic resonance spectroscopy, suggests that ferromagnetic interactions between Co 2+ cations in the J = 1/2 state become significant approaching 2 K. Heat capacity measurements suggest the emergence of a long-range ordered state below 246 mK, which neutron diffraction confirms to be ferromagnetic., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Spin-orbit coupling offers a large variety of novel and extraordinary magnetic and electronic properties in otherwise 'ordinary pool' of heavy ion oxides. Here we present a detailed study on an apparently isolated hexagonal 2 H spin-chain d 4 iridate Sr 3 LiIrO 6 with geometric frustration. Our structural studies reveal Li-Ir chemical order with desired stoichiometry in this compound, while x-ray absorption together with x-ray photoemission spectroscopic characterizations establish pure 5+ valence of Ir. We have established a magnetic ground state with finite Ir 5+ magnetic moments in this compound, contrary to the anticipated nonmagneticJeff= 0 state, through combined dc susceptibility,7Li nuclear magnetic resonance (NMR), muon spin relaxation ( µ SR) and ab-initio electronic structure studies. These investigations together with ac magnetic susceptibility and specific heat measurements reveal that despite having noticeable antiferromagnetic correlation among the Ir 5+ local moments, this system does not magnetically order down to at least 0.05 K, possibly due to geometrical exchange frustration, arising from the comparable nearest- and next-nearest-neighbor interchain Ir-O-O-Ir superexchange interaction strengths with opposite signs. However, the zero-field µ SR analysis shows emergence of a considerable proportion of spin-freezing on top of a spin-fluctuating dynamic magnetic background down to the lowest measured temperature of 1.7 K, possibly due to some inhomogeneity and/or the much stronger intra-column Ir-Ir magnetic exchange interaction strength relative to the inter-column Ir-Ir ones. The linear temperature dependence of the magnetic specific heat (Cm) in both zero and applied magnetic fields, plus the power-law behavior of the NMR spin-lattice relaxation rate suggest a gapless spinon density of states in this charge gapped disordered magnetic ground state of Sr 3 LiIrO 6 ., (Creative Commons Attribution license.)

We present a comprehensive study of PrIr 3 B 2 , which includes a detailed investigation of its crystal and magnetic structure using neutron diffraction. AC and DC magnetization and heat capacity data reveal antiferromagnetic ordering at T N = 10 K. The heat capacity measurements further exhibit a broad peak near 270 K which is related to a structural transition from P 6/ mmm to C 2/ m seen in low temperature x-ray diffraction and neutron diffraction. High intensity neutron diffraction data confirm the long-range ordering of Pr 3+ spins, with no apparent magnetic moment on either of the Iridium sites. Two possible magnetic structures with either k 1 = [1,0,0] or k 2 = [½,½,0] fit nearly equally well the neutron diffraction data. However, based on previous magnetization studies on a single crystalline sample it is argued that the second solution with k 2 corresponds to the appropriate magnetic structure of PrIr 3 B 2 below 10 K. In this magnetic structure, the Pr 3+ moments are oriented at ∼45° to both the a and b axes, with the c -axis being the hard axis of magnetization. Overall, our results provide new insights into the magnetic and structural properties of PrIr 3 B 2 ., (© 2023 IOP Publishing Ltd.)

A promising route to discover exotic electronic states in correlated electron systems is to vary the hole or electron doping away from a Mott insulating state. Important examples include quantum criticality and high-temperature superconductivity in cuprates. Here, we report the surprising discovery of a quantum insulating state upon electron doping the Mott insulator CeMnAsO, which emerges below a distinct critical transition temperature, T II . The insulator-insulator transition is accompanied by a significant reduction in electron mobility as well as a colossal Seebeck effect and slow dynamics due to decoupling of the electrons from the lattice phonons. The origin of the transition is tentatively interpreted in terms of many-body localization, which has not been observed previously in a solid-state material., (© 2023. The Author(s).)

