Permanent Electride Magnets Induced by Quasi-Atomic Non-Nucleus-Bound Electrons

Interstitial quasi-atomic electrons (IQEs) in the quantized energy levels of positively charged cavities possess a substantial own magnetic moment and control the magnetism of crystalline electrides depending on the interaction with surrounding cations. However, weak spin-orbit coupling and gentle exchange interaction restricted by the IQEs preclude a large magnetic anisotropic, remaining a challenge for a hard magnetism. It is reported that 2D [Re2C]2+·2e- electrides (Re = Er, Ho, Dy, and Tb) show the permanent magnetism in a ferrimagnetic ground state, mimicking the ferrites composed of magnetic sublattices with different spin polarizations. Magnetic interaction between Re-spin lattice and IQE-spin lattice in the [Re2C]2+·2e- electrides results in a large magnetocrystalline anisotropy and high coercivity, giving a maximum energy product of 15 MGOe. It is demonstrated that the spontaneous breaking of magnetic IQE-sublattice through substitution with paramagnetic elements produces a crossover into an antiferromagnetic spin ordering of Re-sublattice, implying that the magnetic sublattice of IQEs drives the permanent magnetism.

Two-dimensional nanomaterials based on rare earth elements for biomedical applications

As a kind of star materials, two-dimensional (2D) nanomaterials have attracted tremendous attention for their unique structures, excellent performance and wide applications. In recent years, layered rare earth-based or doped nanomaterials have become a new important member of the 2D nanomaterial family and have attracted significant interest, especially layered rare earth hydroxides (LREHs) and layered rare earth-doped perovskites with anion-exchangeability and exfoliative properties. In this review, we systematically summarize the synthesis, exfoliation, fabrication and biomedical applications of 2D rare earth nanomaterials. Upon exfoliation, the LREHs and layered rare earth-doped perovskites can be dimensionally reduced to ultrathin nanosheets which feature high anisotropy and flexibility. Subsequent fabrication, especially superlattice assembly, enables rare earth nanomaterials with diverse compositions and structures, which further optimizes or even creates new properties and thus expands the application fields. The latest progress in biomedical applications of the 2D rare earth-based or doped nanomaterials and composites is also reviewed in detail, especially drug delivery and magnetic resonance imaging (MRI). Moreover, at the end of this review, we provide an outlook on the opportunities and challenges of the 2D rare earth-based or doped nanomaterials. We believe this review will promote increasing interest in 2D rare earth materials and provide more insight into the artificial design of other nanomaterials based on rare earth elements for functional applications.

Macroscopic Gradient Ordered α-Fe/Pr2Fe14B Nanocomposites with Ultrahigh Energy Density

Nanoparticle self-assembly enables the generation of complex ordered nanostructures with enhanced properties or new functionalities. However, the ordering is often limited to the micrometer scale with chemical strategies due to the relative weak supramolecular interactions that govern the self-assembly process. Here a physical strategy via temperature-gradient-assisted self-assembly is reported to create three-dimensional (3D) macroscopic ordered nanocomposites with different gradient variations in grain size, constituent content, and crystal orientation. The resulting α-Fe/Pr₂Fe₁₄B ordered nanostructure with reverse gradients in both the grain size and α-Fe content exhibits a record-high energy density of about 25 MGOe for isotropic α-Fe/Pr₂Fe₁₄B systems, approximately 130% higher than that of its disordered counterpart. Both experiments and micromagnetic simulations demonstrate that creating ordered nanostructures is an alternative approach to develop high-performance permanent-magnet materials. Our findings make a significant step toward creating 3D macroscopic ordered nanostructures and will stimulate the development of ordered nanomaterials.

