Xu-Guang Zheng

Saga University

We report on an investigation of the temperature-dependent ordering of the hydrogen/deuterium atoms in geometrically frustrated magnets Co2(OH)3Br and its deuterated Co2(OD)3Br, to shed light on the origin of the newly-identified ferroelectricity using Raman spectroscopy. Significant changes in the Raman frequencies and line-widths of the Raman-act...

Piezoelectric LiNbO3:Pr³⁺ has recently attracted attention as a so-called multi-piezo material, exhibiting simultaneously piezoluminescence and piezoelectricity. In order to investigate and improve the performance of piezoluminescence and piezoelectricity in the newly found multi-piezo material LiNbO3:Pr³⁺, a systematic study has been carried out o...

Ultrasensitive and sustainable near‐infrared (NIR)‐emitting piezoluminescence is observed from noncentrosymmetric and ferroelectric‐phase Sr3Sn2O7 doped with rare earth Nd3+ ions. Sr3Sn2O7:Nd3+ (SSN) with polar A21am structure is demonstrated to emit piezoluminescence of wavelength of 800–1500 nm at microstrain levels, which is enhanced by the ferr...

Geometrically frustrated kagome-lattice antiferromagnets have received much attention because of their exotic magnetic behaviors. Here we report the synthesis, structure, and magnetism of an S=5/2 quasiclassical new spin kagome compound. Polycrystalline compounds of MgxMn4−x(OH)6Cl2, with a nominal ideal chemical formula of MgMn3(OH)6Cl2, have been...

The temperature-dependent dynamics of the hydrogen/deuterium atoms in geometrically frustrated magnets Co2(OH)3Br and its deuterated form Co2(OD)3Br were investigated by muon spin relaxation (μSR). The deuterium atoms in Co2(OD)3Br were found to be rapidly fluctuating at high temperatures, which should be arising as a quantum atomic effect due to t...

The electronic structure of mineral tetrahedrite Cu12Sb4S13 showing a metal-semiconductor transition (MST) at TMST = 85 K has been investigated by means of Cu 1s x-ray absorption spectroscopy with the partial fluorescence yield mode (PFY-XAS) and Cu 2p-1s x-ray emission spectroscopy (XES). Remarkable changes are detected in both the PFY-XAS and XES...

Quantum spins on a triangular lattice may bring out intriguing and exotic quantum ground states. Here we report a magnetodielectric system of CuOHCl wherein S=1/2Cu2+ spins constitute a two-dimensional triangular lattice with the layers weakly coupled via Cl-H-O bonding. Despite strong magnetic interactions, as expected from the relatively high val...

Spin behaviors on kagome lattices have received increased attention because of their exotic magnetic states. Here, we report magnetic ordering in the S=2 kagome antiferromagnet MgFe3(OH)6Cl2. The compound has been synthesized by selectively replacing the magnetic ions in the triangular planes of its parent compound of deformed pyrochlore Fe2(OH)3Cl...

Red-emitting piezoluminescence (elasticoluminescence) is achieved by doping rare earth Pr(3+) into the well-known piezoelectric matrix, LiNbO3 . By precisely tuning the Li/Nb ratio in nonstoichiometric Li x NbO3 :Pr(3+) , a material that exhibits an unusually high piezoluminescence intensity, which far exceeds that of any well-known piezoelectric m...

An extensive study of hydroxyl salts Co2(OD)3Cl/Co2(OH)3Cl utilizing muon-spin-relaxation (μSR), nuclear magnetic resonance (NMR), and Raman spectroscopy, supplemented by dielectric constant and magnetic susceptibility measurements, has revealed a unique multiferroic system with deuterium-order-type ferroelectricity and geometrically frustrated mag...

The muon spin relaxation (μSR), which uses spin-polarized muons to probe tiny local field in matters, is a useful tool for studying spin-related phenomena in magnets, superconductors and semiconductors, etc. Here we report a first successful application to ferroelectrics. We utilized μSR to detect a ferroelectric transition in a newly-identified fe...

A detailed temperature-dependent Raman spectroscopic study revealed a new type of deuterium-order ferroelectrics in a geometrically frustrated magnet Co2(OD)3Cl at Tε = 229 K. Significant changes in the parameters of the Raman vibration modes were observed near Tε, suggesting a strong phonon-charge coupling. Additional asymmetric phonon bands appea...