This work investigates the acid sites in a commercial ZSM-5 zeolite catalyst by a combination of spectroscopic and physical methods. The Brønsted acid sites in such catalysts are associated with the aluminum substituted into the zeolite lattice, which may not be identical to the total aluminum content of the zeolite. Inelastic neutron scattering spectroscopy (INS) directly quantifies the concentrations of Brønsted acid protons, silanol groups, and hydroxyl groups associated with extra-framework aluminum species. The INS measurements show that ∼50% of the total aluminum content of this particular zeolite is extra framework, a conclusion supported by solid-state NMR and ammonia temperature-programmed desorption (TPD) measurements. Evidence for the presence of extra-framework aluminum oxide species is also seen in neutron powder diffraction data from proton- and deuterium-exchanged samples. The differences between results from the different analytical methods are discussed, and the novelty of direct proton counting by INS in this typical commercial catalyst is emphasized., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

The magneto-optical and dielectric behavior of M-type hexaferrites as permanent magnets in the THz band is essential for potential applications like microwave absorbers and antennas, while are rarely reported in recent years. In this work, single-phase SrFe 12- x Nb x O 19 hexaferrite ceramics were prepared by the conventional solid-state sintering method. Temperature dependence of dielectric parameters was investigated here to determine the relationship between dielectric response and magnetic phase transition. The saturated magnetization increases by nearly 12%, while the coercive field decreases by 30% in the x = 0.03 composition compared to that of the x = 0.00 sample. Besides, the Nb substitution improves the magneto-optical behavior in the THz band by comparing the Faraday rotation parameter from 0.75 ( x = 0.00) to 1.30 ( x = 0.03). The changes in the magnetic properties are explained by a composition-driven increase of the net magnetic moment and enhanced ferromagnetic exchange coupling. The substitution of the donor dopant Nb on the Fe site is a feasible way to obtain multifunctional M-type hexaferrites as preferred candidates for permanent magnets, sensors, and other electronic devices.

Layered Sr 2 M 3 As 2 O 2 -type oxypnictides are composed of tetrahedral M 2 Pn 2 and square planar MO 2 layers, the building blocks of iron-based and cuprate superconductors. To further expand our understanding of the chemical and magnetic properties of the Sr 2 Cr 3- x Mn x As 2 O 2 solid solution, Sr 2 Cr 2 MnAs 2 O 2 has been synthesized. The compound crystallizes in the I 4/ mmm tetragonal space group with a refined stoichiometry of Sr 2 Cr 1.85 Mn 1.15 As 2 O 2 . The M(2) site within the M 2 Pn 2 slab is occupied by 42.7% Cr and 57.3% Mn, and the magnetic moments order antiferromagnetically below T N (M2) = 540 K with a C-type antiferromagnetic structure. The M(1) site within the MO 2 layers is fully occupied by Cr, and antiferromagnetic order is observed below T N (M1) = 200 K. Along c , there are two possible interplanar arrangements: ferromagnetic with the (1/2, 1/2, 0) propagation vector and antiferromagnetic with the (1/2, 1/2, 1/2) propagation vector. Magnetic phase separation arises so that both propagation vectors are observed below 200 K. Such magnetic phase separation has not been previously observed in Sr 2 M 3 As 2 O 2 phases (M = Cr, Mn) and shows that there are several competing magnetic structures present in these compounds.

Extended solid-state materials based on the hexagonal perovskite framework are typified by close competition between localized magnetic interactions and quasi-molecular electronic states. Here, we report the structural and magnetic properties of the new six-layer hexagonal perovskite Ba 3 CaMo 2 O 9 . Neutron diffraction experiments, combined with magnetic susceptibility measurements, show that the Mo 2 O 9 dimers retain localized character down to 5 K and adopt nonmagnetic spin-singlet ground states. This is in contrast to the recently reported Ba 3 SrMo 2 O 9 analogue, in which the Mo 2 O 9 dimers spontaneously separate into a mixture of localized and quasi-molecular ground states. Structural distortions in both Ba 3 CaMo 2 O 9 and Ba 3 SrMo 2 O 9 have been studied with the aid of distortion mode analyses to elucidate the coupling between the crystal lattice and electronic interactions in 6H Mo 5+ hexagonal perovskites.

