High Magnetic Moment Research Articles

High-performance circularly polarized electroluminescence from d-f transition europium(II) complexes

Circularly polarized organic light-emitting diodes (CP-OLEDs) have attracted increasing interest for their advantages in generating circularly polarized light directly and efficiently. To date, chiral luminescent materials with different emission mechanisms have been investigated as emitters in CP-OLEDs, but it is difficult to achieve a high luminescence dissymmetry factor (g) and high efficiency simultaneously. Herein, chiral luminescent europium(II) complexes with d-f transition characteristics are synthesized and used as emitters in CP-OLEDs. The europium(II) complexes show a maximum g value of 6.6 × 10−3 in doped films, and the corresponding CP-OLEDs show a maximum external quantum efficiency up to 15.6%. The performance is attributed to the unique europium(II) complex with a d-f transition mechanism, which results in a theoretically high magnetic transition dipole moment and high exciton utilization efficiency. This study focusing on chiral d-f transition-containing lanthanide complexes opens up an avenue to future exploration of high-performance chiroptical materials.

Magnetism in single-layer of Zrse[formula omitted] by substituting 3[formula omitted] transition metals for Zr: Structural symmetry versus exchange splitting

To understand the magnetic properties of the novel two-dimensional materials and other phenomena which depend on electron correlation, finding the states located around Fermi energy (EF) and contributing to the correlated states of the system is basically important. In this paper, using the density functional theory, we investigate the electronic properties of substitution of 3d transition metal (TM) atoms for Zr in trigonal prismatic 2H and octahedral 1T structure of monolayer TM-doped ZrSe2 materials. The band structure, orbital projected density of states (DOS), and the number of electrons in the d-shell show that the correlated subspace depends strongly on the structural phase of the systems. The case of Mn substitution has the highest magnetic moment, 2.91 μB and 3.30 μB in 2H and 1T phases, respectively. In the 1T structure of Mn-doped ZrSe2, almost partially filled t2g impurity bands is well separated from eg states in the non-magnetic calculation, having a small bandwidth of about Wb= 0.4 eV. As a consequence, the strength of electron correlation U/Wb increases (U is effective on-site Coulomb interaction) and puts this compound in the moderately or strongly correlated regime, and causes a stronger electron spin separation than the 2H phase. In the 2H phase, the correlated states include two impurity bands with dominantly dxy and dx2−y2 characters and induce a smaller magnetic moment. Due to the large DOS of Mn and Cr atoms at the EF in both 1T and 2H structures, the Stoner criterion I.D(EF)>1 is satisfied, which is reasonably consistent with our results of ferromagnetic total energy calculations and the sizable magnetic moments.

Electrodeposited Conifex Magnetic Films with Low Magnetic Losses for Power Applications

Electromagnetic induction is essential for functioning of the analog circuits used in cell phones, MEMS devices and other power related electronics. In order to meet the demand of higher efficiency and minimum magnetic losses in packaging industry, we have developed solution chemistry1 , 2 for electrodeposition of CoNiFeX (X=S,O,P,B,V) thin films (thickness=500 nm) with high magnetic moment (HMM) and >500 permeability at >500 MHz frequency; >100μΩ-cm resistivity; >1.5 T magnetic moment. The CoNiFeX alloys are fully compatible with existing manufacturing concepts in semiconductor industry. Direct current (DC) and pulse current3 (PC) deposition methods for CoNiFeX alloys is employed to demonstrate control over BCC/FCC crystal structure by tuning transport conditions during electrodeposition. The structure of CoNiFeX alloys is characterized with average grain size of 15-20 nm which consequently yields coercivity values of CoNiFeX alloy films between 8-15 Oe at 500 nm thickness. CoNiFe alloys produced by DC and PC deposition have magnetic moment of 1.8 T, which is optimized to 2.2 T with addition of X (X=S,O,P,B,V) as additives4. More than 100% increase in the resistivity of deposited CoNiFe alloys is demonstrated with controlled concentration of additives and Fe3+ ions as oxide precipitating agent5 without reduction in magnetic properties. All samples exhibit shiny surface finish and low stress. Thin film inductor devices are fabricated with CoNiFeX alloys to test magnetic properties at >500 MHz frequency, which would be discussed with testing data. Brankovic, S. R., Vasiljevic, N., Klemmer, T. J. & Johns, E. C. Influence of additive adsorption on properties of pulse deposited CoFeNi alloys. Journal of the Electrochemical Society 152, C196 (2005).Brankovic, S. R., Sendur, K. & Klemmer, T. J. Magnetic Materials, Processes, and Devices VII and Electrodeposition of Alloys. in Proceedings of the International Symposia 2002, 269 (Electrochemical Society, 2003).Puippe, J.-C. & Leaman, F. Theory and practice of pulse plating. (Amer Electroplaters Soc, 1986).Djokić, S. S. Electrodeposition of amorphous alloys based on the iron group of metals. Journal of the Electrochemical Society 146, 1824 (1999).George, J. et al. Oxide/hydroxide incorporation into electrodeposited CoFe alloys—Consequences for magnetic softness. Electrochimica Acta 110, 411–417 (2013).

