Optical control of physical properties and functionalities is an attractive area of research in the development of advanced optical materials. Here, we report a magnet that can switch the ...polarization plane of light by 90° under optical stimulation. The magnet is a chiral structured iron-octacyanoniobate, and its magnetic properties can be reversibly switched by irradiating with blue and red light, which causes light-reversible spin-crossover on the iron(II) ion. Using this material, second-harmonic generation, a nonlinear optical effect, was investigated. The vertical polarization plane was switched to horizontal polarization by irradiating with blue light, and was then returned to the original vertical polarization by irradiating with red light. This phenomenon originates from alternate optical switching between crystallographic and magnetic contributions to second-harmonic generation within the magnet, where the chiral structure and photomagnetism are coupled. The observed perpendicular optical switching should encourage studies in the fields of magneto-optical memory and optoelectronic devices.
Ionic conductors serve as solid electrolytes for fuel cells and batteries, whereas polar crystals such as ferroelectrics and pyroelectrics-which are typically insulating materials-are used in ...electronic devices. Here we show a material that combines superionic conductivity with a polar crystal structure at room temperature. This three-dimensional anionic network is based on -Fe-N≡C-Mo- units, with Cs cations hosted in every other pore. In the resulting Cs
Fe
Mo(CN)
(NO)·4H
O material, the negative and positive charges of the framework and Cs
ions, respectively, are non-symmetrically shifted in the c-axis direction of the unit cell, and spontaneous electric polarization is generated, in turn leading to second harmonic generation (SHG). Additionally, this material is a superionic conductor (with an ionic conductivity value of 4 × 10
S cm
at 318 K). Furthermore, the ionic conductivity significantly decreases under 532 nm light irradiation (from 1 × 10
S cm
to 6 × 10
S cm
at room temperature) and, when irradiation stops, returns to its original value within ~1 h.
Nitrosyl metal complexes (M–NO), in which nitrosyl ligands are coordinated to transition-metal ions, have been studied from the viewpoints of physiological activity, catalytic activity, and ...photosensitivity. The structural flexibility and electric polarization of the nitrosyl ligand are attractive characteristics. Herein we show a photoswitchable nonlinear-optical (NLO) crystal based on a dysprosium–iron nitrosyl assembly. This crystal is composed of a one-dimensional chain structure in the polar Pna21 space group. Because of spontaneous electric polarization, it exhibits a NLO effect of second harmonic generation (SHG). The SHG signal reversibly changes by alternate irradiation with 473 and 804 nm laser lights. The observed photoreversible switching effect on SHG is caused by photoinduced linkage isomerization of the metal nitrosyl sites, i.e., MN+O ↔ MON+. Such an optically switchable NLO crystal should be useful for optical devices such as optical filters and optical shutters as well as probes in SHG microscopy.
Commonly available heat-storage materials cannot usually store the energy for a prolonged period. If a solid material could conserve the accumulated thermal energy, then its heat-storage application ...potential is considerably widened. Here we report a phase transition material that can conserve the latent heat energy in a wide temperature range, T<530 K and release the heat energy on the application of pressure. This material is stripe-type lambda-trititanium pentoxide, λ-Ti3O5, which exhibits a solid-solid phase transition to beta-trititanium pentoxide, β-Ti3O5. The pressure for conversion is extremely small, only 600 bar (60 MPa) at ambient temperature, and the accumulated heat energy is surprisingly large (230 kJ L(-1)). Conversely, the pressure-produced beta-trititanium pentoxide transforms to lambda-trititanium pentoxide by heat, light or electric current. That is, the present system exhibits pressure-and-heat, pressure-and-light and pressure-and-current reversible phase transitions. The material may be useful for heat storage, as well as in sensor and switching memory device applications.
