Using Lorenz microscopy and small-angle electron diffraction, we directly present that the chiral magnetic soliton lattice (CSL) continuously evolves from a chiral helimagnetic structure in small magnetic fields in Cr(1/3)NbS2. An incommensurate CSL undergoes a phase transition to a commensurate ferromagnetic state at the critical field strength. The period of a CSL, which exerts an effective potential for itinerant spins, is tuned by simply changing the field strength. Chiral magnetic orders observed do not exhibit any structural dislocation, indicating their high stability and robustness in Cr(1/3)NbS2.

We investigate the interlayer magnetoresistance (MR) along the chiral crystallographic axis in the hexagonal chiral magnet CrNb 3 S 6 . In a region below the incommensurate-commensurate phase transition between the chiral soliton lattice and the forced ferromagnetic state, a negative MR is obtained in a wide range of temperature, while a small positive MR is found very close to the Curie temperature. Normalized data of the negative MR almost falls into a single curve and is well fitted by a theoretical equation of the soliton density, meaning that the origin of the MR is ascribed to the magnetic scattering of conduction electrons by a nonlinear, periodic, and countable array of magnetic soliton kinks. , belong to chiral space groups and are frequently referred to as chiral magnets. In chiral magnets, the combined effect of the symmetric Heisenberg exchange and the antisymmetric Dzyaloshinskii-Moriya (DM) interactions caused by the relativistic spin-orbit interaction [5,6] gives rise to a nontrivial spin texture and various interesting functions unique to chiral magnets. A coupling of conduction electrons with nontrivial spin textures has recently attracted great attention because of the ability to manipulate magnetotransport properties such as the topological Hall effect [7]. One promising candidate to realize this coupling is the chiral soliton lattice (CSL), which is formed in a chiral magnet under magnetic fields perpendicular to the chiral axis. The CSL is a nonlinear array of magnetic soliton kinks. It is naturally expected that each magnetic soliton kink works as a strong scattering potential for itinerant spins. Therefore, decreasing the number of magnetic soliton kinks may reduce the magnetoresistance (MR) and thus the CSL will present a nontrivial MR.In this Letter, we report the MR along the chiral axis in a hexagonal chiral magnetic crystal of CrNb 3 S 6 . We find that the normalized data of the negative MR almost falls into a single curve, and the revealed behavior indicates that the origin of the MR can be attributed to the magnetic scattering of conduction electrons by a nonlinear, periodic, and countable array of magnetic soliton kinks. Namely, we clarify the direct correlation between the experimentally measured MR and the analytically obtained soliton density as a function of the magnetic field.CrNb 3 S 6 is a typical monoaxial chiral magnet, which belongs to the space group of P6 3 22 [8]. It has a layered hexagonal structure of 2H-type NbS 2 intercalated by Cr atoms, so often expressed as Cr 1=3 NbS 2 . The size of the unit cell is 0.57 nm in the ab plane and 1.21 nm along the c axis [9,10]. Cr atoms are in the trivalent state and have localized electrons with spins of S ¼ 3=2, whereas conduction electrons are in an unfilled hybridized band of Nb and S. As a consequence of the chiral space group, the monoaxial DM interaction is allowed along the chiral c axis in CrNb 3 S 6 , which is given in the form of ÀD Á S 1 Â S 2 between localized neighboring spins S 1 and S 2 at Cr atoms. Here, D repres...

Nanoscale molecular rotors that can be driven in the solid state have been realized in Cs2([18]crown-6)3[Ni(dmit)2]2 crystals. To provide interactions between the molecular motion of the rotor and the electronic system, [Ni(dmit)2]- ions, which bear one S=1/2 spin on each molecule, were introduced into the crystal. Rotation of the [18]crown-6 molecules within a Cs2([18]crown-6)3 supramolecule above 220 K was confirmed using X-ray diffraction, NMR, and specific heat measurements. Strong correlations were observed between the magnetic behavior of the [Ni(dmit)2]- ions and molecular rotation. Furthermore, braking of the molecular rotation within the crystal was achieved by the application of hydrostatic pressure.

We present how macroscopically coherent ordering within a chiral state can be manifested in the physical properties within the context of an archetypical system-the chiral spin soliton lattice in a monoaxial chiral magnet CrNb 3 S 6. Using magnetotransport measurements and state-of-the-art Lorentz electron microscopy, we demonstrate spin soliton confinement in 1-μm-wide grains with different crystalline chirality and discretized magnetoresistance in 10-μm-wide crystals. Discretization effects are found to be prominent when the system size is reduced to the order of 10 μm along the chiral axis. A consequence that we identify is a robust coherence of the chiral soliton lattice against deformation. The spin configuration at the grain boundaries, which leads to soliton confinement, is experimentally clarified.