The low temperature Raman spectroscopic (4000-95 cm–1) investigation on the hydroxyl cobalt chloride Co2(OH)3Cl and deuteroxyl cobalt chloride Co2(OD)3Cl polycrystalline samples has been performed from the room temperature down to 4 K closing to the liquid Helium temperature. Lineshapes of Raman mode Eg (about 130 cm–1 assigned to the normal symmet...

Factor group analysis on the deformed pyrochlore-structure hydroxyl transition metal halides M2(OH)3X (M = Co, Fe and Mn; X = Cl, Br and I) with the crystal symmetry R3̄m ≡ D3d5 of space group No. 166 for their infrared (IR) and Raman spectroscopic studies are, for the fist time to the best of our knowledge, reported. Through a standard factor grou...

Dielectric constants and Raman spectra of single crystal CuO were measured at temperatures between 77 and 295 K. Through dielectric measurements, we observed dielectric anomalies at the two successive magnetic transitions 230 and 213 K along the three crystal axes, which is in consistence with our previously reported dielectric-magnetic coupling. B...

S = 1/2 quantum-spin systems of the kagome lattice have received intense recent attention because they are expected to be promising candidates for novel quantum states such as spin liquid, spin nematic, and other unknown exotic states. Here we report an unusual transition in a highly two-dimensional and slightly distorted S = 1/2 quantum kagome sys...

The proton NMR spectrum of Cu2Cl(OH)3 at low temperature in zero applied field has two sharp peaks. This result means that the majority of magnetic moments order antiferromagnetically at low temperature. The magnetic structure determined by comparing the observed proton NMR spectrum with the numerical calculated ones in several magnetic models show...

Through ten years physical investigation on the geometrically frustrated coordination compound series basic (hydroxyl and deuteroxyl) transition-metal halides M2(OH/D)3X (M=Mn, Fe, Co, Ni and Cu; X=Cl, Br and I), we have determined the existence of four crystal structures, whose space groups belong to Nos. 11, 14, 62 and 166, respectively, in this...

The low temperature (T) Raman spectroscopic study on the geometrically frustrated clinoatacamite γ-Cu2(OH)3Cl is reported. By measuring the T-dependent spectral profiles and representative modes, we have obtained auxiliary evidence of successive magnetic transitions near Tc1 =18.1 K and Tc2 =6.4 K determined accurately by the magnetic experiments i...

Raman spectroscopy is a valuable and complementary tool for studying geometrically frustrated magnetic systems due to the intrinsic spin-phonon coupling. Here, we report on a Raman spectroscopic study of the geometrically frustrated spin 1/2 antiferromagnet microcrystalline clinoatacamite Cu2(OH)3Cl, focusing on the anomalous transition into the in...

Hydroxyl salts of the type M2(OH)3X, and M(OH)X, where M represents a transition metal ion and X represents a halogen ion, widely exist as minerals and were recently reported to be geometrically frustrated magnets. Here, we report the finding of ferroelectric response in them. First, we observed strong magnetic-lattice-dielectric couplings in all o...

Isolated spin tetrahedral systems with weak intertetrahedral couplings, as have been reported for Cu2Te2O5X2 (X = Cl, Br) and the related compound Cu4Te5O12Cl4, have received much attention recently because they represent an interesting class of magnets that consist of weakly coupled magnetic clusters and, in particular, they can directly demonstra...

We have measured the magnetic field dependence of the specific heat up to H=6 T in a geometrically frustrated magnet, clinoatacamite Cu2Cl(OH)3, with the corner-sharing tetrahedron structure of the Cu2+ ions. At H=0 T, the specific heat exhibits two anomalies at T1=6.2 K and at T2=18.1 K T1 shows a reentrant behavior in the T - H phase diagram, whi...

Using elastic and inelastic neutron scattering techniques with and without application of an external magnetic field H, the magnetic ground states of ZnxCo4−x(OD)6Cl2 (x=0,1) were studied. Our results show that for x=0, the ground state is a magnetic long-range ordered (LRO) state where each tetrahedron forms an “umbrella”-type structure. On the ot...

