Magnetic Stimulation for Programmed Shape Morphing: Review of Four-Dimensional Printing, Challenges and Opportunities.

In the field of Additive Manufacturing, four-dimensional (4D) printing has emerged as a promising technique to fabricate smart structures capable of undergoing shape morphing in response to specific stimuli. Magnetic stimulation offers a safe, remote, and rapid actuation mechanism for magnetically responsive structures. This review provides a comprehensive overview of the various strategies and manufacturing approaches employed in the development of magnetically stimulated shape morphing 4D-printed structures, based on an extensive literature search. The review explores the use of magnetic stimulation either individually or in combination with other stimuli. While most of the literature focuses on single-stimulus responsive structures, a few examples of multi-stimuli responsive structures are also presented. We investigate the influence of the orientation of magnetic particles in smart material composites, which can be either random or programmed during or after printing. Finally, the similarities and differences among the different strategies and their impact on the resulting shape-morphing behavior are analyzed. This systematic overview functions as a guide for readers in selecting a manufacturing approach to achieve a specific magnetically actuated shape-morphing effect.

Kinetic energy driven two-sublattice double-exchange: a general mechanism of magnetic exchange in transition metal compounds.

One of the most important phenomena in magnetism is the exchange interaction between magnetic centers. In this topical review, we focus on the exchange mechanism in transition-metal compounds and establish kinetic-energy-driven two-sublattice double-exchange as a general exchange mechanism, in addition to well-known mechanisms like superexchange and double exchange. This mechanism, which was first proposed [Phys. Rev. Lett. {\bf 85}, 2549 (2000)], in the context of Sr$_2$FeMoO$_6$, a  double-perovskite compound, later found to describe a large number of 3d and 4d or 5d transition metal-based double perovskites. The magnetism in  multi-sublattice magnetic systems like double-double and quadrupolar perovskites involving 3d and 4d or 5d transition-metal ions have also been found to be governed by this as a primary mechanism of exchange.  For example, the numerical solution of a two-sublattice double exchange with additional superexchange couplings for the FeRe-based double double and quadrupolar perovskites are found to reproduce the experimentally observed magnetic ground state as well as the high transition temperature of above 500 K. The applicability of this general mechanism extends beyond the  perovskite crystal structures, and oxides, as demonstrated for the pyrochlore oxide, Tl$_2$Mn$_2$O$_7$ and the square-net chalcogenides KMnX$_2$ (X=S, Se, Te). The counter-intuitive doping dependence and pressure effect of magnetic transition temperature in Tl$_2$Mn$_2$O$_7$ is explained, while KMnX$_2$ (X=S, Se, Te) compounds are established as half-metallic Chern metals guided by two sublattice double exchange. While the kinetic energy-driven two-site double-exchange mechanism was originally proposed to explain ferromagnetism, a filling-dependent transition can lead to a rare situation of the antiferromagnetic metallic ground state, as found in La-doped Sr$_2$FeMoO$_6$, and proposed for computer predicted double perovskites Sr(Ca)$_2$FeRhO$_6$. This opens up a vast canvas to explore.

Deciphering competing interactions of Kitaev-Heisenberg-\texorpdfstring{$\Gamma$} system in clusters: part II - dynamics of Majorana fermions.

We perform a systematic and exact study of Majorana fermion dynamics in the Kitaev-Heisenberg-$\Gamma$ model in a few finite-size clusters increasing in size up to twelve sites. We employ exact Jordan-Wigner transformations to evaluate certain measures of Majorana fermion correlation functions, which effectively capture matter and gauge Majorana fermion dynamics in different parameter regimes. An external magnetic field is shown to produce a profound effect on gauge fermion dynamics. Depending on certain non-zero choices of other non-Kitaev interactions, it can stabilise it to its non-interacting Kitaev limit. For all the parameter regimes, gauge fermions are seen to have slower dynamics, which could help build approximate decoupling schemes for appropriate mean-field theory. The probability of Majorana fermions returning to their original starting site shows that the Kitaev model in small clusters can be used as a test bed for the quantum speed limit.