Robust room-temperature ferromagnetism induced by defect engineering in monolayer MoS2

Magnetism in two-dimensional materials is of great importance for exploring new physical phenomena and developing novel devices in nanoscale. It’s still a challenge to induce robust room temperature ferromagnetism in monolayer transition metal dichalcogen compound materials. In this paper, high quality monolayer MoS2 was prepared by chemical vapor deposition and low energy Cu ions were implanted into MoS2 via ion implantation. The surface morphology, chemical states, optical and magnetic properties were systematically investigated. Robust room-temperature ferromagnetism with saturation magnetization as high as 58 μB/Cu (∼2148 emu/cm3) was successfully induced in monolayer MoS2 after Cu implantation. Moreover, the magnetic properties are weakly temperature dependent, which is clearly the characteristic of defect-induced magnetism. First principles density functional theory calculations reveal that various structural defects, including nanohole, CuMo, Cui + VS and CuMo + VS can induce high magnetic moments. Meanwhile, CuMo and Cui + VS have lower formation energies and may contribute significantly to the extremely large magnetism in the implanted monolayer MoS2. Our work has demonstrated that through defects engineering by Cu implantation, robust room temperature ferromagnetism can be achieved in monolayer MoS2, which provides a potential way to induce large magnetization in other transition metal dichalcogen compound materials, and opens up new opportunities for their applications in nano-spintronics.

Unusually High Magnetic Moments Reported for the High-Spin Co2+ Ions at Axially Elongated CoO4X2 (X = Cl, Br, S, Se) Octahedral Sites: Overestimated Magnetic Moments Caused by Underestimated Magnetic Form Factors

An irreconcilable discrepancy between theory and experiment concerning the magnetic moments of the high-spin Co2+ (d7, S = 3/2) ions at the axially elongated CoO4X2 (X = Cl, Br, S, Se) octahedral sites was pointed out in our recent study [ Inorg. Chem. 2020, 59, 18319−18324]. The magnetic moments μobs of the Co2+ ions in materials containing the CoO4X2 units, determined from refinements of powder neutron diffraction patterns collected in their magnetically ordered states, were found to be notably larger than the spin-only moment of 3 μB (namely, 3.22–4.45 μB). Characteristically, the moments increase almost linearly with the bond-length ratio R = rCo–X/rCo–O, despite the fact that the orbital moments of the Co2+ ions are essentially quenched according to theoretical analyses and DFT + U + SOC computations. In this work, we probe the probable cause for the overestimation of magnetic moments in the ordered magnetic structures. We argue that the overestimated magnetic moments of the Co2+ ions and their increase with the bond-length ratio R originate from the underestimated magnetic form factors of the Co2+ ions at the CoO4X2 octahedral sites. The magnetic form factor F(q) of the Co2+ ion in each CoO4X2 octahedron is the Fourier transform of the magnetic moment distribution ρ(r) around the Co2+ ion, which is the electron density distribution associated with the magnetic orbitals (i.e., the singly occupied d-states) of the CoO4X2 octahedron. The conventional implementation of the magnetic form factor in refinement codes employed an approximation with a q-dependence calculated from the atomic wave function of the isolated ion. Since the spin moment distribution of ρ(r) at the axially elongated CoO4X2 (X = Cl, Br, S, Se) octahedral sites is delocalized from the Co2+ sites to its surrounding ligands, the moment distribution becomes anisotropic in shape. Use of the truncated and spherical approximation underestimates the form factor of the Co2+ ion, and its use in neutron diffraction refinements overestimates the magnetic moments. This effect becomes more pronounced as the moment density distribution is more delocalized along the Co–X direction.

