Magnetic-field-driven Lifshitz transitions are typically considered zero-temperature phenomena involving Fermi-surface reconstruction without symmetry breaking. Here, we report an unconventional Lifshitz transition in TaCo2Te2 that emerges exclusively within a narrow finite-temperature window under cooperative tuning by both temperature and magnetic field. Bulk-sensitive transport and thermoelectric measurements demonstrate continuous Fermi-surface renormalization at low temperatures, where the transition is sharply triggered by a critical magnetic field. Crucially, neutron diffraction reveals the absence of structural or magnetic phase transitions, while angle-resolved photoemission spectroscopy shows no spectral anomalies in electronic structure without magnetic field. These observations constrain the mechanism to a Zeeman-driven process invisible to equilibrium probes, establishing a paradigm where Fermi-surface topology is jointly controlled by temperature and magnetic field.

Nanotechnology is revolutionizing various fields, including environmental monitoring. CuO nanorods (NRs) based gas sensors exhibit high sensitivity and selectivity for precise NO₂ detection, crucial for addressing environmental and health risks. This study explores the impact of reaction temperature and pH on the structural, optical, and electronic properties of CuO NRs synthesized by co-precipitation. Rietveld refinement of X-ray diffraction (XRD) data confirmed the formation of single-phase monoclinic CuO NRs (space group: C2/c), while transmission electron microscopy (TEM) analysis verified their nanorod morphology. FESEM analysis with size distribution revealed average diameters of nanorods 143 nm for CuO NRs-1 and 75 nm for CuO NRs-2. UV–Vis spectroscopy was employed to analyze the optical properties of the synthesized nanoparticles. Linear and nonlinear optical properties were analyzed to understand the material’s optical behavior. Dispersion parameters and high-frequency dielectric constant (ε∞) were calculated using the Wemple-DiDomenico model, and both volume (VELF) and surface (SELF) energy loss functions were subsequently analyzed. The computed plasma frequencies (ωp) for CuO NRs-1 and CuO NRs-2 are 3.28 × 1015 Hz and 2.08 × 1015 Hz, respectively, while their electronic polarizations (αp) are 2.73 × 10–24 cm3 and 2.66 × 10–24 cm3. Nonlinear optical parameters, including refractive index and third-order susceptibility, were evaluated. Furthermore, the CuO NRs-2 sensor exhibited the highest sensing response toward 1–10 ppm of NO2 gas, significantly outperforming its responses to SO2, CO, H2, and NH3. The enhanced selectivity and sensitivity at the optimized operating temperature of 200 °C are attributed to the CuO/Cu2O heterostructure present in CuO NRs-2.

The evolution of the structural, magnetic and transport properties of the intermediate compounds Nd 2-x SrxCoIrO6 with x = 0.2, 0.4, 0.6, 1 and 1.5 have been studied to establish important roles of sizes and oxidation states of cations on various phases. The replacement of Nd3+ by Sr2+ primarily influences the oxidation states of Co (Co2+ -> Co3+) and Ir (Ir4+ -> Ir5+) ions to maintain the charge neutrality in the entire system. The Sr dopants give rise to an increasing Co/Ir antisite disorder (ASD) to accommodate the variation of charge state and ionic radius of Co and Ir. The nature of magnetic interaction induced by Sr changes from being a ferrimagnetic (FIM) to a more dominant antiferromagnetic. The suppression of the second magnetic transition below 30 K in samples for x > 0.2 is entirely due to dilution of the Nd-Nd magnetic interaction. The combined effects of ASD and mixed oxidation state of Co and Ir ions generate various types of magnetic exchange pathways and create competitive magnetic interactions to stabilize a particular magnetic ground state. In the middle compound NdSrCoIrO6, a Griffith like phase in the temperature region 65-150 K and exchange bias field of 658 Oe at 2.3 K under a cooling field of 50 kOe has been observed. The compounds show an insulating kind of behaviour, and with hole doping the value of room temperature resistivity drastically decreases. The nature of conduction is found to follow three dimensional Mott's variable range hopping process.