Structure and properties of mixed valent CeFe2Al8.

Temperature dependent magnetic, electrical transport and thermal properties of polycrystalline orthorhombic CeFe2Al8intermetallic compound have been studied along with its isostructural La counterpart, LaFe2Al8. For the cerium compound, low field dc magnetization exhibits an antiferromagnetic like ordering (TN) ~ 4 K. The main feature of the magnetic susceptibility plot is a broad hump spanning a large temperature range, indicating mixed valence of Ce in the compound, in good agreement with reported literature. However, contrary to the reported observations we find that the mixed valence state is very robust and was evident even up to very high magnetic fields (> 2 T). Further, in this work we report 3d core level photoemission spectra of cerium in CeFe2Al8, to understand the valence state of cerium ions in this system. Additionally, from resistivity measurements it is found that, CeFe2Al8is metallic with no indication of any anomaly, till the lowest temperature of measurement. Specific heat measurements show very low value of heat capacity and electronic contribution. The isostructural La analogue, LaFe2Al8compound shows broadness in susceptibility with maxima around 44 K which may be attributed to ordering of Fe moments. The comparison of Ce and La compounds brings out the role of Fe magnetic moments which may be responsible for competing with cerium moments and resulting in the dilution of long-range magnetic order, also contributing to magnetic frustration in CeFe2Al8. .

Imaging Strain-Controlled Magnetic Reversal in Thin CrSBr.

Two-dimensional materials are extraordinarily sensitive to external stimuli, making them ideal for studying fundamental properties and for engineering devices with new functionalities. One such stimulus, strain, affects the magnetic properties of the layered magnetic semiconductor CrSBr to such a degree that it can induce a reversible antiferromagnetic-to-ferromagnetic phase transition. Using scanning SQUID-on-lever microscopy, we directly image the effects of spatially inhomogeneous strain on the magnetization of layered CrSBr, as it is polarized by a field applied along its easy axis. The evolution of this magnetization and the formation of domains is reproduced by a micromagnetic model, which incorporates the spatially varying strain and the corresponding changes in the local interlayer exchange stiffness. The observed sensitivity to small strain gradients along with similar images of a nominally unstrained CrSBr sample suggest that unintentional strain inhomogeneity influences the magnetic behavior of exfoliated samples.

Stabilization of the Compressed Planar Benzene Dianion in Inverse-Sandwich Rare Earth Metal Complexes.

For the first time, the capture of a planar antiaromatic benzene dianion in between two trivalent rare earth (RE) metal cations, each stabilized by two guanidinate ligands, is reported. The synthesized inverse-sandwich complexes [{(Me3Si)2NC(NiPr)2}2RE]2(µ-ƞ6:ƞ6-C6H6), (RE = Y (1), Dy (2), and Er (3)) feature a remarkably planar benzene dianion, previously not encountered for any metal ion prone to low or absent covalency. The -2 charge localization at the benzene ligand was deduced from the results obtained by single-crystal X-ray diffraction analyses, spectroscopy, magnetometry, and Density Functional Theory (DFT) calculations. In the 1H NMR spectrum of the diamagnetic Y complex 1, the equivalent proton resonance of the bridging benzene dianion ligand is drastically shifted to higher field in comparison to free benzene. This and the calculated highly positive Nucleus-Independent Chemical Shift (NICS) values are attributed to the antiaromatic character of the benzene dianion ligand.  The crucial role of the ancillary guanidinate ligand scaffold in stabilizing the planar benzene dianion conformation was also elucidated by DFT calculations. Remarkably, the planarity of the benzene dianion originates from the stabilization of the π-type orbitals of the d-manifold and compression through its strong electrostatic interaction with the two REIII sites.

