Condensed Matter

28 pages, 2121 KB

Open AccessArticle

Using Machine-Learned Force Fields for Describing Heat-Transport-Related Quantities in AlGaN and Derived Materials

by Simon Fernbach, Egbert Zojer and Natalia Bedoya-Martínez

Condens. Matter 2026, 11(2), 23; https://doi.org/10.3390/condmat11020023 - 11 Jun 2026

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In this work, we develop machine-learned moment tensor potentials (MTPs) to simulate the static and dynamic structural properties in Al_xGa_1−xN and related materials. The potentials are trained on DFT-calculated data for forces, stresses, and energies obtained from random [...] Read more.

In this work, we develop machine-learned moment tensor potentials (MTPs) to simulate the static and dynamic structural properties in Al_xGa_1−xN and related materials. The potentials are trained on DFT-calculated data for forces, stresses, and energies obtained from random atomic displacements and cell deformations. MTP-calculated physical properties, including lattice parameters and elastic constants, thermal expansion, harmonic and anharmonic vibrational properties, and the thermal conductivity, are benchmarked against first-principles results and experimental data. The comparisons testify to the very high accuracy achieved by the machine-learned potentials despite the massively reduced computational effort. Additionally, the impact of various aspects of the MTP training procedure is examined. Full article

(This article belongs to the Special Issue 10th Anniversary of Condensed Matter: Recent Advances in Condensed Matter Physics)

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8 pages, 195 KB

Open AccessOpinion

The Universe Observed with Particle Detectors: Astrophysical Legacy of Guido Barbiellini Amidei

by Roberto Capuzzo Dolcetta

Condens. Matter 2026, 11(2), 22; https://doi.org/10.3390/condmat11020022 - 8 Jun 2026

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Abstract

The development of modern high-energy astrophysics has been deeply intertwined with advances in particle detector technology. Guido Barbiellini Amidei (1943–2024) played a pivotal role in bridging experimental particle physics and astrophysical observation. His scientific career spanned over four decades, from early electron–positron collider [...] Read more.

The development of modern high-energy astrophysics has been deeply intertwined with advances in particle detector technology. Guido Barbiellini Amidei (1943–2024) played a pivotal role in bridging experimental particle physics and astrophysical observation. His scientific career spanned over four decades, from early electron–positron collider experiments at ADONE and LEP (DELPHI) to space-based missions such as AGILE, Fermi, and PAMELA. This memorial paper reviews the evolution of high-energy astrophysics as a detector-driven science, highlighting key domains where Barbiellini left an indelible mark: gamma-ray astronomy, cosmic-ray physics, and antimatter studies. We discuss his personal contributions to silicon tracking, calorimetry, data analysis, and his leadership in international collaborations. The conceptual impact of his interdisciplinary approach is examined, and future perspectives in the observation of the high-energy universe are outlined, recognizing that the path forward is built on the foundations he helped lay. Full article

(This article belongs to the Special Issue The Universe Observed With Particle Detectors: Celebrating the Scientific Legacy of Prof. Guido Barbiellini Amidei)

39 pages, 3310 KB

Open AccessReview

MXene-Based Terahertz Metamaterial Biosensors: From Laboratory Simulation to Clinical Application

by Chenxu Jiang, Sitong Li, Junyu Chen, Haoqi Liu, Chenyang Jia, Changlin Yang, Juan Zhang, Jiahao Huang, Xu Xiao and Wenke Xie

Condens. Matter 2026, 11(2), 21; https://doi.org/10.3390/condmat11020021 - 28 May 2026

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Abstract

Terahertz (THz) metamaterial biosensors have emerged as a powerful platform for label-free, non-ionizing biodetection, yet their clinical translation is severely hindered by limited sensitivity, poor anti-interference capability, and a fragmented research chain that rarely extends beyond simulation. Two-dimensional transition metal carbides/nitrides (MXenes) offer [...] Read more.

