Magnetoelectric Coupling in a MnNa-Organic Complex under Pulsed Magnetic Fields up to 73 T.

Research on the magnetoelectric (ME) effect (or spin-electric coupling) in molecule-based magnetic materials is a relatively nascent but promising topic. Molecule-based magnetic materials have diverse magnetic functionalities that can be coupled to electrical properties. Here we investigate a realization of ME coupling that is fundamental but not heavily studied─the coupling of magnetic spin level crossings to changes in electric polarization.

High Field Electrical Polarization and Magnetoelectric Coupling in Chiral Magnet [Cu(pym)(HO)]SiF·HO.

The Heisenberg antiferromagnetic chain is a canonical model for understanding many-body gaps that emerge in quantum magnets, and as a result, there has been significant work on this class of materials for much of the past century. Chiral chains, on the other hand, have received markedly less attention. [Cu(pym)(HO)]SiF·HO (pym = pyrimidine) is an = 1/2 chiral antiferromagnet with an unconventional spin gap and no long-range ordering at zero field, features that distinguish it from more conventional spin chains that host simple phase diagrams and no magnetoelectric coupling.

Sudden adiabaticity signals reentrant bulk superconductivity in UTe.

There has been a recent surge of interest in UTe due to its unconventional magnetic field ()-reinforced spin-triplet superconducting phases persisting at fields far above the simple Pauli limit for . Magnetic fields in excess of 35 T then induce a field-polarized magnetic state via a first-order-like phase transition. More controversially, for field orientations close to and above 40 T, electrical resistivity measurements suggest that a further superconducting state may exist.

Continuous Spin Excitations in the Three-Dimensional Frustrated Magnet K_{2}Ni_{2}(SO_{4})_{3}.

Continuous spin excitations are widely recognized as one of the hallmarks of novel spin states in quantum magnets, such as quantum spin liquids (QSLs). Here, we report the observation of such kind of excitations in K_{2}Ni_{2}(SO_{4})_{3}, which consists of two sets of intersected spin-1 (Ni^{2+}) trillium lattices. Our inelastic neutron scattering measurement on single crystals clearly shows a dominant excitation continuum, which exhibits a distinct temperature-dependent behavior from that of spin waves, and is rooted in strong quantum spin fluctuations.

Near-Room-Temperature Magnetoelectric Coupling via Spin Crossover in an Iron(II) Complex.

Magnetoelectric coupling is achieved near room temperature in a spin crossover Fe molecule-based compound, [Fe(1bpp) ](BF ) . Large atomic displacements resulting from Jahn-Teller distortions induce a change in the molecule dipole moment when switching between high-spin and low-spin states leading to a step-wise change in the electric polarization and dielectric constant. For temperatures in the region of bistability, the changes in magnetic and electrical properties are induced with a remarkably low magnetic field of 3 T.

Accessing One-Dimensional Chains of Halogenoindates(III) in Organic-Inorganic Hybrids.

Organic-inorganic hybrids of halogenoindates(III) are typically represented by one of the zero-dimensional units: InX, InX, InX, or InX. Higher dimensional anionic forms, although not forbidden, have remained almost elusive. Here we report for the first time In-based organic-inorganic hybrids, (CHNS)InCl and (CHNS)InBr, with 1D anionic chains of -halide-bridged InX octahedra whose formation is guided by 2-mercaptopyrimidinium cations (CHNS).

Using Hyperoptimized Tensor Networks and First-Principles Electronic Structure to Simulate the Experimental Properties of the Giant {Mn} Torus.

The single-molecule magnet {Mn} is a challenge to theory because of its high nuclearity. We directly compute two experimentally accessible observables, the field-dependent magnetization up to 75 T and the temperature-dependent heat capacity, using parameter-free theory. In particular, we use first-principles calculations to derive short- and long-range exchange interactions and compute the exact partition function of the resulting classical Potts and Ising spin models for all 84 Mn = 2 spins to obtain observables.

Domain Wall Dynamics in a Ferroelastic Spin Crossover Complex with Giant Magnetoelectric Coupling.

Pinned and mobile ferroelastic domain walls are detected in response to mechanical stress in a Mn complex with two-step thermal switching between the spin triplet and spin quintet forms. Single-crystal X-ray diffraction and resonant ultrasound spectroscopy on [Mn(3,5-diCl-sal(323))]BPh reveal three distinct symmetry-breaking phase transitions in the polar space group series → → 1 → 1 The transition mechanisms involve coupling between structural and spin state order parameters, and the three transitions are Landau tricritical, first order, and first order, respectively. The two first-order phase transitions also show changes in magnetic properties and spin state ordering in the Jahn-Teller-active Mn complex.

Evidence of dynamical effects and critical field in a cobalt spin crossover complex.

The [Co(SQ)(4-CN-py)] complex exhibits dynamical effects over a wide range of temperature. The orbital moment, determined by X-ray magnetic circular dichroism (XMCD) with decreasing applied magnetic field, indicates a nonzero critical field for net alignment of magnetic moments, an effect not seen with the spin moment of [Co(SQ)(4-CN-py)].

Thermal and Magnetic Field Switching in a Two-Step Hysteretic Mn Spin Crossover Compound Coupled to Symmetry Breakings.

A Mn spin crossover complex with atypical two-step hysteretic thermal switching at 74 K and 84 K shows rich structural-magnetic interplay and magnetic-field-induced spin state switching below 14 T with an onset below 5 T. The spin states, structures, and the nature of the phase transitions are elucidated via X-ray and magnetization measurements. An unusual intermediate phase containing four individual sites, where are in a pure low spin state, is observed.