Magnetic response and bioaccessibility of toxic metal pollution in outdoor dustfall in Shanghai, China.

Toxic metal content testing, environmental magnetic monitoring and in vitro bioaccessibility experiments each have their own advantages and are often used independently for environmental monitoring, but there are few studies that combine the three to evaluate the hazards of toxic metals to humans. This paper investigated the total content, magnetic properties and bioaccessibility of nine potentially toxic metal elements (Zn, Sn, Pb, Cu, Fe, Ni, Cr, Sr, Mn) in dustfall from different functional zones in Shanghai, China, and systematically compared the related results. The results show that these nine metal elements have different degrees of contamination and enrichment in outdoor dustfall, and their content distribution shows the following trend: Zn>Sn>Pb>Cu>Fe>Ni>Cr>Sr>Mn. Magnetic characteristics χlf and SIRM are mostly positively correlated with the metal elements, indicating that the higher the content of magnetic minerals in the sample, the higher the concentration of metal elements. It was also found that χlf, SIRM, and χARM can well reflect the characteristics of dustfall pollution. The magnetic minerals have a certain degree of enrichment, and the particle size of the magnetic minerals is relatively coarse, mainly in the form of coarse multi-domain and pseudo-single-domain particles, which are largely derived from anthropogenic pollution. The χlf and PM10 concentrations in the precipitation show relatively similar spatial trends, so χlf, SIRM, and χARM can be used as air pollution indices to facilitate the evaluation of metal elements pollution in dustfall. The overall trend in gastric bioaccessibility is Pb>Zn>Mn>Cu>Cr. Due to the increase in the pH of digestive fluid, the bioavailability of toxic metals decreases significantly from the gastric stage to the intestinal stage. χlf, SIRM, and χARM/SIRM are all related to the bioaccessibility of toxic metals in the intestinal stage, so they can be used as toxicity indicators to evaluate the bioaccessibility of toxic metals in dustfall.

Fundamental Theory of Current-Induced Motion of Magnetic Skyrmions.

Magnetic skyrmions are topological spin textures that appear in magnets with broken spatial inversion symmetry as a consequence of competition between the ferromagnetic exchange interactions and the Dzyaloshinskii-Moriya interactions in a magnetic field. In the research of spintronics, the current-driven dynamics of skyrmions has been extensively studied aiming at their applications to next-generation spintronic devices. However, current-induced skyrmion motion exhibits diverse behaviors depending on various factors and conditions such as the type of skyrmion, driving mechanism, system geometry, direction of applied current, and type of the magnet. While this variety attracts enormous research interest of fundamental science and enriches the possibilities of technical applications, it is also a source of difficulty and complexity that hinders their comprehensive understandings. In this article, we discuss fundamental and systematic theoretical descriptions of current-induced motion of skyrmions driven by the spin-transfer torque and the spin-orbit torque. Specifically, we theoretically describe the behaviors of current-driven skyrmions depending on the factors and conditions mentioned above by means of analyses using the Thiele equation. Furthermore, the results of the analytical theory are visually demonstrated and quantitatively confirmed by micromagnetic simulations using the Landau-Lifshitz-Gilbert-Slonczewski equation. In particular, we discuss dependence of the direction and velocity of motion on the type of skyrmion (Bloch type and Néel type), the system geometry (thin plate and nanotrack), the direction of applied current (length and width direction of the nanotrack), and the type of magnet (ferromagnet and antiferromagnet). The comprehensive theory provided by this article is expected to contribute significantly to research on the manipulation and control of magnetic skyrmions by electric currents for future spintronics applications.spintronics applications. .

Pressure-induced magnetic and topological transitions in non-centrosymmetric MnIn2Te4.