When polymer composites containing magnetic nanoparticles (MNPs) are exposed to an alternating magnetic field, heat is generated to melt the surrounding polymer locally, partially filling voids across any cracks or deformities. Such materials are of interest for structural applications; however, structural polymers with high melting temperatures pose the challenge of generating high localised temperatures enabling self-healing. A method to prepare a multiferroic-Polyamide 6 (PA6) nanocomposite with tuneable magnetocaloric properties is reported. Tunability arises from varying the MNP material (and any coating, its dispersion, and agglomerate sizes in the nanocomposite). The superparamagnetic MNPs (SMNPs) and iron oxide MNPs with and without surface functionalization were dispersed into PA6 through in situ polymerization, and their magnetic properties were compared. Furthermore, computer simulations were used to quantify the dispersion state of MNPs and assess the influence of the interaction radius on the magnetic response of the self-healable magnetic nanoparticle polymer (SHMNP) composite. It was shown that maintaining the low interaction radius through the dispersion of the low coercivity MNPs could allow tuning of the bulk magnetocaloric properties of the resulting mesostructures. An in-situ polymerization method improved the dispersion and reduced the maximum interaction radius value from ca. 806 to 371 nm and increased the magnetic response for the silica-coated SMNP composite. This sample displayed ca. three orders of magnitude enhancement for magnetic saturation compared to the unfunctionalized Fe 3 O 4 MNP composite., (© 2022. The Author(s).)

This work describes a homometallic spin- 1 / 2 tetrabromocuprate adopting a bilayer structure. Magnetic-susceptibility measurements show a broad maximum centred near 70 K, with fits to this data using a Heisenberg model consistent with strong antiferromagnetic coupling between neighbouring copper atoms in different layers of the bilayer. There are further weak intralayer ferromagnetic interactions between copper cations in neighbouring dimers. First-principles calculations are consistent with this, but suggest there is only significant magnetic coupling within one direction of a layer; this would suggest the presence of a spin ladder within the bilayer with antiferromagnetic rung and weaker ferromagnetic rail couplings., (© 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Isovalent nonmagnetic d 10 and d 0 B″ cations have proven to be a powerful tool for tuning the magnetic interactions between magnetic B' cations in A 2 B'B″O 6 double perovskites. Tuning is facilitated by the changes in orbital hybridization that favor different superexchange pathways. This can produce alternative magnetic structures when B″ is d 10 or d 0 . Furthermore, the competition generated by introducing mixtures of d 10 and d 0 cations can drive the material into the realms of exotic quantum magnetism. Here, Te 6+ d 10 was substituted by W 6+ d 0 in the hexagonal perovskite Ba 2 CuTeO 6 , which possesses a spin ladder geometry of Cu 2+ cations, creating a Ba 2 CuTe 1- x W x O 6 solid solution ( x = 0-0.3). We find W 6+ is almost exclusively substituted for Te 6+ on the corner-sharing site within the spin ladder, in preference to the face-sharing site between ladders. The site-selective doping directly tunes the intraladder, J rung and J leg , interactions. Modeling the magnetic susceptibility data shows the d 0 orbitals modify the relative intraladder interaction strength ( J rung / J leg ) so the system changes from a spin ladder to isolated spin chains as W 6+ increases. This further demonstrates the utility of d 10 and d 0 dopants as a tool for tuning magnetic interactions in a wide range of perovskites and perovskite-derived structures.

In this study, we investigate the effect of thermal treatment/calcination on the stability and activity of a Na-Mn-W/SiO 2 catalyst for the oxidative coupling of methane. The catalyst performance and characterisation measurements suggest that the W species are directly involved in the catalyst active site responsible for CH 4 conversion. Under operating conditions, the active components, present in the form of a Na-W-O-Mn molten state, are highly mobile and volatile. By varying the parameters of the calcination protocol, it was shown that these molten components can be partially stabilised, resulting in a catalyst with lower activity (due to loss of surface area) but higher stability even for long duration OCM reaction experiments.