Effects of atomic displacements on band gaps of Na2MgXO6 (X= Co, Fe) double perovskite oxides: GGA and GGA+U approaches

True half-metallic materials are among the most preferred material groups in spintronic applications with their 100% spin polarization. Perovskite materials have formed the basis of many semiconductor devices in recent years with their widespread technological use. In this study, Na2MgXO6 (X = Co, Fe) perovskite oxides were obtained as true half-metallic materials, and the effects of the atomic displacements between Mg and Co/Fe atoms on electronic, magnetic and half-metallic characters were investigated. First, volume-energy optimization curves were calculated, and ferromagnetic phases were energetically more stable. Second, electronic calculations were performed, and semiconducting band gaps were seen in the up-spin states. The band gaps of Na2MgCoO6 and Na2CoMgO6 oxides were obtained as 0.531 eV and 1.1446 eV, respectively. Then atomic displacements between Mg and Co/Fe-transition metals happened and band gaps of Na2MgFeO6 and Na2FeMgO6 oxides were obtained as 0.487 eV and 2.142 eV, respectively. As can be seen, the atomic structure changes directly affected the band gaps. Additionally, GGA + U interactions were performed for electronic calculations. As a result of increasing U-interactions, band gaps decreased. It is possible to say that all band gaps change with the effect of atomic compositions. Finally, the total magnetic moments of Na2MgCoO6 and Na2MgFeO6 oxides were obtained as 5.00 μB/f.u. and 6.00 μB/f.u., respectively. Na2MgXO6 (X = Co, Fe) oxides with half-metallic ferromagnetic features and high magnetic moment values are very useful materials for spintronic applications.

Human ACE2 Peptide-Attached Plasmonic-Magnetic Heterostructure for Magnetic Separation, Surface Enhanced Raman Spectroscopy Identification, and Inhibition of Different Variants of SARS-CoV-2 Infections.

The emergence of Alpha, Beta, Gamma, Delta, and Omicron variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for several million deaths up to now. Because of the huge amount of vaccine escape mutations in the spike (S) protein for different variants, the design of material for combating SARS-CoV-2 is very important for our society. Herein, we report on the design of a human angiotensin converting enzyme 2 (ACE2) peptide-conjugated plasmonic-magnetic heterostructure, which has the capability for magnetic separation, identification via surface enhanced Raman spectroscopy (SERS), and inhibition of different variant SARS-CoV-2 infections. In this work, plasmonic-magnetic heterostructures were developed using the initial synthesis of polyethylenimine (PEI)-coated Fe3O4-based magnetic nanoparticles, and then gold nanoparticles (GNPs) were grown onto the surface of the magnetic nanoparticles. Experimental binding data between ACE2-conjugated plasmonic-magnetic heterostructures and spike-receptor-binding domain (RBD) show that the Omicron variant has maximum binding ability, and it follows Alpha < Beta < Gamma < Delta < Omicron. Our finding shows that, due to the high magnetic moment (specific magnetization 40 emu/g), bioconjugated heterostructures are capable of effective magnetic separation of pseudotyped SARS-CoV-2 bearing the Delta variant spike from an infected artificial nasal mucus fluid sample using a simple bar magnet. Experimental data show that due to the formation of huge "hot spots" in the presence of SARS-CoV-2, Raman intensity for the 4-aminothiolphenol (4-ATP) Raman reporter was enhanced sharply, which has been used for the identification of separated virus. Theoretical calculations using finite-difference time-domain (FDTD) simulation indicate that, due to the "hot spots" formation, a six orders of magnitude Raman enhancement can be observed. A concentration-dependent inhibition efficiency investigation using a HEK293T-human cell line indicates that ACE2 peptide-conjugated plasmonic-magnetic heterostructures have the capability of complete inhibition of entry of different variants and original SARS-CoV-2 pseudovirions into host cells.