In recent years, the study of magnetic topological materials, with their variety of exotic physics, has significantly flourished. In this work, we predict the interplay of magnetism and topology in the non-centrosymmetric ternary manganese compound MnIn2Te4under external hydrostatic pressure, using first-principles calculations and symmetry analyses. At ambient pressure, the ground state of the system is an antiferromagnetic insulator. With the application of a small hydrostatic pressure (∼0.50 GPa), it undergoes a magnetic transition, and the ferromagnetic state becomes energetically favorable. At ∼2.92 GPa, the ferromagnetic system undergoes a transition into a Weyl semimetallic phase, which hosts multiple Weyl points in the bulk. The presence of non-trivial Weyl points have been verified by Wilson bands computations and the presence of characteristic surface Fermi arcs. Remarkably, we discover that the number of Weyl points in this system can be controlled by pressure and that these manifest in an anomalous Hall conductivity (AHC). In addition to proposing a new candidate magnetic topological material, our work demonstrates that pressure can be an effective way to induce and control topological phases, as well as AHC, in magnetic materials. These properties may allow our proposed material to be used as a novel pressure-controlled Hall switch.

Response functions for electric field induced two-dimensional nonlinear spectroscopy in a Kitaev magnet.

We study the dynamical response functions relevant for electric field induced two-dimensional (2D) coherent nonlinear optical spectroscopy in a Kitaev magnet at finite temperature. We show that these response functions are susceptible to both types of fractional quasiparticles of this quantum spin-liquid, i.e. fermions and flux visons. Focusing on the second order response, we find a strong antidiagonal feature in the 2D frequency plane, related to the galvanoelectric effect of the fractional fermions. Perpendicular to the antidiagonal, the width of this feature is set by quasiparticle relaxation rates beyond the bare Kitaev magnet, thereby providing access to single-particle characteristics within a multi-particle continuum. While the 2D spectrum of the response is set by the fermionic quasiparticles and displays Fermi blocking versus temperature, the emergent bond randomness which arises due to thermally populated visons strongly modifies the fermionic spectrum. Therefore also the presence of gauge excitations is manifest in the 2D nonlinear response as the temperature is increased beyond the flux proliferation crossover.

Integration of interpretable machine learning and environmental magnetism elucidates reduction mechanism of bioavailable potentially toxic elements in lakes after monsoon.

Little information is available on the influence of substantial precipitation and particulate matter entering during the monsoon process on the release of potentially toxic elements (PTEs) into lake sediments. Sediments from a typical subtropical lake across three periods, pre-monsoon, monsoon, and post-monsoon, were collected to determine the chemical forms of 12 PTEs (As, Cd, Co, Cr, Cu, Fe, Hg, Pb, Mn, Ni, Sb, and Zn), magnetic properties, and physicochemical indicators. Feature importance, Shapley additive explanations, and partial dependence plots were used to explore the factors influencing bioavailable PTEs. The proportion of bioavailable forms of PTEs decreased from 3.85 % (Cd) to 87.84 % (Hg) after the monsoon. Gradient extreme boosting demonstrated robust fitting accuracy for the prediction of the bioavailable forms of the 12 PTEs (R2 > 0.84). Shapley additive explanations identified that the bioavailable forms were influenced by the total PTE concentrations, wind, shortwave radiation, and particle inputs (25.1 %-88.5 % for total importance), either individually or in combination. The partial dependence plots highlighted the influence thresholds of background values and anthropogenic factors on the bioavailable forms of PTEs. Changes in environmental properties could indicate the process of external sediment influx into lakes. The optimized model combined with magnetic parameters showed strong performance in other cases (coefficient of determination>0.58), confirming the ubiquitous decrease in bioavailable forms of PTEs in sediments across subtropical lakes after monsoons.

Tuning the Spin Interaction in Nonplanar Organic Diradicals through Mechanical Manipulation.