Terahertz (THz) metamaterial biosensors have emerged as a powerful platform for label-free, non-ionizing biodetection, yet their clinical translation is severely hindered by limited sensitivity, poor anti-interference capability, and a fragmented research chain that rarely extends beyond simulation. Two-dimensional transition metal carbides/nitrides (MXenes) offer a transformative alternative to conventional gold-based metamaterials, providing metal-like high conductivity, abundant surface functional groups for specific biomolecular capture, excellent biocompatibility, and mechanical flexibility. This review systematically examines the recent progress of MXene-based THz metamaterial biosensors, covering structural design strategies, material synergistic system, machine learning-assisted optimization, and performance evaluation metrics. While most studies remain in the simulation stage, a landmark in vivo validation by Yang et al. achieved real-time thrombus monitoring with 94.7% sensitivity and 92.3% specificity, bridging the gap between simulation and clinical application. We identified key bottlenecks hindering clinical translation and propose future directions toward clinically adaptive, full-chain development. This review provides a roadmap for transitioning MXene-based THz biosensors from laboratory simulation to practical point-of-care diagnostics. Full article

(This article belongs to the Special Issue Flexible Matter for Electronics, Photonics, and Energy Conversion)

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32 pages, 738 KB

Open AccessArticle

A Coordination-Based Framework for Superconductivity in Strongly Correlated Systems

by Bin Li

Condens. Matter 2026, 11(2), 20; https://doi.org/10.3390/condmat11020020 - 22 May 2026

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Abstract

High-temperature superconductivity in strongly correlated materials is often accompanied by pseudogap behavior, strange-metal transport, strong phase fluctuations, and reduced superfluid stiffness, particularly in quasi-two-dimensional systems. These features suggest that pairing alone may not determine the onset of global superconductivity. We develop a coordination-based [...] Read more.

High-temperature superconductivity in strongly correlated materials is often accompanied by pseudogap behavior, strange-metal transport, strong phase fluctuations, and reduced superfluid stiffness, particularly in quasi-two-dimensional systems. These features suggest that pairing alone may not determine the onset of global superconductivity. We develop a coordination-based framework in which superconductivity is promoted by the collective organization of internal electronic degrees of freedom coupled to a carrier phase. A minimal lattice model is introduced, combining a U(1) phase sector, an internal coordination field, and an inter-sector coupling. A Landau analysis shows that internal coordination enhances the effective phase stiffness and can destabilize the incoherent state once the coordination amplitude becomes sufficiently large. Monte Carlo simulations of the model confirm that increasing coordination strength enhances phase stiffness and shifts the onset of global coherence to higher temperature. The framework provides a possible organizing interpretation of the separation between pseudogap onset and superconducting coherence, as well as the sensitivity of layered superconductors to reduced dimensionality, competing orders, and vortex-core structure. It is not intended to replace BCS theory, but to extend phase-stiffness-based descriptions to regimes where pairing, local coordination, and global phase coherence are distinct. Full article

(This article belongs to the Section Superconductivity)

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13 pages, 3407 KB

Open AccessArticle

Pseudogap and Condensation in Cuprate Superconductors from NMR Shifts

by Abigail Lee and Jürgen Haase

Condens. Matter 2026, 11(2), 19; https://doi.org/10.3390/condmat11020019 - 16 May 2026

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Abstract

The electronic properties of high-temperature superconducting cuprates are encoded in NMR data. Without microscopic theory, reliable NMR phenomenologies are in demand. Here we make use of the extensive literature data to develop a different understanding of the cuprates from the shifts of the [...] Read more.

The electronic properties of high-temperature superconducting cuprates are encoded in NMR data. Without microscopic theory, reliable NMR phenomenologies are in demand. Here we make use of the extensive literature data to develop a different understanding of the cuprates from the shifts of the

{CuO}_{2}

plane. The Cu shift analysis is based only on the symmetry of the two Cu hyperfine couplings, without assumptions about their size. We use an anisotropic