Above-room-temperature strong intrinsic ferromagnetism in 2D van der Waals Fe3GaTe2 with large perpendicular magnetic anisotropy

The absence of two-dimensional (2D) van der Waals (vdW) ferromagnetic crystals with both above-room-temperature strong intrinsic ferromagnetism and large perpendicular magnetic anisotropy (PMA) severely hinders practical applications of 2D vdW crystals in next-generation low-power magnetoelectronic and spintronic devices. Here, we report a vdW intrinsic ferromagnetic crystal Fe3GaTe2 that exhibits record-high above-room-temperature Curie temperature (Tc, ~350-380 K) for known 2D vdW intrinsic ferromagnets, high saturation magnetic moment (40.11 emu/g), large PMA energy density (~4.79 × 105 J/m3), and large anomalous Hall angle (3%) at room temperature. Such large room-temperature PMA is better than conventional widely-used ferromagnetic films like CoFeB, and one order of magnitude larger than known 2D vdW intrinsic ferromagnets. Room-temperature thickness and angle-dependent anomalous Hall devices and direct magnetic domains imaging based on Fe3GaTe2 nanosheet have been realized. This work provides an avenue for room-temperature 2D ferromagnetism, electrical control of 2D ferromagnetism and promote the practical applications of 2D-vdW-integrated spintronic devices.

Effects of B substitution for P on structure and magnetic properties of FePB amorphous alloys by first-principle investigation

Effects of the substitution of B for P on structure and magnetic properties of FePB amorphous alloys are investigated by first-principle molecular dynamics. Our analysis shows that Fe-centered polyhedra are mainly distorted icosahedral structures, and P- or B-centered polyhedra are mainly icosahedrons and triangular prisms. It is found that Fe80P5B15 amorphous alloy has the most 15xx bond pairs and higher local five-fold symmetry. With the increase of B atoms, magnetic moment of the amorphous alloy gradually increases, which is in good agreement with the experiments. Due to higher local symmetry, Fe80P5B15 amorphous alloy produces a larger splitting exchange energy and hence a higher magnetic moment. Fe atoms are easy to lose electrons to be positively charged, but B or P atoms are easily to gain electrons and are negatively charged. In addition, on account of the small radius of B atoms, more Fe atoms are aggregated locally in Fe80P5B15 amorphous alloy. The more the number of neighboring Fe atoms, the largrer the magnetic moment of Fe atoms is, which makes magnetic moment in amorphous alloys gradually increases. These findings provide intentional guidance for the development of new soft magnetic materials.

Modulation of the electronic and magnetic properties of pyridinic N-doped graphene with Ni/Cr

We have explored the interaction of Ni/Cr with pyridinic N-doped graphene and its influence on the electronic and magnetic characteristics of graphene using a density functional theory (DFT) approach. A [Formula: see text] graphene supercell with a single vacancy is modeled. Initially, the concentration of nitrogen atoms is varied in the pyridinic configuration of graphene. The structures, thus obtained, are decorated with Ni/Cr atoms. For configurations without transition metals (TMs), the calculated electronic band structures show a downward shift in Fermi level that decreases as nitrogen concentration increases. Furthermore, it is found that these structures manifest metallic behavior along with some flat bands near the Fermi level. With the addition of Ni/Cr atoms, the movement of the Fermi level toward the conduction band is noticed. The opening of the bandgap at the K-point also varies slightly with the concentration of N atoms and/or the presence of TM atoms. The structures P1N-Ni and P2N-Ni transmute into semiconductors. A significant increase in the magnetic moment is found with the adsorption of the Ni/Cr atom. The analysis of spin-polarized partial density of states proves that higher magnetic moments following TM absorption are mainly on account of the Ni/Cr-3d orbitals and their hybridization with C-2p orbitals. These findings suggest that functionalizing TMs on pyridinic N (Nitrogen)-doped graphene can drastically alter their electronic and magnetic properties.