Open-shell polycyclic aromatic hydrocarbons (PAHs) represent promising building blocks for carbon-based functional magnetic materials. Their magnetic properties stem from the presence of unpaired electrons localized in radical states of π character. Consequently, these materials are inclined to exhibit spin delocalization, form extended collective states, and respond to the flexibility of the molecular backbones. However, they are also highly reactive, requiring structural strategies to protect the radical states from reacting with the environment. Here, we demonstrate that the open-shell ground state of the diradical 2-OS survives on a Au(111) substrate as a global singlet formed by two unpaired electrons with antiparallel spins coupled through a conformational-dependent interaction. The 2-OS molecule is a "protected" derivative of the Chichibabin's diradical, featuring a nonplanar geometry that destabilizes the closed-shell quinoidal structure. Using scanning tunneling microscopy (STM), we localized the two interacting spins at the molecular edges, and detected an excited triplet state a few millielectronvolts above the singlet ground state. Mean-field Hubbard simulations reveal that the exchange coupling between the two spins strongly depends on the torsional angles between the different molecular moieties, suggesting the possibility of influencing the molecule's magnetic state through structural changes. This was demonstrated here using the STM tip to manipulate the molecular conformation, while simultaneously detecting changes in the spin excitation spectrum. Our work suggests the potential of these PAHs as all-carbon spin-crossover materials.

Rolling Motion of Rigid Skyrmion Crystallites Induced by Chiral Lattice Torque.

Magnetic skyrmions are topologically protected spin textures with emergent particle-like behaviors. Their dynamics under external stimuli is of great interest and importance for topological physics and spintronics applications alike. So far, skyrmions are only found to move linearly in response to a linear drive, following the conventional model treating them as isolated quasiparticles. Here, by performing time and spatially resolved resonant elastic X-ray scattering of the insulating chiral magnet Cu2OSeO3, we show that for finite-sized skyrmion crystallites, a purely linear temperature gradient not only propels the skyrmions but also induces continuous rotational motion through a chiral lattice torque. Consequently, a skyrmion crystallite undergoes a rolling motion under a small gradient, while both the rolling speed and the rotational sense can be controlled. Our findings offer a new degree of freedom for manipulating these quasiparticles toward device applications and underscore the fundamental phase difference between the condensed skyrmion lattice and isolated skyrmions.

Synthesis and properties of Sr2La2NiW2O12, a new S = 1 triangular lattice magnet.

Magnetic materials featuring triangular arrangements of spins are frequently investigated as platforms hosting magnetic frustration. Hexagonal perovskites with ordered vacancies serve as excellent candidates for two-dimensional triangular magnetism due to the considerable separation of the magnetic planes. In this work, the effects of chemical pressure on the ferromagnetic ground state of Ba2La2NiW2O12 by substitution of Ba2+ with Sr2+ to produce Sr2La2NiW2O12 are investigated. The two materials are characterized using synchrotron-based XRD, XANES and EXAFS in addition to magnetometry in order to correlate their crystal structures and magnetic properties. Both materials form in space group R3, yet as a result of the enhanced bending of key bond angles due to the effects of chemical pressure, the TC value of the magnetic Ni2+ sublattice is reduced from ∼6 K in Ba2La2NiW2O12 to 4 K in Sr2La2NiW2O12.

Analysis of magnetic structures in JANA2020.

JANA2020 is a program developed for the solution and refinement of regular, twinned, modulated, and composite crystal structures. In addition, JANA2020 also includes a magnetic option for solving magnetic structures from powder and single-crystal neutron diffraction data. This tool uses magnetic space and superspace symmetry to describe commensurate and incommensurate magnetic structures. The basics of the underlying formulation of magnetic structure factors and the use of magnetic symmetry for handling modulated and non-modulated magnetic structures are presented here, together with the general features of the magnetic tool. Examples of structures solved in the magnetic option of JANA2020 are given to illustrate the operation and capabilities of the program.

High-pressure synthesis and characterizations of a new ternary Ce-based compound Ce3TiAs5.