Using elastic and inelastic neutron scattering techniques with and without application of an external magnetic field $H$, the magnetic ground states of Zn$_x$Co$_{4-x}$(OD)$_6$Cl$_2$ ($x=0,1$) were studied. Our results show that for $x=0$, the ground state is a magnetic long-range ordered (LRO) state where each tetrahedron forms an "umbrella"-type...

We have examined the magnetic structure of Co2(OD)3Cl with magnetic Co^2+ (3d^7; s= 3/2) ions using neutron powder diffraction data. Magnetic structure that yields the best refinement factor is an ``umbrella''-type antiferromagnetic structure with ab-components of magnetic moments in the kagome plane forming a q=0 120^o structure and the moments ar...

Spin fluctuations and spin-liquid behaviors of frustrated kagome antiferromagnets have received intense recent attention. Although most severe frustration was predicted for an Ising kagome antiferromagnet, a real material system of undistorted kagome lattice has not been found so far. Here we report the frustrated magnetism of a new Ising kagome an...

Raman spectra of the geometrically frustrated material sample β-Co2(OH)3Cl have first, to the best of our knowledge, been measured down to liquid nitrogen temperature using the experimental conditions of 10X-objective @ 60 mW and 50X-objective @ 5 mW, respectively. It is found that most Raman bands blueshift with decreasing the sample temperature,...

Raman spectra of the magnetic geometric frustration material – the botallackite-structure α-Cu2(OH)3Cl polycrystalline sample were measured down to liquid N2 temperature. It is found that the hydroxyl stretching bands shift abnormally according to the lattice thermal expansion effect of normal materials, i.e., they redshift with decreasing the samp...

Raman (4000-95 cm–1) spectra of the recently identified magnetic geometric frustration material – deformed pyrochlore-structure hydroxyl cobalt bromide β-Co2(OH)3Br polycrystalline sample were measured using 10X and 50X microscopic objectives under different laser powers at room temperature. It is found that the obtained Raman bands at these experi...

The newly identified magnetic geometric frustration material-botallackite-structure deuteroxyl copper bromide α-Cu2(OD)3Br sample was successfully synthesized in the same single phase (polycrystalline) as the H-isotope substituted sample of α-Cu2(OH)3Br, and its IR (4000-400 cm–1) absorption and Raman (4000-95 cm–1) spectra at room temperature are...

We investigated a three-dimensional frustrated 3d-electron magnet on a pyrochlore-like lattice Ni2(OH)3Cl with s = 1 by means of 1H-NMR measurements. Previous specific heat measurements reported that this material shows a phase transition at 4.0 K and also has an anomaly at around 20 K. Our 1H-NMR measurement in 0.73 T has demonstrated that both th...

At room temperature, the mid-infrared spectra of geometrically frustrated natural atacamite (hydroxyl copper chloride, beta-Cu2(OH)3Cl) in the range of 4 000-400 cm(-1) were measured by FTIR spectrometers, and meanwhile its Raman spectrum in the range of 4 000-95 cm(-1) was obtained by Jobin Yvon LabRAM HR800 Raman spectrometer. According to its cr...

Raman vibrational spectra of the selected basic (hydroxyl OH and deuteroxyl OD) transition-metal halides, geometrically frustrated material series α-, β-, γ-Cu2(OH)3Cl, α-Cu2(OH)3Br, β-Ni2(OH)3Cl, β-Co2(OH)3Cl, β-Co2(OH)3Br, γ-Cu2(OD)3Cl, and β-Co2(OD)3Cl are measured at room temperature and analysed to investigate the relationship between the micr...

Vibrational spectra (Raman 4000-95 cm-1 and mid-IR 4000-400 cm-1) of the atacamite-structure Ni2(OH)3Cl, including a rarely reported kind of asymmetric trimetric hydrogen bond, as a member of the geometrically frustrated material series and its deuteride Ni2(OD)3Cl are, to the best of our knowledge, reported for the first time and analyzed at room...

Mid-infrared absorption and Raman spectra of the geometrically frustrated material series, hydroxyl cobalt halides ß-Co2(OH)3Cl and ß-Co2(OH)3Br, are first, to the best of our knowledge, measured at room temperature, to study the corresponding relationship between their vibrational spectral properties and crystal microstructures. Through the compar...

