Rare earth metals (REM) occupy a special and important place in our lives. This became especially noticeable during the rapid development of industry in the industrial era of the twentieth century. The tendency of development of the rare-earth metals market certainly remains in the XXI century. According to experts estimates the industry demand for chemical compounds based on them will tend to grow during the nearest years until it reaches the market balance. At the same time, the practical use of high-purity rare-earth metals requires the most accurate understanding of the physical properties of metals, especially magnetic ones. Despite a certain decline in interest in the study of high-purity REM single crystals during the last decade, a number of scientific groups (Ames Lab, Lomonosov Moscow State University (MSU), Baikov Institute of Metallurgy and Materials Science Russian Academy of Science (RAS)) are still conducting high-purity studies on high-purity metal samples. The present article is a combination of a review work covering the analysis of the main works devoted to the study of heavy REMs from gadolinium to thulium, as well as original results obtained at MSU. The paper considers the electronic properties of metals in terms of calculating the density of states, analyzes the regularities of the magnetic phase diagrams of metals, gives the original dependences of the Neel temperature and tricritical temperatures for Gd, Tb, Dy, Er, Ho, Tm, and also introduces a phenomenological parameter that would serve as an indicator of the phase transformation in heavy REMs.

Hybrid multimodal nanoparticles, applicable simultaneously to the noninvasive imaging and therapeutic treatment, are highly demanded for clinical use. Here, Fe-Au core-satellite nanoparticles prepared by the method of pulsed laser ablation in liquids were evaluated as dual magnetic resonance imaging (MRI) and computed tomography (CT) contrast agents and as sensitizers for laser-induced hyperthermia of cancer cells. The biocompatibility of Fe-Au nanoparticles was improved by coating with polyacrylic acid, which provided excellent colloidal stability of nanoparticles with highly negative ζ-potential in water (−38 ± 7 mV) and retained hydrodynamic size (88 ± 20 nm) in a physiological environment. The ferromagnetic iron cores offered great contrast in MRI images with r₂ = 11.8 ± 0.8 mM⁻¹ s⁻¹ (at 1 T), while Au satellites showed X-ray attenuation in CT. The intravenous injection of nanoparticles enabled clear tumor border visualization in mice. Plasmonic peak in the Fe-Au hybrids had a tail in the near-infrared region (NIR), allowing them to cause hyperthermia under 808 nm laser exposure. Under NIR irradiation Fe-Au particles provided 24.1 °C/W heating and an IC₅₀ value below 32 µg/mL for three different cancer cell lines. Taken together, these results show that laser synthesized Fe-Au core-satellite nanoparticles are excellent theranostic agents with multimodal imaging and photothermal capabilities.

Magnetic oxides are promising materials for alternative health diagnoses and treatments. The aim of this work is to understand the dependence of the heating power with the nanoparticle (NP) mean size, for the manganite composition La_0.75Sr_0.25MnO₃ (LSMO)—the one with maximum critical temperature for the whole La/Sr ratio of the series. We have prepared four different samples, each one annealed at different temperatures, in order to produce different mean NP sizes, ranging from 26 nm up to 106 nm. Magnetization measurements revealed a FC-ZFC irreversibility and from the coercive field as function of temperature we determined the blocking temperature. A phase diagram was delivered as a function of the NP mean size and, based on this, the heating mechanism understood. Small NPs (26 nm) is heated up within the paramagnetic range of temperature ($T>T_c$), and therefore provide low heating efficiency; while bigger NPs are heated up, from room temperature, within the magnetically blocked range of temperature ($T<T_B$), and also provide a small heating efficiency. The main finding of this article is related with the heating process for NPs within the magnetically unblocked range of temperature ($T_c>T>T_B$), for intermediate mean diameter size of 37 nm, with maximum efficiency of heat transfer.

We have developed a new core@shell composition system ZnFe₂O₄@MnFe₂O₄ for the full cycle of cancer treatment. During the study, the effect of the influence of particles on MRI diagnostics, radiotherapy and magnetic hyperthermia was evaluated.

Nanoparticle (NP) assisted magnetic hyperthermia (NMH) is a clinically proven method for cancer treatment. High-Z magnetic NPs could also be a perspective object for combining hyperthermia with tumor radiosensitization. However, this application of NPs is little studied, and it is unclear as to what particle compositions one can rely on. Therefore, the present work focuses on the search of materials that combine alternating magnetic field induced heating and high atomic number related dose enhancement abilities. A theoretical evaluation of 24 promising NP compositions was performed: the values of dose enhancement factor (DEF) were determined for kilovoltage x-ray spectra (30–300 kVp), as well as specific absorption rate (SAR) values were calculated for various combinations of elemental compositions and particle size distributions. For the alternating magnetic fields with amplitude $75\text{–}200\mathrm{Oe}$ and frequency $100\mathrm{kHz}$ , the maximum obtained SAR values ranged from 0.35 to $6000\mathrm{W}{\mathrm{g}}^{-1}$ , while DEF values for studied compounds ranged from 1.07 to 1.59. The increase in the monodispersity of NPs led to a higher SAR, confirming well-known experimental data. The four types of SAR dependences on external magnetic field amplitude and anisotropy constant were found for various particle sizes. The most predictable SAR behavior corresponds to larger NPs (∼70–100 nm). Thus, based on these calculations, the most promising for the combination of NMH with radiotherapy, from a physical point of view, are $\mathrm{L}{\mathrm{a}}_{0.75}\mathrm{S}{\mathrm{r}}_{0.25}\mathrm{Mn}{\mathrm{O}}_3$ , $\mathrm{G}{\mathrm{d}}_5\mathrm{S}{\mathrm{i}}_4$ , $\mathrm{SmC}{\mathrm{o}}_5$ , and $\mathrm{F}{\mathrm{e}}_{50}\mathrm{R}{\mathrm{h}}_{50}$ . The greatest dose enhancement is expected for superficial radiotherapy (in the voltage range up to ∼60 kVp).