Co_0.95R_0.05Fe₂O₄ nanoparticles with R = La, Pr, Nd, Sm, and Eu were synthesized via an environmentally friendly sol–gel method. The prepared samples were studied using X-ray diffraction measurements (XRD), transmission electron microscopy (TEM), X-ray photoelectron microscopy (XPS), and magnetic measurements. All compounds were found to be single phases adopting a cubic Fd-3m structure. EDS analysis confirmed the presence of Co, Fe, R, and oxygen in all cases. The XPS measurements reveal that the Co 2p core-level spectra are characteristic for Co³⁺ ions, as indicated by the 2p_3/2 and 2p_1/2 binding energies and spin–orbit splitting values. The analysis of the Fe 2p core-level spectra reveals the presence of both Fe³⁺ and Fe²⁺ ions in the investigated samples. The doped samples exhibit lower saturation magnetizations than the pristine sample. Very good agreement with the saturation magnetization values was obtained if we assumed that the light rare-earth ions occupy octahedral sites and their magnetic moments align parallel to those of the 3d transition metal ions. The ZFC-FC curves indicate that some nanoparticles remain superparamagnetic, while others exhibit ferrimagnetic ordering at room temperature, suggesting the presence of interparticle interactions. The M_r/M_s ratio at room temperature reflects the dominance of magnetostatic interactions.

Co_0.95R_0.05Fe₂O₄ nanoparticles were synthesized using a sol-gel approach incorporating bio-based agents and were found to be single phases adopting a cubic Fd-3m structure. XPS shows the presence of Gd³⁺ and Ho³⁺ ions. The spin–orbit splitting of about 15.4 eV observed in Co 2p core-level spectra is an indication that Co is predominantly present as Co³⁺ state, while the satellite structures located at about 6 eV higher energies than the main lines confirm the existence of divalent Co in Co_0.95R_0.05Fe₂O₄. The positions of the Co 3s and Fe 3s main peaks obtained by curve fitting and the exchange splitting obtained values for Co 3s and Fe 3s levels point to the high Co³⁺/Co²⁺ and Fe³⁺/Fe²⁺ ratios in both samples. The saturation magnetizations are smaller for the doped samples compared to the pristine ones. For theoretical magnetization calculation, we have considered that the heavy rare earths are in octahedral sites and their magnetic moments are aligned antiparallelly with 3d transition magnetic moments. ZFC-FC curves shows that some nanoparticles remain superparamagnetic, while the rest are ferrimagnetic, ordered at room temperature, and showing interparticle interactions. The M_S/Ms ratio at room temperature is below 0.5, indicating the predominance of magnetostatic interactions.

In this research, aluminium-doped biphasic calcium phosphate (Al-BCP) was synthesized by co-precipitation and formulated with hydrolyzed collagen and acetylsalicylic acid (ASA) to yield composites designed as a new class of bone-regenerative biomaterials with enhanced biological performance. Undoped and Al-modified powders (5/10 wt% Al precursor) were prepared at 40 °C (pH ~ 11) and calcined at 700 °C, and composites were produced at a 1:1:0.1 mass ratio (ceramic–collagen–ASA). Structure and chemistry were assessed by X-ray diffraction (XRD), Fourier-transform infrared (FTIR) and Raman spectroscopies, and X-ray photoelectron spectroscopy (XPS). Morphology and elemental distribution were examined by scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX). Biological performance was preliminarily evaluated using HaCaT (immortalized human keratinocytes) viability and antibacterial assays against Staphylococcus aureus and Escherichia coli. XRD confirmed a biphasic hydroxyapatite/β-tricalcium phosphate system and showed that Al incorporation shifted the phase balance toward hydroxyapatite (HAp fraction 54.8% in BCP vs. ~68.6–68.7% in Al-doped samples). FTIR/Raman preserved BCP vibrational signatures and revealed collagen/ASA bands in the composites. XPS/EDX verified the expected composition, including surface N 1s from organics and Al at ~2–5 at% for doped samples, with surface Ca/P ≈ 1.15–1.16. SEM revealed multigranular microstructures with homogeneous Al distribution. All composites were non-cytotoxic (≥70% viability); M_Al10_Col_ASA exceeded 90% viability at 12.5% dilution. Preliminary antibacterial assays against Gram-positive and Gram-negative strains showed modest, time-dependent reductions in CFU relative to controls. These results corroborate the compositional/structural profile and preliminary biological performance of Al-BCP–collagen–ASA composites as multifunctional bone tissue engineering materials that foster a bone-friendly microenvironment, warranting further evaluation for bone regeneration.

This study investigates the electronic, magnetic, and transport properties of the Co_0.5Mn_1.5Al half-Heusler alloy, a promising candidate for spintronic applications due to its potential half-metallic and ferrimagnetic characteristics. Experimental efforts focus on structural characterization using X-ray diffraction to examine substitutional disorder, such as Co/Mn site migration and Mn/Al site mixing, and their impacts on magnetic and transport properties. Magnetic characterization, including magnetization and susceptibility, reveals an N-type ferrimagnetic behaviour with a Curie temperature of 670 K. Transport experiments probe resistance and magnetoresistance across various temperatures and magnetic fields to uncover conduction mechanisms and spin-dependent effects. Theoretical band structure calculations, utilizing the Korringa–Kohn–Rostoker Green’s function method, investigate the electronic structure and the role of disorder in shaping magnetic and transport properties. This integrated experimental and theoretical approach aims to clarify the alloy’s suitability for applications in exchange bias or antiferromagnetic spintronics.

The structural and magnetic properties and band structure results of HoCo_3−xSi_x compounds are reported. First-principles GGA+U+SO calculations, compared with magnetometry experiments, provide deep insight on the magnetic properties of the HoCo₃ compound. They show that HoCo₃ is a robust ferrimagnet, with strongly localized Ho-4f moments in excellent agreement with neutron data and itinerant Co-3d magnetism, where inclusion of the interstitial contribution brings the Co moments into very good agreement with the experimental data. The electronic structure reveals sharp Ho-4f states well below E_F, exchange-split Co-3d bands crossing E_F, and noticeable Ho-5d–Co-3d hybridization that mediates the antiparallel Ho–Co coupling and explains the non-negligible interstitial moment, providing a consistent microscopic picture that supports the experimentally observed increase in magnetization upon Co-Si substitution. Metamagnetic transitions are shown in magnetization isotherms. The observed transitions are broad and can be explained by the distribution of internal magnetic fields which arises from differences in the local environments of cobalt atoms. The magnetic properties were correlated with the theoretical results. Two transitions were revealed below room temperature, one due to a transition to a noncollinear magnetic structure and the other due to a temperature-induced metamagnetic transition.

We demonstrate tunable ferrimagnetic properties in both bulk and thin film ferrimagnetic DyCo₃ compatible with the hosting of topological magnetic chiral textures, namely skyrmions suitable for integration into spintronic applications with classic, neuromorphic and quantum functionalities. The bulk samples were prepared by arc-melting of stoichiometric mixtures under purified argon atmosphere and the thin films by Ultra-High-Vacuum magnetron sputtering from a stoichiometric target. Magnetometry allows us to extract the main magnetic properties of bulk and thin films: the saturation magnetization, the magnetic anisotropy and their variation with temperature. These results are successfully complemented by band structure ab initio DFT calculations. Based on the critical magnetic parameters extracted from experiments, we performed micromagnetic simulations that reveal the skyrmionic potential of our samples in both continuous thin film and nano-patterned architectures.