Magneto-fluorescent contrast agents based on carbon Dots@Ferrite nanoparticles for tumor imaging

Bimodal magnetic-fluorescent materials for diagnostic imaging needs surface-engineered nanoparticles with great biosafety, pronounced colloidal stability, high magnetic moments, and strong photoluminescence (PL) emission. This work presents polymer-coated nanoparticles (PCNPs) based on manganese ferrites covered with a thin shell of nitrogen-doped carbon dots for magnetic-resonance and fluorescent dual mode imaging of cancerous tumors in vivo. An in situ thermolysis of metal oxalates and phenylenediamine in diphenyl ether allows for the facile synthesis of hybrid magneto-fluorescent nanoparticles. They possess an average size of 55 ± 5 nm with strong and excitation-independent PL emission at about 600 nm with a saturation magnetization of ∼ 19 emu/g. In vivo dispersion and biosafety of the hybrid nanoparticles are improved by a polymer-coating strategy with the aid of Tween polysorbate. In vitro studies for SK-OV-3 cells reveal that PCNPs are not toxic up to a high concentration of 125 µg/mL. H&E-stained sections of vital organs of animals treated with dosages of 5 mg/kg fail to present any histopathological changes after 24 h post-injection. The fluorescence intensity in the tumor tissue region appears to increases over time and the tumor becomes clearly visible after 60 min. Magnetic resonance imaging (MRI) of phantoms and animal cases also indicates the high efficiency of PCNPs as an T2 contrast agent in clinical diagnosis. Therefore, the developed PCNPs offer great potential for dual mode imaging of malignant tumors.

Spin and orbital transport in rare-earth dichalcogenides: The case of EuS2

We perform first-principles calculations to determine the electronic, magnetic, and transport properties of rare-earth dichalcogenides, taking a monolayer of $H$-phase ${\mathrm{EuS}}_{2}$ as a representative. We predict that the $H$ phase of the ${\mathrm{EuS}}_{2}$ monolayer exhibits a half-metallic behavior upon doping with a very high magnetic moment. We find that the electronic structure of ${\mathrm{EuS}}_{2}$ is very sensitive to the value of Coulomb repulsion $U$, which effectively controls the degree of hybridization between Eu $f$ and S $p$ states. We further predict that the nontrivial electronic structure of ${\mathrm{EuS}}_{2}$ directly results in a pronounced anomalous Hall effect with nontrivial band topology. Moreover, while we find that the spin Hall effect closely follows the anomalous Hall effect in the system, the orbital complexity of the system results in a very large orbital Hall effect, whose properties depend very sensitively on the strength of correlations. Our findings thus promote rare-earth-based dichalcogenides as a promising platform for topological spintronics and orbitronics.

Antiferromagnet-induced perpendicular magnetic anisotropy in ferromagnetic Co/Fe films with strong in-plane magnetic anisotropy

Ferromagnetic (FM) films with higher magnetic moment density typically exhibit sizable in-plane magnetic anisotropy as a result of strong dipolar interactions, which hinder their application in state-of-the-art perpendicularly based magnetic devices. This study reports the effects of triggering the perpendicular magnetic anisotropy (PMA) of a Co/Fe film with strong in-plane magnetic anisotropy through nearby antiferromagnetic (AFM) fcc ${\mathrm{Fe}}_{50}{\mathrm{Mn}}_{50}$ and face-centered tetragonal (e-fct) Mn films. Our results demonstrate that fcc ${\mathrm{Fe}}_{50}{\mathrm{Mn}}_{50}$ films with a three-dimensional quadratic AFM spin structure can trigger robust PMA in a Co/Fe film through collinearlike AFM-FM exchange coupling at room temperature. Furthermore, by incorporating a monolayered ${\mathrm{Fe}}_{50}{\mathrm{Mn}}_{50}$ film into the Mn-Co interface or by reducing the temperature, PMA can also be triggered in a Co/Fe film by using e-fct Mn films with an in-plane-oriented AFM spin structure at room or low temperature through noncollinear exchange coupling across the AFM-FM interface. Our results clarify the exchange-coupling mechanisms, characteristic behaviors, and critical conditions for increasing control over antiferromagnet-induced PMA in FM films with high magnetic moment density but strong in-plane magnetic anisotropy, which is helpful for the development of next-generation perpendicularly based spintronic devices.