We report herein an unusual occurrence of solvent-induced di- and hexanuclear lanthanide (Ln 2 and Ln 6 ) complexes using an unorthodox N-rich pyridyl-pyrazole-based ligand. The crystal structures of Ln 2 and Ln 6 complexes are isostructural and show a common feature: a nonpolar periphery and a polar core where the paramagnetic lanthanide centers are exclusively bridged by oxygen atoms. Such favorable magnetic exchange coupling leads to interesting magnetic behaviors with befitting single-molecule magnet (SMM) and magnetocaloric effect (MCE) features. The Dy 2 complex exhibits SMM behavior with befitting frequency and temperature-dependent out-of-phase signals along with an U eff value of similar to 49.3 K and a relaxation time of 4.82 x 10-9 s. Both Gd 2 and Gd 6 complexes exhibit cryogenic magnetic cooling with a -Delta S M value of 15.2 and 40.6 J kg-1 K-1, respectively, under an applied magnetic field of 5 T at 4 K and 8 T at 2.3 K. Detail theoretical investigations were also performed, which demonstrate gratifying synergism between theoretically derived and the experimentally obtained magnetic properties. The ionic conductivity measurements show excellent ionic conductivity values in the range of 4.32 x 10-4 to 7.92 x 10-4 S/cm at 80 degrees C and 95% relative humidity.

The application of an external magnetic field to the cathode shows great promise in facilitating the hydrogen evolution reaction (HER) via water electrolysis. However, the criteria for designing such cathodes are still under investigation. Among various aspects, understanding the effect of different magnetic states of the cathode material is crucial, especially for the HER in alkaline conditions, which possesses different reaction steps compared to that in acidic conditions. Herein, we present MnSe2 as a cathode material for the magneto-electrocatalytic HER in alkaline media, utilizing its dimension-dependent magnetic phase transition. By tailoring its dimensionality, we have achieved room-temperature ferromagnetism in its quasi-two-dimensional (2D) form, whereas its bulk counterpart exhibits paramagnetism. Upon being subjected to a low external magnetic field of 0.4 T at -182 mV (vs RHE) overpotential, quasi-2D MnSe2 exhibited a 120% improvement in current density compared to itself at zero magnetic field, while negligible changes were observed in the bulk material. This performance enhancement under a magnetic field could originate from the higher spin polarization of the ferromagnetic catalyst. This work signifies a conceptual advancement of the catalyst's spin state in magnetically enhanced electrocatalytic reaction kinetics.

Self-assembling nanorods like copper oxide (CuO) nanoparticles (NPs) have been successfully synthesized using two different copper cationic precursors to investigate their structural, optical, and magnetic properties. These NPs are employed in anticancer applications. Both the CuO-NPs have been tested for their toxicity on human cells. The XRD patterns confirm the formation of monoclinic crystal structures for both the systems. The FESEM microstructural surface morphology shows high agglomeration and a typical elemental composition is evaluated from EDAX analysis. The HRTEM analysis reveals high crystalline CuO nanorods with diameters in the range of 60 similar to 94 nm and 09 similar to 22 similar to 22 nm for two different nanoparticles named CuO-NPs1 and CuO-NPs2, respectively. The optical band gap of CuO-NPs has been calculated from UV-visible absorption spectra and is found to be 2.18 eV and 2.55 eV for CuO-NPs1 and CuO-NPs2, respectively. FTIR analysis provides insights into the chemical compositions of both the CuO-NPs. Magnetization study using vibrating sample magnetometer (VSM) indicates antiferromagnetic-like properties associated with weak ferromagnetic behaviour. Cytotoxicity tests on MCF-7 cell lines show that CuO-NPs2 exhibit more pronounced effect with IC50 50 of 22.95 mu g/mL. The toxicity of both the CuO-NPs are also assessed using human lymphocytes, suggesting that CuO-NPs could be promoted as anticancer agents while remaining non-toxic to biological systems.

