Orthoborates LiCdRE₅(BO₃)₆ (RE = Sm–Lu and Y) with Rare-Earth Ions on a Triangular Lattice: Synthesis, Crystal Structure, and Optical and Magnetic Properties

Single crystals of LiCdY₅(BO₃)₆ were successfully grown from a Li₂O–B₂O₃ flux, and its lanthanide homotypic compounds, LiCdRE₅(BO₃)₆ (RE = Sm–Lu), have been prepared by solid-state reaction. They crystallize in the noncentrosymmetric space group <i>P</i>6₅22 with cell parameters in the ranges of <i>a</i> = 7.0989(2)–6.9337(1) Å and <i>c</i> = 25.9375(1)–24.8960(6) Å. As a representative example, LiCdY₅(BO₃)₆ features a triangular lattice in the <i>ab</i> plane composed of three distinct crystallographic Y sites. The triangular lattices spaced with the same distance of 16<i>c</i> are further stacked to build three-dimensional frameworks by reinforcement of the isolated planar BO₃ groups and distorted LiO₄ tetrahedra. Magnetic measurements show that Eu and Sm compounds exhibit typical Van Vleck-type paramagnetism and other rare-earth borates show weak antiferromagnetic behavior. In addition, UV–vis–near-IR diffuse-reflectance and photoluminescence spectra were performed to understand the transition energy levels of active rare-earth ions and their relationships to magnetism

Observation of Resonant Quantum Magnetoelectric Effect in a Multiferroic Metal–Organic Framework

A resonant quantum magnetoelectric coupling effect has been demonstrated in the multiferroic metal–organic framework of [(CH₃)₂NH₂]­Fe­(HCOO)₃. This material shows a coexistence of a spin-canted antiferromagnetic order and ferroelectricity as well as clear magnetoelectric coupling below <i>T</i>_N ≈ 19 K. In addition, a component of single-ion quantum magnets develops below ∼8 K because of an intrinsic magnetic phase separation. The stair-shaped magnetic hysteresis loop at 2 K signals resonant quantum tunneling of magnetization. Meanwhile, the magnetic field dependence of dielectric permittivity exhibits sharp peaks just at the critical tunneling fields, evidencing the occurrence of resonant quantum magnetoelectric coupling effect. This resonant effect enables a simple electrical detection of quantum tunneling of magnetization

Observation of Resonant Quantum Magnetoelectric Effect in a Multiferroic Metal–Organic Framework

A resonant quantum magnetoelectric coupling effect has been demonstrated in the multiferroic metal–organic framework of [(CH₃)₂NH₂]­Fe­(HCOO)₃. This material shows a coexistence of a spin-canted antiferromagnetic order and ferroelectricity as well as clear magnetoelectric coupling below <i>T</i>_N ≈ 19 K. In addition, a component of single-ion quantum magnets develops below ∼8 K because of an intrinsic magnetic phase separation. The stair-shaped magnetic hysteresis loop at 2 K signals resonant quantum tunneling of magnetization. Meanwhile, the magnetic field dependence of dielectric permittivity exhibits sharp peaks just at the critical tunneling fields, evidencing the occurrence of resonant quantum magnetoelectric coupling effect. This resonant effect enables a simple electrical detection of quantum tunneling of magnetization

Observation of Magnetodielectric Effect in a Dysprosium-Based Single-Molecule Magnet

Materials that possess coupled magnetic and electric properties are of significant interest because of their potential use in next-generation magnetoelectric devices such as digital information storage. To date, the magnetoelectric materials that have been studied in-depth have been limited mainly to inorganic oxides such as perovskite oxides. Molecular materials are a promising alternative because their magnetic and electric elements can be combined together at the molecular level via relatively simple molecular designs. Here, we report the coupling of magnetic and electric properties through a magnetodielectric (MD) effect in a single-crystal sample, which is constructed from dysprosium­(III) single-molecule magnets (SMMs). The MD effect originates from intrinsic spin–lattice coupling of the dysprosium­(III) ion within the sample. This is the first observation of the MD effect in a SMM-based material, which could pave the way toward the synthesis of advanced materials that combine distinct magnetic and electric properties using molecular chemistry for use in molecular devices with nanoscale size

Observation of Magnetodielectric Effect in a Dysprosium-Based Single-Molecule Magnet