In view of renewed interest in multiferroic for molecular systems, we re-examine the structural and magnetic properties of the potentially ferroic layered perovskite-like (CH3NH3)2[Fe(II)Cl4] due to its high-temperature magnetic ordering transition. The structures from several sets of diffraction data of single crystals consist of square-grid layers of corner-sharing FeCl6 octahedra and changes from the high-symmetry I4/mmm (T > 335 K) to the low-symmetry Pccn (T < 335 K). In the former the iron and bridging chlorine atoms are within the layer and the organic cations sit in the middle of each square grid, while in the latter the octahedra are tilted in pairs, two in and two out, progressively by up to 12° and the nitrogen atoms follow their motion to be nearer to the two-in pairs. Crystals are stable up to 450 K and display three phase transitions, two structural at 332 and 233 K and one magnetic at 95 K. The temperature dependences of the dc magnetization (zero-field and field-cooling modes) in different applied fields (10-10,000 Oe) on several aligned single crystals independently reveal a hidden-canted antiferromagnetic ground state of at least four sublattices and not the reported canted antiferromagnetic ground state. A metamagnetic critical field of only 200 Oe transforms it to a canted antiferromagnet. The estimated canting angle is 1.4° in zero field, and it folds to ca. 2.8° in a field of 50 kOe at 2 K. The easy axis is along 010, the hard axis is along 100, and the intermediate and canting axis is 001. Using the available extracted parameters the phase diagram has been constructed. This study provides evidence of a complex and intricate manifestation of the orientation, temperature, and field dependence of the interplay between anisotropy and coherent lengths, which would need further studies.

We report the development of a molecular ferroelectric material inspired by the hexamethylenetetramine (hmta) non‐centrosymmetric molecular rotator. The bromide salt of diprotonated hmta (hmtaH2) crystalized as (hmtaH2)(NH4)Br3 in a metal‐free ABX3 perovskite‐type structure, in which the A and B sites are occupied by hmtaH22+ and ammonium cations, respectively. The compound crystallized in the Pma2 polar space group. A distorted polar perovskite structure formed owing to the distortion of {(NH4)Br6} octahedrons that are stabilized through the formation of NH⋅⋅⋅Br hydrogen bonds and the orientational ordering of positive charges on the non‐centrosymmetric hmtaH2 molecules. This spontaneous polarization exhibited ferroelectric behavior with a nominally high Curie temperature (>400 K), in which the electrical switching of polarization originates from the rotation of the hmtaH2 unit.

UV irradiation reversibly switches a new insulating and nonmagnetic molecular crystal, BPY[Ni(dmit)(2)](2) (BPY = N,N'-ethylene-2,2'-bipyridinium; Ni(dmit)(2) = bis(1,3-dithiole-2-thione-4,5-dithiolato)nickelate(III)), into a magnetic conductor. This is possible because the bipyridyl derivative cations (BPY(2+)) trigger a photochemical redox reaction in the crystal to produce a change of ∼10% in the filling of the Ni(dmit)(2) valence band, leaving localized spins on the BPY themselves. In the dark, almost all of the BPY molecules are closed-shell cations, and most of the Ni(dmit)(2) radical anions form spin-singlet pairs; thus, this material is a diamagnetic semiconductor. Under UV irradiation, a photocurrent is observed, which enhances the conductivity by 1 order of magnitude. Electron spin resonance measurements indicate that the UV irradiation reversibly generates carriers and localized spins on the Ni(dmit)(2) and the BPY, respectively. This high photoconductivity can be explained by charge transfer (CT) transitions between Ni(dmit)(2) and BPY in the UV region. In other words, the photoconduction and "photomagnetism" can be described as reversible optical control of the electronic states between an ionic salt (BPY(2+)/[Ni(dmit)(2)](-), nonmagnetic insulator) and a CT complex (BPY(2(1-δ)+)/[Ni(dmit)(2)]((1-δ)-) (δ ≈ 0.1), magnetic conductor) in the solid state.

In contrast to diradicals connected by alternant hydrocarbons, only a few studies on those connected by nonalternant hydrocarbons have been reported. The syntheses, structures, and magnetic properties of azulene-1,3-diyl linked bis(nitronyl nitroxide) (NN Az) and bis(iminonitroxide) (IN Az) diradicals and their Cu(hfac) (hfac=hexafluoroacetylacetonate) complexes were investigated. NN Az was shown to have an intramolecular ferromagnetic interaction with J /k =+10.0 K (H=-2JS ⋅S ) between (nitronyl nitroxide) spins, whereas IN Az was estimated to have a much weaker intramolecular magnetic interaction. The reactions of NN Az and IN Az with Cu(hfac) gave a 1:2 [{Cu(hfac) } (NN Az)] complex and a 1:1 [Cu(hfac) (IN Az)]⋅C H complex, respectively. [{Cu(hfac) } (NN Az)] showed strong intramolecular antiferromagnetic interactions (J /k ≈-800 K, J /k ≈-500 K) between the Cu spins and the coordinating NN spins, whereas [Cu(hfac) (IN Az)] exhibited a ferromagnetic exchange interaction (J /k =+114 K) between the Cu spin and the imino-coordinated iminonitroxide spin.