Self-assembly of Er(
iii
) ions with octacyanidotungstate(
v
) in the presence of pure
N
,
N
-dimethylacetamide (dma) resulted in the formation of one-dimensional zigzag chain {Er
III
(dma)
5
W
V
...(CN)
8
}
n
(
1
). Coordination polymer
1
crystallizes in the non-centrosymmetric space group
P
2
1
and it exhibits second harmonic generation (SHG) effect with SH susceptibility of 5.8 × 10
−11
esu. Interestingly, the treatment of
1
with small amount of water results in the generation of another complex salt Er
III
(dma)
5
(H
2
O)
2
·W
V
(CN)
8
·dma·H
2
O (
2
) which crystallizes in centrosymmetric space groups of
P
2
1
/
n
, disqualifying the occurrence of SHG phenomenon. On the other hand, the elimination of cyanido-bridges and formation of seven-coordinated erbium(
iii
) centre resulted in magnetic field induced single molecule magnet (SMM) behaviour with effective energy barrier of 28.6(3) K for
2
. Finally, self-assembly of Er(
iii
) with octacyanidotungstate(
v
) in water/dma mixture gave a complex salt Er
III
(dma)
4
(H
2
O)
3
·W
V
(CN)
8
·dma·3H
2
O (
3
) similar to
2
. Dynamic magnetic studies reveal that
3
is also showing slow magnetic relaxation, however, the substitution of single dma by water molecule induces the change in the local geometry of Er(
iii
) centre leading to weak SMM properties for
3
.
Studies of {Er(dma)
5
W(CN)
8
}
n
(
1
) showing nonlinear optical effect of second harmonic generation, and Er(dma)
5
(H
2
O)
2
·W(CN)
8
·dma·H
2
O (
2
) and Er(dma)
4
(H
2
O)
3
·W(CN)
8
·dma·3H
2
O (
3
) revealing field-induced single molecule magnet behavior.
One-dimensional zigzag cyanido-bridged coordination polymers have been prepared as a result of self-assembly of lanthanide(III) ions with octacyanidotungstate(V) anions in the presence of ...N,N-dimethylacetamide (dma). All compounds crystallized in noncentrosymmetric space group P21 with a molecular formula of LnIII(dma)5WV(CN)8 Ln = Gd (1), Tb (2), Dy (3), Ho (4), Er (5), Tm (6), Yb (7), Lu (8), or Y (9). Magnetic studies revealed weak antiferromagnetic interactions through LnIII–NC–WV bridges and the formation of ferrimagnetically coupled chains at very low temperatures. Moreover, temperature dependencies of magnetic susceptibilities were fitted using the crystal field parameters for Ln(III) ions, determined by the ab initio calculations, yielding magnetic coupling constants in the range of −1 to −5 cm–1. The wide optical transparency of 1–9 has been determined using solid state absorption spectroscopy. Samples exhibited second harmonic (SH) generation properties with SH susceptibilities ranging from 4.7 × 10–12 to 9.4 × 10–11 esu due to the presence of nonlinear optical susceptibility tensor elements (χ ijk ) χ zxx , χ zyy , χ zzz , χ zxy , χ yyz , χ yzx , χ xyz , and χ xzx , corresponding to space group P21. The determined values were also compared with the results of theoretical calculations and previous reports, indicating a potential relationship between the type of lanthanide ion and the SH intensity.
Development of nanometer-sized magnetic particles exhibiting a large coercive field (Hc) is in high demand for densification of magnetic recording. Herein, we report a single-nanosize (i.e., less ...than ten nanometers across) hard magnetic ferrite. This magnetic ferrite is composed of ε-Fe2O3, with a sufficiently high Hc value for magnetic recording systems and a remarkably high magnetic anisotropy constant of 7.7 × 10(6) erg cm(-3). For example, 8.2-nm nanoparticles have an Hc value of 5.2 kOe at room temperature. A colloidal solution of these nanoparticles possesses a light orange color due to a wide band gap of 2.9 eV (430 nm), indicating a possibility of transparent magnetic pigments. Additionally, we have observed magnetization-induced second harmonic generation (MSHG). The nonlinear optical-magnetoelectric effect of the present polar magnetic nanocrystal was quite strong. These findings have been demonstrated in a simple iron oxide, which is highly significant from the viewpoints of economic cost and mass production.