We report the structure and properties of a new Ce-based compound Ce3TiAs5synthesized under high-pressure and high-temperature conditions. It crystallizes in a hexagonal Hf5Sn3Cu-anti type structure with zig-zag like Ce chains along thecaxis. This compound is metallic and undergoes a magnetic phase transition atTN= 13 K. A metamagnetic transition occurs at ∼0.7 T. The Sommerfeld coefficient for the compound is determined to be about 215 mJ/(Ce-mol*K2), demonstrating a heavy Fermion behavior. The resistivity is featured with two humps, which arises from the synergistic effect of crystal electric field and magnetic scattering. The magnetic ordering temperatureTNgradually increases in the sequence of Ce3TiPn5with Pn = Bi, Sb, and As, which implies that the Ruderman-Kittel-Kasuya-Yosida interaction should be still predominant in Ce3TiAs5.

Biodistribution of iron oxide tattoo pigment: An experimental murine study.

Tattoo pigment is expected to migrate beyond the skin to regional lymph nodes and the liver. Modern tattoo ink commonly contains metals that may pose a clinical problem during MRI examinations. This study aimed to investigate the biodistribution of iron oxide pigment to internal organs in mice. Moreover, when exposed to a static magnetic field, we studied whether any reactions followed in the tattooed skin. Twenty-seven hairless C3.Cg-Hrhr/TifBomTac mice were included; 20 were tattooed with iron oxide ink in a rectangular 3 cm2 pattern; seven were controls. Ten of the tattooed mice were exposed to a 3 T MRI scanner's static magnetic field. Following euthanasia, evaluations of dissected organs involved MRI T2*-mapping, light microscopy (LM) and metal analysis. T2*-mapping measures the relaxation times of hydrogen nuclei in water and fat, which may be affected by neighbouring ferrimagnetic particles, thus enabling the detection of iron oxide particles in organs. Elemental analysis detected a significant level of metals in the tattooed skin compared to controls, but no skin reactions occurred when exposed to a 3 T static magnetic field. No disparity was observed in the liver samples with metal analysis. T2* mapping found no significant difference between the two groups. Only minute clusters of pigment particles were observed in the liver by LM. Our results demonstrate a minimal systemic distribution of the iron oxide pigments to the liver, whereas the kidney and brain were unaffected. The static magnetic field did not trigger skin reactions in magnetic tattoos but may induce image artefacts during MRI.

Facile microwave synthesis of various-shaped magnetite/ reduced graphene oxide heterostructures and their magnetization properties.

Heterostructures of magnetite (Fe3O4) nanoparticles and reduced graphene oxide (RGO) sheets are very common composite materials for different applications such as catalysis, energy storage, and biomedicine. Developing methods for the facile control of the size and shape of both freestanding Fe3O4 nanoparticles and those anchored onto RGO sheets is in demand. Herein, we report on the rapid and facile microwave synthesis (MWS) of Fe3O4 nanoparticles and Fe3O4/RGO with various sizes and shapes using the oleylamine (OAm)/oleic acid (OAc) ligand pair. The solvothermal synthesis using microwave irradiation (MWI) resulted in the concurrent conversion of graphene oxide (GO) into RGO and the in-situ formation of various-shaped Fe3O4 on RGO sheets. Freestanding Fe3O4 nanoparticles of various shapes were prepared using MWS for comparison. The morphological, structural, and surface properties of the samples were studied using different characterization techniques. The magnetization properties of the prepared samples were determined using a vibrating sample magnetometer. Various-shaped standalone and RGO-supported Fe3O4 nanoparticles including nanospheres, nanocubes, and nanotriangles were synthesized via MWI at 1000 W for 20 min by changing the ratios of the iron precursor and the OAm/OAc ligand pair. Interestingly, the MWI using OAm/OAc ligand pair of a molar ratio of 3:4 resulted in the in-situ formation of large hexagonal Fe3O4/RGO. The X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results confirm the crystallinity and spinel structure of the prepared Fe3O4 samples and prove the concurrent conversion of GO into RGO with assemblies of Fe3O4 nanoparticles. The magnetization measurements further emphasized the role of size and shape in affecting the magnetic properties of Fe3O4 and Fe3O4/RGO heterostructures. The results identify the qualities of the prepared samples and prove the MWS as a facile one-pot method for the preparation of Fe3O4 and Fe3O4/RGO heterostructures.