Detailed elemental analysis and low-temperature calorimetric measurement results are reported for the first time for Gram-positive bacteria, Gram-negative bacteria and mold fungi. Microorganism unit carbon formulas (empirical formulas) were calculated. Standard molar heat capacity and entropy were found to be C⁰ p,m = 38.200 J/C-mol K and S⁰ m = 31.234 J/C-mol K for Escherichia coli, C⁰ p,m = 54.188 J/C-mol K and S⁰ m = 47.141 J/C-mol K for Gluconobacter oxydans, C⁰ p,m = 31.475 J/C-mol K and S⁰ m = 33.222 J/C-mol K for Pseudomonas fluorescens, C⁰ p,m = 38.118 J/C-mol K and S⁰ m = 37.042 J/C-mol K for Streptococcus thermophilus, and C⁰ p,m = 35.470 J/C-mol K and S⁰ m = 34.393 J/C-mol K for Penicillium chrysogenum. Microorganism heat capacities below 10 K were best described by an expanded Debye-T³ law. Based on the collected data, empirical formulas and entropies per C-mole of the analyzed organisms were determined. The measured heat capacities were compared to predictions of Kopp's rule and Hurst-Harrison equation, both of which were found to be able to give reasonably accurate predictions. The determined entropies were compared to predictions of Battley and Roels models. The Battley model was found to be more accurate. The measured microorganism entropies lay between the values of their principal macromolecular constituents: DNA, and globular and fibrillar proteins. This indicates that self-assembly of the macromolecular components into cellular structures does not lead to decrease in thermal entropy., (Copyright © 2021 Elsevier B.V. All rights reserved.)

The nature of an interfacial structure buried within a device assembly is often critical to its function. For example, the dye/TiO 2 interfacial structure that comprises the working electrode of a dye-sensitized solar cell (DSC) governs its photovoltaic output. These structures have been determined outside of the DSC device, using ex situ characterization methods; yet, they really should be probed while held within a DSC since they are modulated by the device environment. Dye/TiO 2 structures will be particularly influenced by a layer of electrolyte ions that lies above the dye self-assembly. We show that electrolyte/dye/TiO 2 interfacial structures can be resolved using in situ neutron reflectometry with contrast matching. We find that electrolyte constituents ingress into the self-assembled monolayer of dye molecules that anchor onto TiO 2 . Some dye/TiO 2 anchoring configurations are modulated by the formation of electrolyte/dye intermolecular interactions. These electrolyte-influencing structural changes will affect dye-regeneration and electron-injection DSC operational processes. This underpins the importance of this in situ structural determination of electrolyte/dye/TiO 2 interfaces within representative DSC device environments.

We report multiple magnetic phase transitions and critical behavior of the 2D charge-density wave compound TbTe 3 studied by μSR measurements and dc magnetization measurements. Zero-field μSR has shown three magnetic transitions below 7 K. The longitudinal field measurements under 50 G has confirmed the first transition at T N = 6.3 K. Scaling analysis from above T N gives the critical exponent w = 0.63(5), suggesting the Ising 3D antiferromagnetic nature of the ordering, which is likely mediated by the 2D correlations. However, the obtained w = 0.81(5) below T N indicates the ferromagnetic phase, which arises over the multiphase transitions at lower temperatures. Temperature-dependent transverse frequency shift gives a relatively smaller exponent γ = 1.0(1) than the Ising 3D model. The different transitions were also observed by dc magnetization measurements, suggesting two magnetic transitions at 7.4 K and 3.1 K, which correspond to the antiferromagnetic and ferromagnetic phases respectively.