In the global development of alternative and sustainable fuels, H-2 has gained prime research interest as combustion of it results in energy with zero carbon footprint. In this context, non-noble metal-based double perovskite oxides with their wide tunable structure gained interest from researchers as an effective electrocatalyst for water oxidation in alkaline medium. However, their low catalytic efficacy and durability limit their application for the industrial scale. Here, we present several Fe-Co-based double perovskite oxides tuning their A-site with lanthanides for overall water splitting and hybrid electrolysis for energy-saving H-2 production. The best Fe-Co-based double perovskite oxide, Eu2FeCoO6, demonstrates very high trifunctional electrocatalytic activity for oxygen evolution reaction (OER) and small alcohol molecule oxidation, along with hydrogen evolution reaction (HER). Overpotentials (eta(10)) of 220 mV for the OER and 238 mV for the HER were attained at 10 mA cm(-2) current density in 1 M NaOH (pH = 14). Also, Faradaic yields of 85 and 89% were achieved for ethanol oxidation (EtOR) and benzyl alcohol oxidation (BnOR), respectively, with the best catalyst. Moreover, in a two-electrode electrolyzer with 0.1 M benzyl alcohol (as an electrolyte) and Eu2FeCoO6 as a bifunctional catalyst (both as the cathode and anode, Eu2FeCoO6 (-)parallel to Eu2FeCoO6 (+)), a cell potential of 1.75 V was enough for oxygenation of benzyl alcohol along with the production of H-2. A 150 mV advantage in cell potential was gained in BnOR-aided H-2 generation compared with overall water oxidation.

For the industrial-scale production of hydrogen via water electrolysis, water splitting in acidic conditions is in forefront compared to that in alkaline medium. However, the lack of earth-abundant, cost-effective, highly active, and durable anode electrocatalysts has impeded industrial scaling. Owing to the exceptional activity and stability in an acidic medium, Ir based multimetal perovskite oxides have evolved as prime candidates for the acidic oxygen evolution reaction (OER). Excluding very low Ir loading, Ir based double perovskite oxides also provide abundant structural and compositional flexibility, so maximization of activity and stability could be grasped by tuning the A-site and B-site ions in A(2)BIrO(6). Changing the ionic radii and oxidation state of the A-site cation has a crucial impact on determining the electrocatalytic OER activity of these perovskites. Herein, we synthesized variable lanthanide based double perovskites, viz., Pr2CoIrO6, Nd2CoIrO6, Sm2CoIrO6, and nonlanthanide Sr2CoIrO6. Nd2CoIrO6 showed the best OER activity and needs only 234 mV overpotential (eta) to acquire a current density of 10 mA cm(-2) with a mass activity of 0.69 A/mg(Ir) (eta = 300 mV) and excellent catalytic stability of 48 h. Density functional theory (DFT) calculations reveal that the d-band center of Nd2CoIrO6 perovskite is in close proximity to the Fermi level, underscoring its increased potential for the OER in agreement with experimental findings. Notably, valence and conduction band edges are primarily influenced by the O(p) and Ir(d) orbitals, with a minor contribution from the Co(d) states. The overall performance of Nd2CoIrO6 outperforms that of benchmark IrO2 and most of the state-of-the-art catalysts reported so far. Nd2CoIrO6 was further explored for isopropyl alcohol oxidation. Excellent selectivity and faradaic yield for acetone was observed. Particularly in acidic isopropanol solution, a potential advantage of 210 mV at 10 mA cm(-2) (compared to OER) was found to oxidize isopropanol into value-added chemicals, viz., acetone, along with the generation of hydrogen.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

We report herein two multifunctional metal- organic frameworks (MOFs) that exhibit excellent mutually inclusive electrical and magnetic properties. Accordingly, two cobalt and nickel based MOFs (Co-MOF, Ni-MOF) were generated using a flexible bispyrazole based ligand and 2-sulphono terephthalic acid. The idea is to generate paramagnetic metal ion based magnetic MOFs, which can also be used to fabricate electrical devices by utilizing the immobilized free sulfonic groups and encapsulated H-bonded water clusters for active charge species generation and transportation. Further support comes from the intriguing structural features of the MOFs that include extensive H bonded water clusters, free sulfonic acid moiety, or syn-anti bridged carboxylates, which make them highly suitable candidates for generating electrical and magnetic materials. Further complementary support for their candidature comes from the high thermal, chemical, and physical stability of the MOFs. The impedance spectroscopy data and I-V results unequivocally support the suitability of the MOFs for electronic device fabrication showing a befitting conductivity value of 1.80 x 10-4 S/m with an ideality factor of 1.06 for Ni-MOF. Interestingly, the Co-MOF shows a light dependent behavior with conductivity values of 9.09 x 10-5 S/m (dark) and 6.31 x 10-4 S/m (light) and ideality factors of 0.78 (dark) and 0.92 (light). The MOFs, fitted with a free sulfonic acid moiety and extensive H-bonded water clusters, show high potential for proton exchange membrane fuel cells (PEMFCs) development with corroborating proton conductivity values of 1.95x 10-3 S/cm and 5.80 x 10-4 S/cm for Ni-MOF and Co-MOF, respectively, at 95% relative humidity and 85 degrees C. Moreover, the interesting structural aspects like syn-anti bridged carboxylates prompt us to explore the magnetic behavior of the MOFs. The NiMOF shows some interesting antiferromagnetic behavior. The Co-MOF reveals intriguing single molecule magnet behavior with a Ueff value of 34 K and moderate relaxation time of 3.5x 10-8 s.