Materials that possess coupled magnetic and electric properties are of significant interest because of their potential use in next-generation magnetoelectric devices such as digital information storage. To date, the magnetoelectric materials that have been studied in-depth have been limited mainly to inorganic oxides such as perovskite oxides. Molecular materials are a promising alternative because their magnetic and electric elements can be combined together at the molecular level via relatively simple molecular designs. Here, we report the coupling of magnetic and electric properties through a magnetodielectric (MD) effect in a single-crystal sample, which is constructed from dysprosium­(III) single-molecule magnets (SMMs). The MD effect originates from intrinsic spin–lattice coupling of the dysprosium­(III) ion within the sample. This is the first observation of the MD effect in a SMM-based material, which could pave the way toward the synthesis of advanced materials that combine distinct magnetic and electric properties using molecular chemistry for use in molecular devices with nanoscale size

Enhanced Catalytic Activities of NiPt Truncated Octahedral Nanoparticles toward Ethylene Glycol Oxidation and Oxygen Reduction in Alkaline Electrolyte

The high cost and poor durability of Pt nanoparticles (NPs) are great limits for the proton exchange membrane fuel cells (PEMFCs) from being scaled-up for commercial applications. Pt-based bimetallic NPs together with a uniform distribution can effectively reduce the usage of expensive Pt while increasing poison resistance of intermediates. In this work, a simple one-pot method was used to successfully synthesize ultrafine (about 7.5 nm) uniform NiPt truncated octahedral nanoparticles (TONPs) in dimethylformamid (DMF) without any seeds or templates. The as-prepared NiPt TONPs with Pt-rich surfaces exhibit greatly improved catalytic activities together with good tolerance and better stability for ethylene glycol oxidation reaction (EGOR) and oxygen reduction reaction (ORR) in comparison with NiPt NPs and commercial Pt/C catalysts in alkaline electrolyte. For example, the value of mass and specific activities for EGOR are 23.2 and 17.6 times higher comparing with those of commercial Pt/C, respectively. Our results demonstrate that the dramatic enhancement is mainly attributed to Pt-rich surface, larger specific surface area, together with coupling between Ni and Pt atoms. This developed method provides a promising pathway for simple preparation of highly efficient electrocatalysts for PEMFCs in the near future

Strain-Mediated Coexistence of Volatile and Nonvolatile Converse Magnetoelectric Effects in Fe/Pb(Mg_1/3Nb_2/3)_0.7Ti_0.3O₃ Heterostructure

Strain-mediated ferromagnetic/ferroelectric (FE) heterostructures have played an important role in multiferroic materials to investigate the electric-field control of magnetism in the past decade, due to their excellent performances, such as room-temperature operation and large magnetoelectric (ME) coupling effect. Because of the different FE-switching-originated strain behaviors and varied interfacial coupling effect, both loop-like (nonvolatile) and butterfly-like (volatile) converse ME effects have been reported. Here, we investigate the electric-field control of magnetism in a multiferroic heterostructure composed of a polycrystalline Fe thin film and a Pb­(Mg_1/3Nb_2/3)_0.7Ti_0.3O₃ single crystal, and the experimental results exhibit complex behaviors, suggesting the coexistence of volatile and nonvolatile converse ME effects. By separating the symmetrical and antisymmetrical parts of the electrical modulation of magnetization, we distinguished the loop-like hysteresis and butterfly-like magnetization changes tuned by electric fields, corresponding to the strain effects related to the FE 109° switching and 71/180° switching, respectively. Further magnetic-field-dependent as well as angular-dependent investigation of the converse ME effect confirmed the strain-mediated magnetism involving competition among the Zeeman energy, magnetocrystalline anisotropy energy, and strain-generated magnetoelastic energy. This study is helpful for understanding the electric-field control of magnetism in multiferroic heterostructures as well as its relevant applications

Real-Space Observation of Nonvolatile Zero-Field Biskyrmion Lattice Generation in MnNiGa Magnet

Magnetic skyrmions, particular those without the support of external magnetic fields over a wide temperature region, are promising as alternative spintronic units to overcome the fundamental size limitation of conventional magnetic bits. In this study, we use in situ Lorentz microscope to directly demonstrate the generation and sustainability of robust biskyrmion lattice at zero magnetic field over a wide temperature range of 16–338 K in MnNiGa alloy. This procedure includes a simple field-cooling manipulation from 360 K (higher than Curie temperature <i>T</i>_C ∼ 350 K), where topological transition easily occurs by adapting the short-range magnetic clusters under a certain magnetic field. The biskyrmion phase is favored upon cooling below <i>T</i>_C. Once they are generated, the robust high-density biskyrmions persist even after removing the external magnetic field due to the topological protection and the increased energy barrier