Mid-infrared (4000–400 cm−1) absorption and Raman (4000–95 cm−1) spectra of the series of geometrically frustrated materials, botallackite-structure basic copper halides, α-Cu2(OH)3Cl and α-Cu2(OH)3Br polycrystalline samples were first, to the best of our knowledge, measured, respectively, to study the corresponding relationship between their vibra...

Three types of FTIR spectrometers were employed to measure the mid-infrared (4000-400 cm-1) absorption spectra of geometrically frustrated hydroxyl cobalt chloride Co2(OH)3Cl, and the intrinsic absorption peaks in the functional group region and fingerprint region were selected and assigned to corresponding vibrational modes according to its known...

The proton NMR spectrum of Mn2Cl(OH)3 with zero applied field has rather sharp peaks, and a glassy property is not observed. The temperature dependence of NMR frequency shows that antiferromagnetic transition occurs at TN1 (=3.4 K), and that no anomaly appears at TN2 (=2.7 K). However, the change in frequency is considerably larger than the normal...

The mid-infrared absorption spectra of geometrically frustrated hydroxyl cobalt halogenides Co2(OH)3Cl and Co2(OH)3Br are measured by FTIR spectrometers, and the stretching vibrational modes of hydroxyl groups are found to be 3549cm−1 and 3524cm−1 respectively. Through finding their true terminal O-H group stretching vibration frequencies, we obtai...

Structure and magnetic properties of the rhombohedral-structure compound Co2(OH)3Br, a member of the geometrically frustrated series of the compounds M2(OH)3X where the magnetic ions form a deformed pyrochlore lattice, were studied using dc and ac magnetic susceptibilities, heat-capacity, neutron powder-diffraction, and muon-spin-rotation/-relaxati...

The geometrically frustrated material-deuteroxyl cobalt chlorides Co2(OD)3Cl sample was first, to the best of our knowledge, successfully synthesized in the same single phase as the famous Co2(OH)3Cl, and their mid-infrared absorption spectra (4000-400cm–1) and Raman spectra (4000-95 cm–1) are first, to the best of our knowledge, measured respectiv...

Basic copper chloride Cu-2(OH)(3)Cl and Cu-2(OD)(3)Cl polycrystalline sample were successfully synthesized in the same single phase of clinoatacamite-structure, and the latter's mid-infrared absorption spectra (4000-400cm(-1)) and Raman spectra (4000-95cm(-1)) were first, to the best of our knowledge, measured respectively by FTIR spectroscopy and...

The mid-IR and Raman spectra of geometrically frustrated atacamite hydroxyl copper chloride are measured by FTIR spectroscopy and HR800 Raman spectroscopy, respectively. The microscopic origins of bands within the functional group and the Fingerprint regions are suggested by the known crystal structure parameters. Five distinct regions involved in...

We present a systematic investigation of the crystal and electronic structures and the magnetic properties above and below the metal-insulator transition of ball-milled VO2 nanoparticles and VO2 microparticles. For this research, we performed a Rietveld analysis of synchrotron radiation x-ray diffraction data, OK x-ray absorption spectroscopy, VL3...

Magnetism of the rhombohedral structure Fe2(OH)3Cl [β-Fe2(OH)3Cl], a member of the geometric frustration series M2(OH)3X where the magnetic ions form a deformed pyrochlore lattice, was studied using dc and ac susceptibilities, heat-capacity, neutron powder-diffraction, and muon spin relaxation (μSR) measurements. Antiferromagnetic transition was ob...

A bulk-sensitive measurement is required in order to observe changes in the electronic states across metal-insulator transition (MIT). We have measured unoccupied and occupied electronic states for V2O3 powder above and below the MIT by O K partial fluorescence yield (PFY) and soft x-ray emission spectroscopy (SXES) using a soft x-ray emission spec...

When the thin film of ZnS:Mn nanoparticles deposited on a glass substrate is elastically deformed by applying a load, then initially the mechanoluminescence (ML) intensity increases with time, attains a peak value Im at a particular time tm, and later on it decreases with time. The rise and decay characteristics of the ML produced during release of...

We have performed the specific heat study in a new geometrically frustrated system, clinoatacamite Cu2Cl(OH)3 with the corner-sharing tetrahedron structure of the Cu2+ ions with 5=1/2 Heisenberg spin. At H=0 T, two anomalies are observed at T2=18.1 K and at T2=6.2 K. The specific heat decreases rapidly below T2 and shows no anomaly down to T=150 mK...

