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Zinc-doped yttrium orthoferrite nanocrystals having the perovskite structure were prepared by coprecipitation of yttrium, zinc, and iron hydroxides. The limiting zinc doping level of the yttrium ferrite to yield a ZnFe2O4 spinel second phase was determined. The yttrium orthoferrite particle size was found to be a nonmonotone function of dopant concentration. The specific magnetization of yttrium ferrite nanocrystals increases with increasing zinc doping level from 0.242 A m2/kg (in undoped YFeO3) to 1.327 A m2/kg (the ratio (1–x)YFeO3: xZn (x = 0.4)) at Т = 300 K in 1250-kA/m field. A zinc ferrite impurity in samples enhances the ferromagnetism of the material.

Nanopowders La1–x Zn x FeO3 (nominal degree of doping x nom = 0, 0.05, 0.075, 0.1, 0.15, 0.2, 0.3, and 0.4) were synthesized by the sol–gel method using aqueous ammonia as a precipitator and were then annealed at 950°C for 60 min. From the data of X-ray powder diffraction analysis and local electron probe microanalysis, the maximum actual limit of doping of lanthanum ferrite with zinc was determined: x = 0.072. The dependence of the particle size on the Zn2+ content was found to be nonmonotonic. The magnetic characteristics (specific magnetization J, coercivity H c, and magnetic susceptibility χ) of samples at temperatures of 300 and 100 K in fields of up to 1300 kA/m. It was shown that, with increasing degree of doping, J increases from 0.188 A m2/kg (at x = 0) to 0.245 A m2/kg (at x = 0.072), and χ varies nonmonotonically from 11.5 × 10–6 (at x = 0) to 15.3 × 10–6 (at x = 0.072) (at 300 K). With decreasing measurement temperature to 100 K, the magnetization and susceptibility monotonically increase.

The research and development for biomedical applications are recently focused on multifunctional nanoparticles. To integrate various functionalities, different methods of modifying the particle’s physical properties are developed. Among the considered, nanodiamond (ND) is a promising candidate for the development of multifunctional complex due to its variable features in size, structure, surface chemistry, physical properties, and biocompatibility. In addition to its well-studied structural, surface, electrochemical and photonic properties, strong magnetism of ND can be observed. In the present work, magnetically modified ND is introduced in terms of its bioapplications. Along with the soft ferromagnetism of ND, the increased fluorescence at one- and two-photon excitation is realized. Utilizing the combined magnetic and fluorescence properties of the magnetically modified ND, fluorescence imaging, fluorescence lifetime imaging and manipulation of cells by magnetic field are demonstrated. The perspectives to use the magnetic ND for drug delivery, cells magnetic separation and filtration, in bioengineering to control the cell distribution combined with imaging and treatment are discussed.