The development of lanthanide-based molecular magnetic materials incorporating organic radicals requires a fundamental understanding of how ligand modification influences magnetic exchange interactions while preserving the coordination environment around the metal center. In this predictive computational study, the electronic structures and magnetic properties of two hypothetical Gd3+ complexes with donor–acceptor semiquinone–nitronylnitroxide biradicals, Tp2Gd(SQNN) (1) and Tp2Gd(SQPhNN) (2), were investigated using ab initio calculations and compared with the previously characterized monoradical complex Tp2Gd(SQ); Tp is hydro-tris(1-pyrazolyl)borate. For the first time, the related zinc complex TpCumZn(SQNN) (3) was also computed using its experimental geometry, providing a reference point for the reliability of the computational protocol. The inclusion of dynamic correlation at the NEVPT2 (N-Electron Valence State Perturbation Theory, 2nd order) level was essential for correctly predicting the antiferromagnetic nature of the Gd3+–biradical interaction, while the SA-CASSCF (State-Average Complete Active Space Self-Consistent Field) alone yielded a ferromagnetic ground state. The computed exchange interaction in the –2J formalism between Gd3+ and the biradical in complexes 1 and 2 (J ≈ –2.1 cm−1) is more than two times weaker than that in Tp2Gd(SQ) (J = –5.4 cm−1). The intraligand exchange parameters JSQ–NN = 690 cm−1 and JSQ–PhNN = 122 cm−1 reflect strong ferromagnetic coupling within the biradical moieties. Application of the valence bond configuration interaction model yielded electronic coupling matrix elements HDA of 15,283 cm−1 and 6546 cm−1 for the yttrium analogues of 1 and 2, respectively. The calculated magnetic susceptibility data for complexes 1 and 2 closely resemble the behavior of Tp2Gd(SQ), although the characteristic temperatures differ due to the unequal exchange coupling strengths. This study demonstrates that modern computational methods enable consistent prediction of the key magnetic characteristics of heterospin systems based on their possible molecular structures.
Neodymium-based permanent magnets (Nd2Fe14B) are widely applied in technologies such as electric vehicles and wind turbines due to their high magnetic strength and resistance to demagnetization. Despite these advantages, their performance is limited by a low operating temperature (<585 K) and poor mechanical properties. This study explores the influence of rare earth substitutions, specifically Gd and Ce, on the structural, electronic, mechanical, and magnetic behaviour of Nd2Fe14B using ab initio density functional theory. Thermodynamic stability, assessed via heats of formation, indicates NdCeFe14B as the most stable composition. Partial substitution with Gd enhances ductility, mechanical stability, magnetic strength, and Curie temperature, offering a pathway to improved permanent magnets. These insights support the design of advanced magnetic materials with higher operating temperatures and superior mechanical performance.
Herein, high-entropy ferrites (HEFs) represent a transformative frontier in solid-state chemistry and materials physics, shifting design paradigms from conventional mono- or co-substituted ceramics toward multi-component, single-phase solid solutions. Stabilized by a massive configurational entropy (ΔSconf > 1.5 R), these systems incorporate five or more principal cations into a single crystalline matrix, such as cubic spinel (Fd3¯m), perovskite, or hexagonal structures. This comprehensive review systematically evaluates recent breakthroughs in HEF design, tracing the continuous lineage from advanced synthesis methodologies, including modified Pechini sol–gel and hydrothermal routes, to local coordination environments and macroscopic functional expressions. We detail how intense local lattice distortions and polyhedral buckling alter metal–oxygen ligand bond parameters, disrupting traditional collinear A-O-B superexchange pathways to induce quantum magnetic frustration, low-temperature spin-glass behavior, and spontaneous exchange bias effects. Beyond fundamental physics, this work highlights the multi-cation “cocktail effect” across cutting-edge applications, emphasizing its role in high-frequency electromagnetic interference (EMI) shielding, multi-redox heterogeneous catalysis, and high-capacity electrochemical energy storage. Finally, we address current computational bottlenecks in Density Functional Theory (DFT+U) simulations and propose a roadmap for accelerating phase stability predictions and magnetic footprint tuning through the integration of high-throughput workflows and closed-loop, data-driven machine learning architectures. By bridging the gap between thermodynamic theory and targeted application, this review provides a foundational framework for the next generation of entropy-stabilized functional devices.
The journal retracts the article titled “Structural and Photocatalytic Studies on Oxygen Hyperstoichiometric Titanium-Substituted Strontium Ferrite Nanoparticles” [...]
Efficient water disinfection remains a critical challenge due to the persistence of waterborne pathogens. This study reports the synthesis and characterization of magnetically recoverable Fe3O4-Cu composite nanoparticles designed for efficient water disinfection. The particles consist of magnetite nanoparticles functionalized with metallic copper (Cu0) nanoparticles. The nanoparticles were synthesized via oxidative coprecipitation and characterized using x-ray diffraction, Mössbauer spectroscopy, DC magnetometry and transmission electron microscopy (TEM). Antibacterial assay was conducted against Staphylococcus aureus and Escherichia coli. Rietveld refinements confirmed lattice parameters and crystallite sizes of 8.40 Å (102 nm) for Fe3O4 and 3.62 Å (101 nm) for Cu. The 57Fe Mössbauer spectrum for Fe3O4, at 300 K, exhibited two sextets with isomer shifts and hyperfine magnetic fields of 0.61 mm/s (45.3 T) and 0.34 mm/s (48.9 T), corresponding to Fe2.5+ at octahedral sites and Fe3+ at tetrahedral sites, respectively. The isothermal magnetization at 300 K for Fe3O4 showed hysteretic behavior with saturation magnetization of 80.2 emu/g, remanence of 17.9 emu/g and coercivity of 197 Oe. Antibacterial efficacy was evaluated against Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative) using both the poisoned food method and batch removal assays. Results demonstrated a significant strain-dependent sensitivity; Fe3O4-Cu NPs inhibited S. aureus growth at concentrations as low as 0.1 mg/mL while E. coli required 0.5 mg/mL for similar effects. In batch experiments, 0.5 mg/mL of NPs achieved 100% bacterial removal for S. aureus, whereas 0.75 mg/mL was necessary for E. coli. Furthermore, the magnetic core facilitated rapid separation and reusability; the NPs maintained high efficiency against both strains in a second cycle, showing no significant loss of antibacterial activity. These findings highlight the potential of Fe3O4-Cu nanocomposites as high-performance, reusable biocides for targeted water treatment applications.