A_{α}

and isotropic B, as from atomic Cu orbitals, and find two spin components (A- and B-spins) that explain all the shift data. The components differ in size and temperature dependence according to simple rules. Upon doping the cuprates, metallic B-spin appears above a pseudogap temperature, which is shared with the A-spin. Further doping decreases the pseudogap temperature and increases the B-spin, but less so the A-spin. The apparent linear rate of increase in the density of states of the B-spin with doping is nearly threefold above

x = 0.20

, where the pseudogap disappears. The pseudogap temperature is a measure of the coupling between A and B, which suppresses the shifts but not nuclear relaxation. Spin-singlet pairing involves A and B according to three simple condensation rates, which will be discussed. The optimal

T_{c}

demands a special match between A and B. However, the shifts do not simply predict the highest

T_{c}

of all cuprates, in contrast to nuclear relaxation anisotropy and charge sharing between planar Cu and O. Relations to other probes are discussed. Full article

(This article belongs to the Section Superconductivity)

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19 pages, 3296 KB

Open AccessReview

Negative Capacitance Revisited: A Unified Framework Based on Synchronization, Temporal Delay, and Spatial/Quantitative Mismatch

by Yong Sun and Shigeru Kanemitsu

Condens. Matter 2026, 11(2), 18; https://doi.org/10.3390/condmat11020018 - 14 May 2026

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Abstract

Negative capacitance (NC) has been reported across a wide range of physical systems, yet its interpretation has remained fragmented due to the lack of a unified conceptual framework. Existing explanations—spanning ferroelectric free-energy curvature, tunneling transport, plasmonic resonances, and electronic compressibility—have often been treated [...] Read more.

Negative capacitance (NC) has been reported across a wide range of physical systems, yet its interpretation has remained fragmented due to the lack of a unified conceptual framework. Existing explanations—spanning ferroelectric free-energy curvature, tunneling transport, plasmonic resonances, and electronic compressibility—have often been treated as unrelated or even contradictory. This review resolves these inconsistencies by showing that all manifestations of NC arise from non-synchronization between external excitation and internal response. We classify NC into three fundamental categories: temporal mismatch, originating from delays or inertia in charge or polarization dynamics; spatial mismatch, caused by nonuniform field or mode distributions; and quantitative mismatch, resulting from intrinsic parameter reversal such as negative curvature or negative compressibility. Despite their diverse physical origins, these mechanisms share the same mathematical signature (

C_{e f f} = \partial Q / \partial V < 0

). Organizing NC within this unified framework clarifies long-standing ambiguities, connects previously isolated research fields, and establishes a systematic foundation for engineering NC in electronic, photonic, and quantum devices. The framework further highlights tunnel-current-induced NC as a representative single-particle mechanism within the temporal mismatch category, expanding the scope of NC beyond ferroelectricity and collective modes. Overall, this work positions NC not as a singular anomaly but as a universal response class emerging from the interplay between excitation and internal dynamics. Full article

(This article belongs to the Special Issue 10th Anniversary of Condensed Matter: Recent Advances in Condensed Matter Physics)

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21 pages, 798 KB

Open AccessFeature PaperArticle

Impurity-Scattering Assisted Umklapp Scattering as the Origin of Low-Temperature Resistivity in the Normal State of Cuprate Superconductors

by Xingyu Ma, Minghuan Zeng, Huaiming Guo and Shiping Feng

Condens. Matter 2026, 11(2), 17; https://doi.org/10.3390/condmat11020017 - 8 May 2026

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Abstract

The transport experiments reveal that the low-temperature resistivity in the normal state of cuprate superconductors is quadratic in temperature (T-quadratic) in the underdoped pseudogap phase, while it is linear in temperature (T-linear) in the overdoped strange-metal phase; however, the full understanding of these [...] Read more.