Magnetic Nanostructures: Rational Design and Fabrication Strategies toward Diverse Applications

In recent years, the continuous development of magnetic nanostructures (MNSs) has tremendously promoted both fundamental scientific research and technological applications. Different from the bulk magnet, the systematic engineering on MNSs has brought a great breakthrough in some emerging fields such as the construction of MNSs, the magnetism exploration of multidimensional MNSs, and their potential translational applications. In this review, we give a detailed description of the synthetic strategies of MNSs based on the fundamental features and application potential of MNSs and discuss the recent progress of MNSs in the fields of nanomedicines, advanced nanobiotechnology, catalysis, and electromagnetic wave adsorption (EMWA), aiming to provide guidance for fabrication strategies of MNSs toward diverse applications.

Rare-Earth Doping in Nanostructured Inorganic Materials

Impurity doping is a promising method to impart new properties to various materials. Due to their unique optical, magnetic, and electrical properties, rare-earth ions have been extensively explored as active dopants in inorganic crystal lattices since the 18th century. Rare-earth doping can alter the crystallographic phase, morphology, and size, leading to tunable optical responses of doped nanomaterials. Moreover, rare-earth doping can control the ultimate electronic and catalytic performance of doped nanomaterials in a tunable and scalable manner, enabling significant improvements in energy harvesting and conversion. A better understanding of the critical role of rare-earth doping is a prerequisite for the development of an extensive repertoire of functional nanomaterials for practical applications. In this review, we highlight recent advances in rare-earth doping in inorganic nanomaterials and the associated applications in many fields. This review covers the key criteria for rare-earth doping, including basic electronic structures, lattice environments, and doping strategies, as well as fundamental design principles that enhance the electrical, optical, catalytic, and magnetic properties of the material. We also discuss future research directions and challenges in controlling rare-earth doping for new applications.

Sandwiched CoFe2O4/SrFe11.5Al0.5O19/CoFe2O4 nanoparticles with exchange-coupling effect

Exchange-coupled hard/soft ferrite nanoparticles are prospective to squeeze out a part of expensive magnets based on rare-earth elements. However, the known exchange-coupled composite ferrite nanoparticles often suffer from the lack of a powerful enough hard magnetic core, high defectivity of magnetic phases, and a poor interface between them. Herein, we demonstrate the first efficient synthesis of sandwiched nanomagnets, which exhibit a pronounced exchange-coupling effect. This work is featured by the use of individual highly coercive strontium hexaferrite nanoplates prepared by a borate glass crystallization method as cores for the composite particles. The high crystal quality of the hexaferrite cores as the substrate promotes the epitaxial growth of CoFe₂O₄ layers on the 001 facets from an organic high-boiling solvent and results in the enhancement of the remanent magnetization and maximum energy product of the composite material. The results of this work open new prospects for the fabrication of multilayer oxide heterostructures with synergetic performance, which expands the applications of exchange-coupled composites.

Tip Interface Exchange-Coupling Based on "Bi-Anisotropic" Nanocomposites with Low Rare-Earth Content

Specially designed SmCo₅/Co magnetic nanocomposites have been fabricated by a "bottom up" process. SmCo₅ nanochips were first prepared by solution-phase chemical synthesis combined with reductive annealing and then coated by chemical deposition of Co nanorods. Both the SmCo₅ nanochips and Co nanorods are anisotropic and could be simultaneously aligned under the external magnetic field. Magnetic measurements applied on these "bi-anisotropic" SmCo₅/Co composites show high magnetic performance with the Co phase content in a wide range from 10 to 80 wt %. For the first time ever, the applicable exchange-coupled nanocomposites with a rare-earth content lower than 7 wt % was realized, which exhibits the coercivity close to 10 kOe and remanence 31% larger than that of single phase SmCo₅. 3-D micromagnetic simulations were performed to reveal that the reversal mechanism in the Co phase was transferred from the incoherent mode to the coherent mode under a tip interface exchange-coupling with a SmCo₅ surface.

Halogen regulation triggers NLO and dielectric dual switches in hybrid compounds with green fluorescence

An effective strategy of using halogens to modify organic–inorganic hybrid materials to obtain NLO switching characteristics, which is expected to be used for the directional adjustment of NLO switch activity.