Synthesis, structural, magnetic property, and Cd(II) adsorption behavior of Ca-substituted MgFe2O4 nanomaterials in aqueous solutions.

In the present study, magnetic nanomaterials (Mg1-xCaxFe2O4, 0.0 ≤ x ≤ 0.8) were prepared via a simple sol-gel method. The samples were characterized using XRD, TEM, SEM, EDX, FTIR, BET, and VSM. The structural and magnetic properties of prepared nanomaterials (NMs) were investigated, and the adsorption capacity of Cd2+ from aqueous solution was evaluated via flame atomic absorption spectroscopy (AAS). The impact of several factors on Cd2+ adsorption such as contact time (1-60 min), pH (3-8), dose (0.003-0.03 g), and initial concentration of Cd2+ (5-60 mg L-1) has been assessed. The adsorption capacity of Cd2+ for the prepared NMs followed the pseudo-second order. Several isotherm models were analyzed, and the Langmuir model was found to be the best fit for NMs. Among as-prepared NMs, Mg0.8Ca0.2Fe2O4 (MCF2, cubic 97%, orthorhombic 3%, qe 100 mg g-1) and Mg0.2Ca0.8Fe2O4 (MCF8, cubic 18%, orthorhombic 83%, qe 90 mg g-1) samples exhibited the highest adsorption performance at conditions, viz., contact time 20 min, pH 7, NM dosage 3 mg, and ions at a concentration 60 mg l-1. Cd removal percentages were achieved 93 and 75 for MCF2 and MCF8, respectively. Overall, the prepared MCF2 and MCF8 NMs could be used as effective adsorbents to eliminate toxic Cd2+ from polluted aqueous solution.

Designing new ferromagnetic double perovskites: the coexistence of polar distortion and half-metallicity.

Advancing technology and growing interdisciplinary fields raise the need for new materials that simultaneously possess several significant physics quantities to meet human demands. In this research, using density functional theory, we aim to design A2MnVO6 (A = Ca, Ba) as new double perovskites and investigate their structural, electronic, and magnetic properties. Structural calculations based on the total energies show the optimized monoclinic and orthorhombic crystal structures for the Ca2MnVO6 (CMVO) and Ba2MVO6 (BMVO) compounds, respectively. Through performing calculations, we reveal that the Jahn-Teller effect plays an important role in polar distortions of VO6 and elongation of MnO6 octahedra, resulting from the V5+(3d0) and Mn3+(3d4:t32ge1g) electron configurations. The spin-polarized calculations predict the half-metallic ferromagnetic ground state for CMVO and BMVO with a total magnetic moment of 4.00 µB f.u.-1 Our findings introduce CMVO and BMVO double perovskites as promising candidates for designing ferromagnetic polar half-metals and spintronic applications.

Density functional study of structural, electronic and magnetic properties of new half-metallic ferromagnetic double perovskite Sr2MnVO6.

In this paper, a new half-metallic (HM) double perovskite compound is predicted with the simultaneous presence of ferromagnetism and polar distortion. The structural, electronic and magnetic properties of Sr2MnVO6 (SMVO) are calculated by density functional theory (DFT) with both generalized gradient approximation (GGA) and GGA + U approaches, where U is the on-site Coulomb interaction parameter. Different orderings of B (B') cationic sites in A2BB'O6 double perovskite structure are evaluated, including rocksalt, columnar and layered arrangements for cubic, monoclinic and tetragonal crystal structures. It is found that the most stable ordering is obtained when B and B' are placed in a layered type ordering for a tetragonal crystal structure with I4/m space group, which is confirmed by phonon calculations. The B-site ordering of the Mn3+ and V5+ ions in a layered configuration leads to ferromagnetically coupled magnetic moments of 4.17 µ B at Mn site and 0.23 µ B at V site. Finally, SMVO is found to be a half-metallic ferromagnetic (HM-FM) compound with a band gap of 0.65 eV in a spin down channel with off-centered displacement of V atoms in the octahedral cage (second order Jahn -Teller effect) which can cause ferroelectricity. Therefore, SMVO is predicted to be a polar HM material and a promising candidate for multiferroic property with potential application in spintronics.