The transport experiments reveal that the low-temperature resistivity in the normal state of cuprate superconductors is quadratic in temperature (T-quadratic) in the underdoped pseudogap phase, while it is linear in temperature (T-linear) in the overdoped strange-metal phase; however, the full understanding of these different behaviors is still a challenging issue. Here starting from the microscopic electronic structure of cuprate superconductors, the low-temperature resistivity in the normal state is investigated from the underdoped pseudogap phase to the overdoped strange-metal phase. It is shown that the mechanism requires both the impurity scattering and the umklapp scattering: the impurity scattering is needed to restrict the modification of the distribution function to at and around the antinodal region, while the impurity-scattering assisted umklapp scattering from a spin excitation is at the heart of the behavior in the low-temperature resistivity, where the doping dependence of the temperature scale exists, and presents a similar behavior of the antinodal spin pseudogap crossover temperature. In the low-temperature region above the temperature scale in the overdoped strange-metal phase, the resistivity is T-linear; however, in the low-temperature region below the temperature scale in the underdoped pseudogap phase, the opening of the spin pseudogap lowers the spin excitation density of states at and around the antinodal region, which reduces the strength of the electron umklapp scattering from a spin excitation associated with the antinode, and thus leads to a T-quadratic behavior of the resistivity. Full article

(This article belongs to the Special Issue Superstripes Physics, 4th Edition)

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19 pages, 4072 KB

Open AccessArticle

Josephson Interferometry of Helical Phases in Superconducting Heterostructures

by Paulo J. F. Cavalcanti, Jérôme Cayssol and Alexander I. Buzdin

Condens. Matter 2026, 11(2), 16; https://doi.org/10.3390/condmat11020016 - 29 Apr 2026

Viewed by 637

Abstract

We suggest Josephson interferometry as a quantitative probe of spin–orbit-driven phenomena in superconducting heterostructures. Two distinct mechanisms are analyzed: (i) intrinsic helical superconductivity, producing asymmetric Fraunhofer patterns with lobe deformations and field-reversal asymmetry, and (ii) emergent interfacial magnetism in ferromagnet–superconductor hybrids, where Rashba [...] Read more.

We suggest Josephson interferometry as a quantitative probe of spin–orbit-driven phenomena in superconducting heterostructures. Two distinct mechanisms are analyzed: (i) intrinsic helical superconductivity, producing asymmetric Fraunhofer patterns with lobe deformations and field-reversal asymmetry, and (ii) emergent interfacial magnetism in ferromagnet–superconductor hybrids, where Rashba spin–orbit coupling generates spontaneous fields that rigidly shift the interference fringes. The predicted signatures—flux-shifted interference minima, anisotropic critical current suppression, and angle-dependent pattern distortions—provide direct experimental access to finite-momentum pairing and interface-localized fields via standard Josephson current measurements. Full article

(This article belongs to the Special Issue 10th Anniversary of Condensed Matter: Recent Advances in Condensed Matter Physics)

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11 pages, 1458 KB

Open AccessOpinion

Lasting Aftermaths of the First Incitement for High-Temperature Superconductivity

by Serguei Brazovskii and Natasha Kirova

Condens. Matter 2026, 11(2), 15; https://doi.org/10.3390/condmat11020015 - 27 Apr 2026

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Abstract

Six decades ago, the scientist from Stanford University, W.P. Little, announced a crusade to search for superconductivity, assumed to be heat-resistant in organic materials. Although such an ambitious goal was never realized in practice, this proposal gave rise to the entire ecosystem of [...] Read more.

Six decades ago, the scientist from Stanford University, W.P. Little, announced a crusade to search for superconductivity, assumed to be heat-resistant in organic materials. Although such an ambitious goal was never realized in practice, this proposal gave rise to the entire ecosystem of studies on “synthetic metals,” creating a diverse community of material, experimental, and theoretical activities in low-dimensional electronic systems. We shall briefly review some key steps in this history, examine its main branches, and recall the consequences that remain on the agenda today. Particularly, we shall focus on a phenomenon of electronic ferroelectricity, whose roots can be found in the suggestion of a would-be superconducting polymer. Full article

(This article belongs to the Special Issue Superstripes Physics, 4th Edition)

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10 pages, 1826 KB

Open AccessArticle

Liquid-Precursor-Mediated CVD Synthesis of WSe₂

by Krastyo Buchkov, Peter Rafailov, Nikolay Minev, Vladimira Videva, Ivalina Avramova, Velichka Strijkova, Todor Lukanov, Dimitre Dimitrov and Vera Marinova

Condens. Matter 2026, 11(2), 14; https://doi.org/10.3390/condmat11020014 - 23 Apr 2026

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Abstract

The present study focuses on liquid-precursor-mediated chemical vapor deposition (under ambient pressure and moderate temperature range) of WSe₂ on sapphire using ammonium meta-tungstate and sodium cholate. The investigation provides additional results and information for the WSe₂ cluster formations on sapphire as [...] Read more.