Single-crystalline-level properties of ultrathin SrRuO3 flexible membranes with wide and clean surface

Transferring single-crystalline (SC) membranes to flexible substrates has been increasingly studied, enabling emerging functionality and enhanced performance of various devices. A commonly used support-assisted transfer process inevitably leaves dirty residue on material surfaces, limiting the further development of surface-related applications. Here, we scale down the thickness of flexible SC SrRuO3 (SRO) membranes to 15 nm with a clean surface area of 2.5 × 2.5 mm2. This is accomplished by making the polyethylene terephthalate (PET) substrate surface hydrophilic via oxygen plasma treatment, thereby reducing the surface tension. The ultrathin, clean, wide, and flexible SC SRO membranes guarantee a high transmittance of up to 60%, a low resistivity of 10−4−10−3 Ω cm at room temperature, and band ferromagnetism below 150 K with a high magnetic moment of ~0.5 μB/Ru at 10 K. The SC-level properties of our SRO membranes imply their potential use in state-of-the-art platforms for next-generation electronics and energy devices.

Colorless Magnetic Colloidal Particles Based on an Amorphous Metal‐Organic Framework Using Holmium as the Metal Species.

AbstractHolmium (Ho) is a lanthanide element with a high magnetic moment. Here, we create an amorphous metal‐organic framework (MOF) that has no long‐range periodic order but retains the basic components of MOF by using isophthalic acid as an organic linker and Ho as a metal species. The resulting spherical Ho‐MOF particles disperse well in a solvent and exhibit excellent magnetic properties in response to magnets. Since Ho has almost no coloring, Ho‐MOF particles are a colorless magnetic material, unlike conventional iron oxide particles. Taking advantage of the colorless property, the selective adsorption of dyes on Ho‐MOF particles can be easily visually confirmed by magnetically separating the particles. In addition, present versatile processes that enable adaptation of lanthanide elements other than Ho enable the development of colorless multifunctional MOF particles.

Magnetic Ranging Method for Horizontal Section Spacing Control of Cluster Wells

Summary Interwell fracture interactions are becoming an increasing problem with the large-scale exploitation of shale gas. High precision ranging technology is required for controlling the horizontal section spacing in cluster horizontal well drilling projects. The existing magnetic ranging technology has achieved remarkable application effects in the drilling engineering of twin horizontal wells, connected wells, and relief wells. But the maximum detection range cannot meet the needs of cluster horizontal well drilling engineering. A magnetic orientation sub connected to the nonmagnetic drill collar was designed to mark the position of the wellbore being drilled. Compared with the conventional magnetic sub connected to the drill bit, the magnetic orientation sub has a higher magnetic moment, is closer to the inclinometer, and has less effect on the build-up ability of the drilling tool. Although the effect of the magnetic orientation sub on the azimuth measurement is small when the azimuth angle is equal to 90° or 270°, the effect cannot be neglected in most cases. Therefore, we develop a computational model of the azimuth that considers the influence of the magnetic orientation sub. A new calculation model of distance and direction from the wellbore being drilled to the existing wellbore is developed to realize the ranging every 30 m or so. And the simulation experiment shows that the calculation accuracy of the distance and direction can meet the field needs of cluster horizontal well drilling engineering.