Domain Wall Patterning and Giant Response Functions in Ferrimagnetic Spinels.

The manipulation of mesoscale domain wall phenomena has emerged as a powerful strategy for designing ferroelectric responses in functional devices, but its full potential is not yet realized in the field of magnetism. This work shows a direct connection between magnetic response functions in mechanically strained samples of Mn O and MnV O and stripe-like patternings of the bulk magnetization which appear below known magnetostructural transitions. Building off previous magnetic force microscopy data, a small-angle neutron scattering is used to show that these patterns represent distinctive magnetic phenomena which extend throughout the bulk of two separate materials, and further are controllable via applied magnetic field and mechanical stress.

Field-tunable toroidal moment in a chiral-lattice magnet.

Ferrotoroidal order, which represents a spontaneous arrangement of toroidal moments, has recently been found in a few linear magnetoelectric materials. However, tuning toroidal moments in these materials is challenging. Here, we report switching between ferritoroidal and ferrotoroidal phases by a small magnetic field, in a chiral triangular-lattice magnet BaCoSiO with tri-spin vortices.

Giant Magnetoelectric Coupling and Magnetic-Field-Induced Permanent Switching in a Spin Crossover Mn(III) Complex.

We investigate giant magnetoelectric coupling at a Mn spin crossover in [MnL]BPh (L = (3,5-diBr-sal)323) with a field-induced permanent switching of the structural, electric, and magnetic properties. An applied magnetic field induces a first-order phase transition from a high spin/low spin (HS-LS) ordered phase to a HS-only phase at 87.5 K that remains after the field is removed.

Three Jahn-Teller States of Matter in Spin-Crossover System Mn(taa).

Three high-spin phases recently discovered in the spin-crossover system Mn(taa) are identified through analysis by a combination of first-principles calculations and Monte Carlo simulation as a low-temperature Jahn-Teller ordered (solid) phase, an intermediate-temperature dynamically correlated (liquid) phase, and an uncorrelated (gas) phase. In particular, the Jahn-Teller liquid phase arises from competition between mixing with low-spin impurities, which drive the disorder, and intermolecular strain interactions. The latter are a key factor in both the spin-crossover phase transition and the magnetoelectric coupling.

Magnetoelectric behavior via a spin state transition.

In magnetoelectric materials, magnetic and dielectric/ferroelectric properties couple to each other. This coupling could enable lower power consumption and new functionalities in devices such as sensors, memories and transducers, since voltages instead of electric currents are sensing and controlling the magnetic state. We explore a different approach to magnetoelectric coupling in which we use the magnetic spin state instead of the more traditional ferro or antiferromagnetic order to couple to electric properties.

Measurement of the angle dependence of magnetostriction in pulsed magnetic fields using a piezoelectric strain gauge.

We present a high resolution method for measuring magnetostriction in millisecond pulsed magnetic fields at cryogenic temperatures with a sensitivity of . The sample is bonded to a thin piezoelectric plate such that when the sample's length changes, it strains the piezoelectric and induces a voltage change. This method is more sensitive than a fiber-Bragg grating method.

Anomalous Metamagnetism in the Low Carrier Density Kondo Lattice YbRhSi.

We report complex metamagnetic transitions in single crystals of the new low carrier Kondo antiferromagnet . Electrical transport, magnetization, and specific heat measurements reveal antiferromagnetic order at . Neutron diffraction measurements show that the magnetic ground state of is a collinear antiferromagnet, where the moments are aligned in the plane.

Fiber Bragg Grating Dilatometry in Extreme Magnetic Field and Cryogenic Conditions.

In this work, we review single mode SiO₂ fiber Bragg grating techniques for dilatometry studies of small single-crystalline samples in the extreme environments of very high, continuous, and pulsed magnetic fields of up to 150 T and at cryogenic temperatures down to <1 K. Distinct millimeter-long materials are measured as part of the technique development, including metallic, insulating, and radioactive compounds. Experimental strategies are discussed for the observation and analysis of the related thermal expansion and magnetostriction of materials, which can achieve a strain sensitivity () as low as a few parts in one hundred million (≈10).

Magnetic Ordering-Induced Multiferroic Behavior in [CH3NH3][Co(HCOO)3] Metal-Organic Framework.

We present the first example of magnetic ordering-induced multiferroic behavior in a metal-organic framework magnet. This compound is [CH3NH3][Co(HCOO)3] with a perovskite-like structure. The A-site [CH3NH3](+) cation strongly distorts the framework, allowing anisotropic magnetic and electric behavior and coupling between them to occur.

Bose glass and Mott glass of quasiparticles in a doped quantum magnet.

The low-temperature states of bosonic fluids exhibit fundamental quantum effects at the macroscopic scale: the best-known examples are Bose-Einstein condensation and superfluidity, which have been tested experimentally in a variety of different systems. When bosons interact, disorder can destroy condensation, leading to a 'Bose glass'. This phase has been very elusive in experiments owing to the absence of any broken symmetry and to the simultaneous absence of a finite energy gap in the spectrum.

[Ni(HF2)(3-Clpy)4]BF4 (py = pyridine): evidence for spin exchange along strongly distorted F···H···F- bridges in a one-dimensional polymeric chain.

[Ni(HF(2))(3-Clpy)(4)]BF(4) (py = pyridine) is a simple one-dimensional (1D) coordination polymer composed of compressed NiN(4)F(2) octahedra that form chains with bridging HF(2)(-) ligands. In spite of significant distortion of the HF(2)(-) bridge, a quasi-1D antiferromagnetic (AFM) behavior was observed with J(FHF) = 4.86 K.