Solid refrigerants exhibiting a caloric effect upon applying external stimuli are receiving attention as one of the next-generation refrigeration technologies. Herein, we report a new inorganic ...refrigerant, rubidium cyano-bridged manganese-iron-cobalt ternary metal assembly (cyano-RbMnFeCo). Cyano-RbMnFeCo shows a reversible barocaloric effect with large reversible adiabatic temperature changes of 74 K (from 57 °C to -17 °C) at 340 MPa, and 85 K (from 88 °C to 3 °C) at 560 MPa. Such large reversible adiabatic temperature changes have yet to be reported among caloric effects in solid-solid phase transition refrigerants. The reversible refrigerant capacity is 26000 J kg
and the temperature window is 142 K. Additionally, cyano-RbMnFeCo shows barocaloric effects even at low pressures, e.g., reversible adiabatic temperature change is 21 K at 90 MPa. Furthermore, direct measurement of the temperature change using a thermocouple shows +44 K by applying pressure. The temperature increase and decrease upon pressure application and release are repeated over 100 cycles without any degradation of the performance. This material series also possesses a high thermal conductivity value of 20.4 W m
K
. The present barocaloric material may realize a high-efficiency solid refrigerant.
Iron(III) oxide shows a polymorphism, characteristic of existence of phases with the same chemical composition but distinct crystal structures and, hence, physical properties. Four crystalline phases ...of iron(III) oxide have previously been identified: α-Fe2O3 (hematite), β-Fe2O3, γ-Fe2O3 (maghemite), and ε-Fe2O3. All four iron(III) oxide phases easily undergo various phase transformations in response to heating or pressure treatment, usually forming hexagonal α-Fe2O3, which is the most thermodynamically stable Fe2O3 polymorph under ambient conditions. Here, from synchrotron X-ray diffraction experiments, we report the formation of a new iron(III) oxide polymorph that we have termed ζ-Fe2O3 and which evolved during pressure treatment of cubic β-Fe2O3 (Ia3 space group) at pressures above 30 GPa. Importantly, ζ-Fe2O3 is maintained after pressure release and represents the first monoclinic Fe2O3 polymorph (I2/a space group) that is stable at atmospheric pressure and room temperature. ζ-Fe2O3 behaves as an antiferromagnet with a Néel transition temperature of ~69 K. The complex mechanism of pressure-induced transformation of β-Fe2O3, involving also the formation of Rh2O3-II-type Fe2O3 and post-perovskite-Fe2O3 structure, is suggested and discussed with respect to a bimodal size distribution of precursor nanoparticles.
The development of multifunctional oriented polar crystals combining diverse optical, nonlinear optical, and magnetic phenomena are desirable. Two enantiomorphic assemblies YbIII(TPPO)3(NCE)3 (E = S ...(“YbS”), Se (“YbSe”); TPPO = triphenylphosphine oxide) are prepared. Both crystallites show ultralow‐frequency (ULF) Raman scattering for molecular materials with a value of 16 cm−1 (0.48 THz), originating from collective vibrations of the TPPO ligand and pseudohalides, which is supported by ab initio calculations. Moreover, YbS and YbSe crystals exhibit high‐intense second harmonic generation (SHG) phenomena along the threefold rotation c‐axis. The polarization‐variation of the pumping laser electric field experiment performed on single crystals gives a unique insight into the tensor elements constituting the R3 space group. Replacement of thiocyanide with selenocyanide in YbSe compound increases the second harmonic signal attributed to increased polarization. Besides, they also exhibit 4f‐metal centered high‐performance near‐infrared luminescence thermometric properties and weak single‐molecule magnet behaviors. They can also serve as a platform to study the magnetic and linear/nonlinear optical cross effects.
Two chiral compounds containing pseudohalides are prepared, which exhibit Raman shift in the sub‐terahertz region. They also reveal second‐harmonic generation properties in the powder and single‐crystal forms comparable to potassium dihydrogen phosphate standard. Additionally, the presence of Yb(III) ions facilitates ratiometric thermometer behavior in the near‐infrared region and reveals dynamic magnetic properties upon applied dc field.
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