Synthesis and Characteristics of Multifunctional Magneto-luminescent Nanoparticles by an Ultrasonic Wave-assisted Stӧber Method

Multifunctional magneto-luminescent nanoparticles (NPs) were synthesised by an ultrasonic wave-assisted Stöber method. The multifunctional NPs are composed of magnetic NPs (Fe3O4) and photoluminescent quantum dots (QDs) (ZnS:Mn) in amorphous silica (SiO2) matrix, which was confirmed by X-ray diffraction, Raman scattering spectroscopy, and transmission electron microscopy (TEM). The multifunctional NPs have high saturation magnetisation at room temperature simultaneously with strong photoluminescence (PL) in visible light, which is promising for biomedical applications.

Magnetic Study on Divalent Ion Substituted Barium Hexaferrites

Magnetic properties of Co, Ni and Zn substituted barium hexaferrite (BaM) samples prepared by solid state ceramic method were studied. Saturation magnetisation were found higher for Zn-substituted BaM, whereas, coercivity is higher for Co2+ and Ni2+ ion substituted samples. Anisotropy field for all substituted samples was calculated by the law of approaching saturation. Remanence, squareness and thermomagnetic plot suggest Zn2+ ions restricts the magnetic interaction of various sites in BaM.

Exceptionally high saturation magnetisation in Eu-doped magnetite stabilised by spin–orbit interaction

The significance of the spin–orbit interaction is very well known in compounds containing heavier elements such as the rare-earth Eu ion.

The «nanoscalpel» for microsurgery of glial brain tumours

Glial tumours are among the most common primary brain tumours of neuroectodermal origin characterised by infiltrative growth and widespread invasion of tumour cells into healthy tissue. A highly demanded method for therapy of such tumours may become magnetomechanical microsurgery substituting the scalpel with the «nanoscalpel» consisting of: (1) nanostructures converting the magnetic moment into the mechanical one, and (2) targeted ligands. Suitable structures for the nanoscalpel are magnetic disks with a high degree of saturation magnetisation and absent remanent magnetisation. The search for publications dated 1992-2021 was carried out in the PubMed and e-LIBRARY databases. The search keywords were «magnetic discs», «glial tumors», «microsurgery» and «magnetomechanical transduction». This review discusses biological effects of magnetic disks, their mechanism of action and toxicity. It has been concluded that a «nanoscalpel» remotely controlled using a magnetic field may become an effective and safe tool for microsurgery of glial brain tumours.

Evolution of the Structural and Magnetic Properties of Bulk Fe61Co10B20W1Y8−XPtx Alloys through the Partial Substitution of Pt for Y

This paper presents the results of an investigation into rapidly quenched Fe-based alloys with the chemical formula: Fe61Co10B20W1Y8−xPtx (where x = 3, 4, 5). In these alloys, a small quantity of Pt was added, and the Y content was reduced concurrently. Samples of the aforementioned alloys were injection-cast in the form of plates with the dimensions: 0.5 mm × 10 mm × 10 mm. The resulting structure was examined using X-ray diffractometry (XRD), Mössbauer spectroscopy and scanning electron microscopy (SEM). The results of the structural research reveal that, with a small addition of Pt, areas rich in Pt and Y are created—in which Fe-Pt and Pt-Y compounds, with different crystallographic systems, are formed. It has also been shown that an increase in Pt content, at the expense of Y, contributed to the formation of fewer crystalline phases, i.e., it allowed a material with a more homogeneous structure to be obtained. Magnetic properties of the Fe61Co10B20W1Y8−xPtx (where x = 3, 4, 5) alloy samples were tested using a vibrating sample magnetometer (VSM). The magnetic properties of the investigated materials revealed that the saturation magnetisation increased with increasing Pt content, at the expense of Y. This effect is due to the occurrence of different proportions of crystalline magnetic phases within the volume of each alloy.

Glass formation, nanocrystallisation and magnetic properties of the (Fe1–xCox)79Nb3B18 (x = 0, 0.15, 0.3, 0.45, 0.6, 0.75) metallic glasses

The glass-forming ability (GFA), nanocrystallisation, electrical resistivity and soft magnetic properties of (Fe1-xCox)79Nb3B18 (x = 0, 0.15, 0.3, 0.45, 0.6, 0.75) glassy alloys were investigated. We found that the substitution of Fe by Co is beneficial for improving the GFA. As-spun (Fe0.55Co0.45)79Nb3B18 glassy alloys show the best GFA, along with excellent soft magnetic properties in the supercooled liquid region, with a saturation magnetisation and coercivity of 140 A · m2 · kg-1 and 19.9 A · m-1, respectively, at 60 K. With increasing Co content, the electrical resistivity initially decreases rapidly, and then fluctuates around approximately 70 ± 4 μΩ cm. With increasing the annealing temperature, the saturation magnetisation improves initially, but then decreases for the (Fe0.4Co0.6)79Nb3B18 alloy, and the coercivity does not significantly improve. These newly developed FeCoNbB multicomponent alloys exhibit appreciable GFA, good magnetic properties and low material cost, and they can serve as a promising soft magnetic material for use in industrial applications.

Chemical Synthesis of Rare Earth (La, Gd) Doped Cobalt Ferrite and a Comparative Analysis of Their Magnetic Properties

Lanthanum (La) and gadolinium (Gd) doped cobalt ferrite nanoparticles are synthesized using a soft chemical approach. The analysis of these ferrites using X-ray diffraction (XRD) and transmission electron microscopy (TEM) shows that lattice spacing decreases in the doped ferrite samples. Magnetization data indicates towards the decrease of saturation magnetisation but increase in coercivity with doping. Mössbauer spectroscopy measurements at room temperature indicate increased occupancy of trivalent cations at tetrahedral site. The addition of rare earth dopants reduces the hard-magnetic character of cobalt ferrite.

Alternating current susceptibility and magnetisation of nanocrystalline Co2MnSi Heusler alloy films

The Co2MnSi (CMS) Heusler alloy films with thickness d = 90 ÷ 110 nm were grown by DC magnetron sputtering on both nonheated and heated Si(100) and MgO(100) substrates. The films grown (annealed) at T ≥ 400°C demonstrated a nanocrystalline structure with a partially ordered B2 phase and traces of a highly ordered L21 phase as found from XRD measurements. The films deposited onto the nonheated substrates followed by annealing at Tann = 300 ÷ 500°C demonstrated a gradual increase of the saturation magnetisation, Msat, up to about 4.0 μB/f.u. (at 295 K) while the coercity field, Hc, of the films increased from about 10 to 12 kA/m with Tann increasing from 400 to 500°C. Unusually low Hc values of about 0.1 and 0.3 kA/m have been indicated for the films grown in situ at 400°C on MgO and Si, respectively. A significant increase of the Hc values found for the films grown in situ at Ts = 450°C and reduced Msat values for similar films grown at 500°C have been associated with the instability of the ordered L21 structure at high temperatures.