We report rich magnetic behavior for Co-Ir based double perovskites consisting of different rare earth cations Pr and Nd: Pr2CoIrO6(PCIO) and Nd2CoIrO6(NCIO). Both oxides show an antisite disorder of 10% and a ferrimagnetic transition,TFiMaround 96 K and 98 K respectively. The long range magnetic ordering is arising from the canted antiferromagnetic ordering between the Co2+and Ir4+ions. A prominent peak around 27 K in magnetization data of NCIO indicates that the total moment of Nd ion is antiferromagnetically coupled to the Co-Ir sublattice. The long range order of the Nd sublattice is corroborated by the evidence of an anomaly in specific heat at very low temperature. The compounds exhibit a maximum change of magnetic entropy of 0.57 (0.48) J kg.K-1atTFiMin a magnetic field of 5 T. The strong spin-orbit coupling in 5dstates of Ir and cation disorder lead to the Mott insulating phase as found from the analysis of temperature dependent resistivity. These unique behaviors suggest an interesting interplay between localized Pr/Nd-4f, itinerant Co-3dand Ir-5delectrons.

The low temperature vibrational properties of Ir-based double perovskite Sm2CoIrO6 (SMCO) has been investigated by Raman scattering to gain an insight into the mechanism of the isostructural phase transition present at -104 K under ambient atmospheric pressure. The temperature dependent Raman study also reveals the development of short range magnetic correlation above the long range magnetic ordering. From the comprehensive temperature dependent study, it is found that the system before entering the state of long range ferrimagnetic ordering, undergoes from a state of conventional paramagantism to a state of correlated paramagnetism. The interaction of the phonons with the underlying magnetic degrees of freedom has been studied for the most prominent mode in terms of Fano asymmetric parameter. The strong spin-phonon coupling below the global ordering temperature results in a significant softening of the phonon modes involving stretching and/or vibration of the (Co/Ir)O-6 octahedra.

Magnetic insulators or semiconductors having high dielectric constant are a class of materials which are very promising from experimental perspective and thus have been extensively investigated herein. The multiple magnetic phases, observation of conventional exchange bias phenomenon and high dielectric constant in La2Cu0.9Mn0.1IrO6 double perovskite is reported. The incorporation of Mn (10%) into predominantly antiferromagnetic spin structure of La2CuIrO6 leads to mixed valence state of Mn (Mn2+ and Mn3+). We report here the observation of conventional exchange bias phenomenon and high dielectric constant in La2Cu0.9Mn0.1IrO6 double perovskite. The compound crystallizes in triclinic structure with P 1 space group and undergoes two magnetic transitions at Neel temperature TN = 66 K and Curie temperature TC = 14 K respectively. Large value of conventional exchange bias (CEB) of 731 Oe for a bias cooling field of 50 kOe at T = 3 K is the major highlight. Analysis of the cooling field dependence on the exchange bias field and magnetization indicates the pinned or frozen ferromagnetic (FM) spins give rise to the unidirectional shift of the hysteresis loops known as the EB effect. The training effect has been interpreted using spin frozen and spin flipping model. Dielectric constant reveals a step like increase from low temperature (T < 90 K) value of -45 to colossal value of -5350 at high temperature (T-280 K).