Several different mechanisms of magnetoresistance (MR) have been observed in 1111 LnMnAsO 1- x F x oxypnictides (Ln = lanthanide) as a result of magnetic coupling between the Mn and Ln. Such phases also exhibit interesting magnetic phase transitions upon cooling. Sr 2 Mn 2 CrAs 2 O 2 has been synthesized to investigate if it is possible to observe MR and/or magnetic phase transitions as a result of magnetic coupling between the Mn and Cr. Sr 2 Mn 2 CrAs 2 O 2 crystallizes in the tetragonal space group I 4/ mmm containing alternating MO 2 2- and M' 2 As 2 2- layers, and neutron diffraction results demonstrate that the actual stoichiometry is Sr 2 Mn 2.23 Cr 0.77 As 2 O 2 . Cation order is present between Mn and Cr, with Cr predominantly occupying the square planar MO 2 2- site. Below 410 K, the magnetic moments of the Mn/Cr ions in the M' 2 As 2 2- sublattice exhibit G-type antiferromagnetic order. The Mn/Cr moments within the MO 2 2- layer order below 167 K with a K 2 NiF 4 -type antiferromagnetic structure that simultaneously induces a spin flip of the magnetic moments in the M' 2 As 2 2- layers from a G-type to a C-type antiferromagnetic arrangement. The results demonstrate that the superexchange interactions are finely balanced in Sr 2 Mn 2.23 Cr 0.77 As 2 O 2 . Sr 2 Mn 2.23 Cr 0.77 As 2 O 2 is semiconducting, and there is no evidence of MR.

Here we report a high-pressure investigation into the structural and magnetic properties of the double perovskite La 2 NiMnO 6 using neutron scattering over a temperature range of 4.2-300 K at ambient pressure and over a temperature range of 120-1177 K up to a maximum pressure of 6.6 GPa. X-ray diffraction was also used up to a maximum pressure of 64 GPa, over a temperature range of 300-720 K. The sample was found to exist in a mixed rhombohedral/monoclinic symmetry at ambient conditions, the balance of which was found to be strongly temperature- and pressure-dependent. Alternating current magnetometry and X-ray absorption near-edge structure measurements were made at ambient pressure to characterize the sample, suggesting that the transition-metal sites exist in a mixed Ni 3+ /Mn 3+ and Ni 2+ /Mn 4+ state at ambient temperature and pressure. Analysis of the magnetic properties of the sample shows that the Curie temperature can be enhanced by ∼12 K with 2 GPa applied pressure, but it is highly stable at pressures beyond this. We report a pressure-volume-temperature equation of state for this material over this combined temperature and pressure range, with an ambient temperature bulk modulus of ∼179(8) GPa. The previously reported transition from monoclinic to rhombohedral symmetry upon heating to 700 K is seen to be encouraged with applied pressure, transforming fully by ∼1.5 GPa. Raman spectroscopy data were collected up to ∼8 GPa and show no clear changes or discontinuities over the reported phase transition to rhombohedral symmetry or any indication of further changes over the range considered. The ambient-pressure Grüneisen parameter γ th was determined to be γ th = 2.6 with a Debye temperature of 677 K. The individual modal parameters γ j at ambient temperature were also determined from the high-pressure Raman data.

The isostructural double perovskites Ba 2 CuTeO 6 and Ba 2 CuWO 6 are shown by theory and experiment to be frustrated square-lattice antiferromagnets with opposing dominant magnetic interactions. This is driven by differences in orbital hybridisation of Te 6+ and W 6+ . A spin-liquid-like ground state is predicted for Ba 2 Cu(Te 1-x W x )O 6 solid solution similar to recent observations in Sr 2 Cu(Te 1-x W x )O 6 .

Reaction of activated germanium with nBu2Te2 in THF solution was shown to be more effective for the preparation of the germanium(iv) tellurolate compound, [Ge(TenBu)4], than reaction of GeCl4 with LiTenBu in a 1 : 4 molar ratio in THF. The product was characterised by 1H, 13C{1H} NMR spectroscopy and microanalysis and evaluated as a single source precursor for the low pressure chemical vapour deposition of GeTe thin films. Depending upon deposition conditions, either dull grey films (predominantly elemental Te) or highly reflective (GeTe) films were obtained from the pure precursor. Grazing incidence X-ray diffraction shows that the highly reflective films are comprised of the rhombohedral α-GeTe phase, while scanning electron microscopy and energy dispersive X-ray analysis reveal rhomb-shaped crystallites with a 49(1) : 51(1)% Ge : Te ratio. This structure is also confirmed from Raman spectra. Van der Pauw measurements show ρ = 3.2(1) × 10-4 Ω cm and Hall electrical measurements indicate that the GeTe thin films are p-type, with a mobility of 8.4(7) cm2 V-1 s-1 and carrier concentration of 2.5(2) × 1021 cm-3. The high p-type concentration is most likely a result of the substantial Ge vacancies in its sub-lattice, in line with the EDX elemental ratios.