Air-microwave simultaneously induced carbon fiber surface oxidation and magnetism adjustment by CoOx nanoparticles rapid assembly for interface enhancement and electromagnetic wave absorption of its composites.

It is a significant challenge to develop a fast carbon fiber (CF) surface modification method, especially for the high strength electromagnetic wave (EMW) absorption materials. Herein, magnetic CoOx nanoparticles are successfully synthesized and uniformly assembled on CF surface with high oxygen-containing groups by rapid ambient microwave carbon thermal shock (MCTS). The presence of oxygen defect sites on CF surface promotes CoOx nanoparticles nucleation. The number of oxygen defects and the types of magnetic nanoparticles on the CF surface effectively adjust the surface chemical activity and the electromagnetic properties of CF, which is conducive to improving the EMW absorption performance and interface compatibility of the CoOx nanoparticles modified CF reinforced polyamide 6 (CO@CF/PA6) composites. Compared with CO@CF-0 s/PA6, the tensile strength and modulus of CO@CF-3.5 s/PA6 composite are increased by 18.1 % and 18.6 %, respectively. It also displays a minimum reflection loss value (-59.9 dB) at a thinner thickness of 1.9 mm while the maximum effective absorption bandwidth reaches 5.02 GHz with a thickness of 1.8 mm. Its radar cross-section values exhibit less than -10 dBm2 at all tested detection angles. This rapid MCTS shows great potential for large-scale production of CF modification with low-cost, efficient and environmentally friendly process.

Coexistence of multiple magnetic interactions in oxygen-deficient V2O5 nanoparticles.

This paper reports on the spin glass-like coexistence of competing magnetic orders in oxygen-deficient V2O5 nanoparticles with a broad size distribution. X-ray photoelectron spectroscopy yields the surface chemical stoichiometry of nearly V2O4.65 due to significant defect density. Temperature-dependent electrical conductivity and thermopower measurements demonstrate a polaronic conduction mechanism with a hopping energy of about 0.112 eV. The V2O5-δ sample exhibits strong field as well as temperature-dependent magnetic behaviour when measured with a SQUID magnetometer, showing positive magnetic susceptibility across the temperature range of 2-350 K. Field-cooled and zero-field-cooled data indicate hysteresis, suggesting glassy behaviour. The formation of small polarons due to oxygen vacancy defects, compensated by V4+ charge defects, results in Magneto-Electronic Phase Separation (MEPS) and various magnetic exchanges, as predicted by first-principle calculations. This is evidenced by the strong hybridisation of V orbitals in the vicinity of vacant oxygen site. An increase in V4+ defects shows an antiferromagnetic (AFM) component. The magnetic diversity in undoped V2O4.9 originates from defect density and their random distribution, leading to MEPS. This involves localised spins in polarons and ferromagnetic (FM) clusters on a paramagnetic (PM) background, while V4+ dimers induce AFM interactions. Electron paramagnetic resonance spectra measured at different temperatures indicate a dominant paramagnetic signal at a g-value of 1.97 due to oxygen defects, with a broad FM resonance-like hump. Both signals diminish with increasing temperature. Neutron diffraction data rules out long-range magnetic ordering, reflecting the composition as V2O4.886. Despite the FM hysteresis, no long-range order is observed in neutron diffraction data, consistent with the polaron cluster-like FM with MEPS nature. This detailed study shall advance the understanding of the diverse magnetic behaviour observed in undoped non-magnetic systems.