The effect of partial electron doping (10% Fe) in the antiferromagnetic (AFM) double perovskite La2CuIrO6 (LCO) has been investigated at the macroscopic level using X-ray diffraction (XRD), and DC Magnetic measurements to study the evolution of complex magnetic order. The experimental observations indicate a significant modification in the nature of microscopic magnetic interaction induced by charge imbalance resulting in strong ferromagnetic (FM) ordering in the parent antiferromagnetic LCO. The nature of magnetic interaction results in a cluster-glass state (CG) with novel zero-field-cooled exchange bias (ZEB) and conventional exchange bias (CEB) effect at low temperature. Obtained ZEB field value is 0.735 kOe at 3 K, while an unusually large CEB field of 9.24 kOe for a bias cooling field (H-B) of 50 kOe has been observed at the same temperature. The doped LCO also shows the training effect in field cooled M(H) measurements, following the frozen spin relaxation behavior, indicating the cluster-glass (CG) nestle in the interface/pinning boundary. The emerged complex exchange interaction among different magnetic ordering, i.e., FM, AFM, and CG, significantly influences the CEB as well as ZEB.

In this paper we have explored and analyzed the crystal structure, magnetic and optical properties of Ru doped double perovskite compound Ba2CuTe1-xRuxO6 (x = 0, 0.05 and 0.1). Detailed analysis of powder x-ray diffraction data at room temperature confirms the formation of single phase with monoclinic crystal structure (space group C2/m). A careful deconvolution of Ru and Cu x-ray photoelectron spectra indicates the formation of mixed oxidation states: Ru (4+ and 5+) and Cu (2+ and 3+). Electron paramagnetic resonance (EPR) spectra also support the presence of EPR silent Cu3+ (S = 0) ions. A broad overturn around 66 K in temperature dependent magnetization data of pure compound gets gradually suppressed in Ru doped samples. Magnetic frustration decreases with increase of Ru doping concentration due to different magnetic competitive interactions. Optical properties (change of color) are influenced due to the formation of 4d (Ru) energy levels in the vicinity of Fermi level.

Iridium-based double perovskites having mixed 3d–5d–4f magnetic sub-lattices are expected to exhibit exotic magnetic phenomenon. In this paper, we report a study of structural, magnetic and transport properties of the mixed 3d–5d–4f double perovskite Sm2CoIrO6 (SMCO), which crystallizes in monoclinic structure with space group P21/n and the crystal symmetry remains same throughout the measured temperature down to 15 K. High resolution synchrotron x-ray diffraction reveals an isostructural phase transition around 104 K. Magnetization measurements on polycrystalline samples indicate that SMCO orders ferrimagnetically at T FiM = 104 K; while, a second transition is observed below 10 K due to the rare-earth (Sm3+) ordering. The ferrimagnetic transition is well-understood by Néel's two-sublattice model, which is primarily ascribed to antiferromagnetic coupling between Co2+ and Ir4+ sub-lattices. Electronic transport measurement shows the insulting behaviour of SMCO, which follows Mott variable-range hopping conduction mechanism. However, dielectric measurements as a function of temperature rules out the presence of magneto dielectric coupling in this compound.

Polycrystalline Nd2CoIrO6 double perovskite crystallizes in monoclinic crystal structure with P21/n space group. The average grain size of powder sample is 400-500 nm. The dielectric, impedance and ac conductivity of the sample were studied in the temperature range 5-300 K and in the frequency range 20 Hz-2 MHz. Dielectric constant reveals a step like increase from low temperature value of ∼5 to colossal value of ∼104 at high temperature. High value of dielectric constant is associated with Maxwell-Wagner polarization due to large grain boundary capacitance. Cations (Co2+ and Ir4+) disorder leads to variable range hopping conduction of electrons in grain and grain boundary regions. Distribution of grain size induces distribution of relaxation time as confirmed from depressed semicircles in Nyquist plots. Frequency dependent conductivity follows universal power law behavior.

CaCu3Ru4O12 is a Pauli paramagnetic metal oxide consisting of both 3d and 4d magnetic ions in a Cubic-perovskite crystal structure. This present work probes a change in magnetic ground state with the influence of Co. Polycrystalline CaCu3Ru4-xCoxO12 (0 <= x <= 0.1) powder samples have been prepared by conventional solid state reaction under ambient condition. X-ray photoelectron spectroscopy suggests the formation of Cu3+ and Co3+ ions. The absence of electron paramagnetic resonance (EPR) signal for x = 0.1 also confirms the presence of low spin Cu3+ in doped system. Partial replacement of Ru4+ by Co3+ leads to a transition from itinerant Pauli to localized paramagnetism. Resistivity follows Fermi liquid behavior at low temperature.