The present study focuses on liquid-precursor-mediated chemical vapor deposition (under ambient pressure and moderate temperature range) of WSe₂ on sapphire using ammonium meta-tungstate and sodium cholate. The investigation provides additional results and information for the WSe₂ cluster formations on sapphire as an extension of our previous study, especially based on structural, chemical and morphological characterization of the observed largest and predominant polygonal WSe₂ domains whose lateral size can reach several hundreds of micrometers. In addition, highly symmetrical shapes were also observed. The Raman spectroscopy and atomic force microscopy identified the formation of both mono- and multilayered WSe₂. Moreover, the Raman spectrum analysis shows a complex peak structure with unusual splitting effects in the second-order modes marking strong activity of excitonic-resonance processes. Full article

(This article belongs to the Section Physics of Materials)

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15 pages, 4625 KB

Open AccessArticle

Magnetic Nanocomposite-Driven Harvesting of Chlorella vulgaris: Enhancing Microalgal Biomass Recovery Using Fe₃O₄ and Fe₃O₄@PEG Nanoparticles

by Lady Johana Endo Aguilar, Indry Milena Saavedra Gaona, Carlos Arturo Parra Vargas, Jahaziel Amaya, Jaime Ernesto Vargas and Daniel Llamosa Pérez

Condens. Matter 2026, 11(2), 13; https://doi.org/10.3390/condmat11020013 - 20 Apr 2026

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Abstract

This study investigates magnetic harvesting of Chlorella vulgaris cultivated under saline and wastewater conditions using Fe₃O₄ and polyethylene-glycol-coated Fe₃O₄ (Fe₃O₄@PEG) nanoparticles synthesized by ultrasound-assisted coprecipitation. TEM showed agglomerated, quasi-spherical particles with mean diameters [...] Read more.

This study investigates magnetic harvesting of Chlorella vulgaris cultivated under saline and wastewater conditions using Fe₃O₄ and polyethylene-glycol-coated Fe₃O₄ (Fe₃O₄@PEG) nanoparticles synthesized by ultrasound-assisted coprecipitation. TEM showed agglomerated, quasi-spherical particles with mean diameters of 13 ± 1 nm (Fe₃O₄) and 15 ± 1 nm (Fe₃O₄@PEG). FTIR confirmed the Fe–O vibrational bands of magnetite and the characteristic PEG vibrations in the coated sample. VSM measurements indicated superparamagnetic behavior, with saturation magnetizations of 72.74 emu/g for Fe₃O₄ and 32.25 emu/g for Fe₃O₄@PEG. SEM–EDX of native and functionalized cells verified nanoparticle attachment on the algal surface. Magnetic separation experiments (OD684) showed a decrease in supernatant absorbance with increasing nanoparticle dose, consistent with biomass removal; the PEG-coated system showed a lower apparent biomass concentration after functionalization. Full article

(This article belongs to the Section Magnetism)

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16 pages, 2287 KB

Open AccessArticle

Phase Transformation and Magnetic Properties of Rapidly Solidified Mn-Al Alloys

by Marco A. Camacho-Peralta, Israel Betancourt and Jose T. Elizalde-Galindo

Condens. Matter 2026, 11(2), 12; https://doi.org/10.3390/condmat11020012 - 17 Apr 2026

Viewed by 583

Abstract

Mn₅₄Al₄₆ alloys with τ-phase as their main component were successfully obtained in a reproducible processing window combining melt-spinning, annealing at intermediate temperatures (450 °C) and low-energy milling. The complete ε → τ phase transformation was driven by thermal decomposition of [...] Read more.