Regulating the Spin State of Single Noble Metal Atoms by Hydroxyl for Selective Dehydrogenation of CH4 Direct Conversion to CH3OH.

The key scientific challenge for methane (CH4) direct conversion to methanol (CH3OH) is considered to be the prevention of overoxidation of target products, which is restrained by the difficulty in the well-controlled process of selective dehydrogenation. Herein, we take single noble metal atom-anchored hexagonal boron nitride nanosheets with B vacancies (MSA/B1-xN) as the model materials and first propose that the dehydrogenation in the direct conversion of CH4 to CH3OH is highly dependent on the spin state of the noble metal. The results reveal that the noble metal with a higher spin magnetic moment is beneficial to the formation of the spin channels for electron transfer, which boosts the dissociation of C-H bonds. The promoted process of dehydrogenation will lead not only to the effective activation of CH4 but also to the easy overoxidation of CH3OH. More importantly, it is found that the spin state of noble metals can be regulated by the introduction of hydroxyl (OH), which realizes the selective dehydrogenation in the process of CH4 direct conversion to CH3OH. Among them, AgSA/B1-xN exhibits the best performance owing to the dynamic regulation spin state of a single Ag atom by OH. On the one hand, the introduction of OH significantly reduces the energy barrier of C-H bond dissociation by the increase in the spin magnetic moment. On the other hand, the high spin magnetic moment of a single Ag atom during the process of subsequent dehydrogenation can be modulated to nearly zero. As a result, the spin channel for electron transfer between the adsorbed CH3OH and reactive sites is broken, which hinders its overoxidation. This work opens a new path to designing catalysts for selective dehydrogenation by tuning the spin state of local electronic structures.

Wireless Force‐Inducing Neuronal Stimulation Mediated by High Magnetic Moment Microdiscs (Adv. Healthcare Mater. 6/2022)

Magnetomechanical Transduction In article number 2101826 by Rafael Morales, Gabriela Romero, and co-workers, magnetic microdiscs fabricated by litography techniques are utilized to magnetically induce mechanotransduction in primary neural cultures. The red and blue colors in the microdiscs indicate a magnetic component of a special spin configuration known as vortex state.

Preparation of holmium doped paramagnetic photoluminescence composite colloidal polymer particles through coordination induced self-assembly

Although composite magnetic materials based on iron oxide or ferric oxide have attracted much attention in both basic research and practical applications, the strong visible light absorption always limited their applications as optical or luminescent materials. Here we prepared paramagnetic photoluminescence composite colloidal polymer nanoparticles of P(PEGA)-b-P(AA-co-TPEE) by introducing holmium (Ho) to the assembly. The high magnetic moment of Ho endow paramagnetic behavior to the P(PEGA)-b-P(AA-co-TPEE)/Ho composite particles, and the saturation magnetization value of the P(PEGA)-b-P(AA-co-TPEE)/Ho increased with the increase content of Ho. Owing to the low chroma, Ho has little effect on the light absorption of polymer matrix and would not affect the photoluminescence (PL) behavior of TPEE block in the polymer chains. The coordination of Ho3+ and carboxyl groups decreased the hydrophilicity of PAA blocks, and induced the formation of composite colloidal nanoparticles with different morphologies. Therefore, the relationship between the PL intensity, Ho3+ concentration and saturation magnetization value of the composites could be built. In addition to be paramagnetic photoluminescence composite material, the P(PEGA)-b-P(AA-co-TPEE)/Ho composite particle can be used as a multifunctional carrier for fixed-point release under magnetic field, and can also be used for fluorescence imaging.

Simulation of antihydrogen deexcitation in neutral atom traps for improved trapping and cooling

We present results of simulations highlighting the performance of a cooling mechanism in a magnetic trap tailored for excited Rydberg atoms (or molecules) with high magnetic moment. Unlike previous work, the cooling is achieved through fast stimulated decay of inter-manifold transitions which optimizes the scheme. This mechanism is relevant to experiments with trapped antihydrogen atoms for which the trapping fraction is currently low. We find several-fold enhancements of the number of atoms trapped in the configurations probed.