The colossal magnetoresistance (CMR) observed in the oxypnictide NdMnAsO1-xFx has been further investigated. The magnetotransport is dominated by magnetopolarons. Magnetoresistance measurements of the series Nd(Mn1-xCox)AsO0.95F0.05 show that doping with cobalt on the manganese site pins the magnetopolarons and suppresses the CMR, which is completely destroyed by x = 0.047. The chemical doping results in non-stoichiometric samples, with both As and O vacancies. The relationship between the non-stoichiometry, magnetic order, electron doping and CMR is explored. The Nd antiferromagnetic transition and simultaneous reorientation of the Mn spins into the basal plane at 23 K (TSR) is not effected by Co doping. However, there is a significant decrease in TN(Mn) as the antiferromagnetic transition is suppressed from 360 K to 300 K as x increases from 0-0.047. The manganese moment at 10 K is also reduced from 3.86(2)μB to 3.21(2)μB over the same doping range. This reduction in the in-plane Mn moment decreases the electron-electron correlations below TSR and acts to further diminish the magnetoresistance.

The molecular Sn(iv) complexes, [SnCl 4 { n BuS(CH 2 ) 3 S n Bu}] (2), [SnCl 4 ( n Bu 2 S) 2 ] (3) and [SnCl 4 ( n Bu 2 Se) 2 ] (4) have been prepared in good yield from reaction of SnCl 4 with the appropriate chalcogenoether ligand in anhydrous hexane and, together with the known [SnCl 4 { n BuSe(CH 2 ) 3 Se n Bu}] (1), employed as single source precursors for the low pressure chemical vapour deposition of the corresponding tin dichalcogenide thin films. At elevated temperatures the bidentate ligand precursors, (1) and (2), also form the tin monochalcogenides, SnSe and SnS, respectively. In contrast, (3) gave a mixture of phases, SnS 2 , Sn 2 S 3 and SnS and (4) gave SnSe 2 only. The morphologies, elemental compositions and crystal structures of the resulting films have been determined by scanning electron microscopy, energy dispersive X-ray spectroscopy, grazing incidence X-ray diffraction and Raman spectroscopy. Van der Pauw measurements on the SnS 2 , SnS and SnSe 2 films confirm their resistivities to be 2.9(9), 266(3) and 4.4(3) Ω cm, respectively.

The structural and magnetic properties of LaCo 0.9 Mn 0.1 O 3 have been studied as a function of pressure by neutron powder diffraction and DC magnetometry. The material is confirmed to exhibit rhombohedral R [Formula: see text] c symmetry between ambient pressure and 6 GPa. We have determined the bulk modulus B 0 of the sample using a second-order Birch-Murnaghan equation of state which yielded: B 0   =  140(9) GPa and V [Formula: see text]. We report a non-linear increase of the Curie temperature T C from an ambient pressure value of 224.7 K to  ∼236 K at a pressure of 4 GPa. Finally, we confirm the glassy-like nature of the magnetism in LaCo 0.9 Mn 0.1 O 3 , which is maintained throughout the pressure range explored.

Ca 2 Mn 3 O 8 exhibits a complex layered structure comprised of Mn 3 O 8 4- layers separated by Ca 2+ ions. In contrast with the more traditional triangular delafossite layered materials the Mn 3 O 8 4- layers additionally exhibit an ordered vacancy, which forms a 'bow-tie' like arrangement of the Mn 4+ ions. We report a comprehensive study of the magnetic properties of a series of Ca 2 Mn 3 O 8 materials with different morphologies. EXAFS and XANES analysis confirm no differences in either manganese environment or oxidation state between materials. Apparent differences in magnetic order from SQUID magnetometry can be rationalised by uncompensated surface spins arising as a result of changes to the surface to volume ratio between morphologies. Furthermore, these data suggest these materials are potentially frustrated in nature, due to the triangular connectivity of Mn 4+ spins, with a simple 'spin-up/spin-down' (↑↓) antiferromagnetic model unable to explain the data collected.