Mn₅₄Al₄₆ alloys with τ-phase as their main component were successfully obtained in a reproducible processing window combining melt-spinning, annealing at intermediate temperatures (450 °C) and low-energy milling. The complete ε → τ phase transformation was driven by thermal decomposition of ε-phase and favored by high grain boundary density inherent to the melt-spun microstructure. An improved magnetic response of the melt-spun Mn₅₄Al₄₆ alloys was observed, as they exhibited saturation magnetization values between 80 and 90 emu/g, together with intrinsic coercivities around 2000 Oe and Curie temperatures between 640 and 648 K. Significant coercivity enhancement over 6000 Oe was predicted, by means of micromagnetic calculations, for alloys with grain size refinement below 100 nm. The efficient, single-step experimental phase transformation with no additional stabilizers for the τ-phase was explained in terms of microstructural features, whereas magnetic enhancement was attributed to lattice distortions promoted by the milling process. This integrated approach introduces a pathway to achieve τ-phase Mn-Al with tunable magnetic performance useful for applications. Full article

(This article belongs to the Section Magnetism)

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17 pages, 5307 KB

Open AccessArticle

Impact of Synthesis Temperature on the Structural, Electronic Structural, Optical, Magnetic, and Electrochemical Properties of SmFeO₃ Nanoparticles

by Sakshi Khandal, Preksha Gagneja, Manas Nasit, Sameer Saharan, Sarita Khaturia, Pratibha Sharma, Sujata Kumari, P. A. Alvi, Naveen Yadav, Bon-Heun Koo, Shalendra Kumar and Kavita Kumari

Condens. Matter 2026, 11(2), 11; https://doi.org/10.3390/condmat11020011 - 31 Mar 2026

Cited by 1 | Viewed by 871

Abstract

The multifunctional attributes of SmFeO₃ make it a promising candidate for the current diverse technological applications. Therefore, in this work, we investigated the effect of synthesis temperature on the magnetic, optical and electrochemical properties of SmFeO₃ nanoparticles at room temperature (SFO-RT) [...] Read more.

The multifunctional attributes of SmFeO₃ make it a promising candidate for the current diverse technological applications. Therefore, in this work, we investigated the effect of synthesis temperature on the magnetic, optical and electrochemical properties of SmFeO₃ nanoparticles at room temperature (SFO-RT) and 50 °C (SFO-50) when prepared through the co-precipitation method. The XRD analysis revealed two distinct phases: SmFeO₃ and Sm₂O₃ as secondary with SmFeO₃ emerging as the primary phase (88–93%). The FESEM images showed the amalgamated morphology of the nanoparticles indicating the enhanced thermal kinetics of the solution which not only limited the particle growth but also facilitated their coalition. The band gap energy was found to be 2.2 and 2.3 eV for SFO-RT and SFO-50, respectively, while the values of saturation magnetization noted were 2.14 and 1.53 emu/g for SFO-RT and SFO-50, respectively. The XPS analysis revealed Sm to be in a +3 oxidation state, while Fe was in a mixed (+3/+2) oxidation state showing an increase in the ionic concentration in SFO-50. From the electrochemical measurements, the highest specific capacitance was observed for SFO-50 (65.8 F/g) as compared to SFO-RT (49.3 F/g). The results indicate a clear effect of synthesis temperature on the properties of SmFeO₃. Here, two factors played a prominent role: one was the morphology, shaped through the particle growth, and the other was the secondary phase. The decrease in the size of the agglomerated particles and phase fraction of the secondary phase brought about necessary changes in the structural attributes to reduce the saturation magnetization and enhance the specific capacitance of SFO-50. Overall, this study shows that the synthesis temperature affects the crystalline structure and phase fractions leading to the modulation of electronic structure, band gap, magnetic interactions and specific capacitance. Full article

(This article belongs to the Special Issue Synergistic Electrochemical and Magnetic Behavior in Nanocomposite Materials)

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Condens. Matter, Volume 11, Issue 2 (June 2026) – 13 articles

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