The deformed pyrochlore lattice compound clinoatacamite, Cu2(OH)3Cl, shows intriguing frustrated magnetism and 1/4 substitution of Cu with nonmagnetic Zn leads to the two-dimensional kagome lattice ZnCu3Cl2(OH)6 that exhibits spin liquid behaviour. These findings renewed interest in botallackite Cu2(OH)3Cl, which is a polymorphous structure of clin...

As a part of an extensive study of the new geometric frustration series M2(OH)3X (M: 3d magnetic ion; X: halogen ion) on deformed pyrochlore lattice we have investigated in detail the magnetism of Co2(OH)3Cl1−xBrx, in which the magnetic state was found to be very sensitive to the anion substitution. Co2(OH)3Br was found to undergo antiferromagnetic...

As a part of an extensive study on the new geometric frustration series M2(OH)3X on deformed pyrochlore lattice, we have found an exotic antiferromagnetic order in atacamite-structure Ni2(OH)3Cl. Strong frustration exists in Ni2(OH)3Cl with antiferromagnetic transition below TN=4 K. While neutron diffraction witnessed unambiguously a long-range ord...

Magnetic interactions in a new geometrically frustrated system (Co1−xFex)2(OH)3Cl are investigated using magnetic susceptibility and μSR study. While Co2(OH)3Cl is ferromagnetic and Fe2(OH)3Cl antiferromagnetic, the partially substituted series (Co1−xFex)2(OH)3Cl show spin-glass behaviours, wherein ferromagnetic interactions prevail for low Fe conc...

Following the discovery of frustrated magnetism in deformed pyrochlore lattice Cu2(OH)3Cl and Co2(OH)3Cl we have extensively investigated the material series in the chemical formula of M2(OH)3X, with M = Cu, Co, Ni, Fe, Mn, and X = Cl, Br, or I. In atacamite-structure Ni2(OH)3Cl, strong geometric frustration and an exotic antiferromagnetic transiti...

1H NMR measurements of 3d electron three-dimensional frustrated systems, Co2(OH)3Cl with s = 3/2 and Cu2(OH)3Cl with s = 1/2 have been performed. The relaxation rates T-11 of both compounds suggest the development of spin correlations at much higher temperatures compared with the magnetic transition temperatures. The temperature dependence of T-11...

Most solids expand when they are heated, but a property known as negative thermal expansion has been observed in a number of materials, including the oxide ZrW2O8 (ref. 1) and the framework material ZnxCd1-x(CN)2 (refs 2,3). This unusual behaviour can be understood in terms of low-energy phonons, while the colossal values of both positive and negat...

Recently, we observed a kagome-ice-like partial ferromagnetic order with coexisting fluctuation in a deformed pyrochlore structure Co2(OH)3Cl. Here, we show that when lattice defects are present, the remaining fluctuating spins in this material further freeze at lower temperatures below T<Tg=4 K after it initially freezes into the partial ferromagn...

NMR studies of a geometrically frustrated system, Co2Cl(OH)3, are carried out at low temperature. The NMR results of 59Co and 1H nuclei show that long-range ordered ferromagnetic moments on the triangular lattice plane coexist microscopically with disordered moments on the kagome lattice plane. The moment direction is not ordered. Although the diso...

The complex permittivity of lightly doped Bi2Sr2YCu2O8+delta was measured in order to investigate the carrier dynamics near the insulator-to-metal transition. By suppressing the extrinsic polarization due to some contact effects, we found a rapid rise in the c-axis dielectric constant εc\prime with increasing temperature at TM˜ 225 K. Below TM, the...

A systematic study of magnetic susceptibility measurements is carried out on distorted tetrahedral lattice hydroxyhalides Fe 2 (OH) 3 Cl, Mn 2 (OH) 3 Cl, Mn 2 (OH) 3 Br, and Co 2 (OH) 3 Br, following our recent finding of coexisting antiferromagnetic order and disorder in Cu 2 (OH) 3 Cl (clinoatacamite). These transition metal hydroxyhalides are fo...

Recently, we observed the co-existence of a long-range magnetic order and spin fluctuation in a clean compound of clinoatacamite, Cu2(OH)3Cl (PRL95 (2005) 057201). The present work reports magnetic studies on other compounds of this transition metal series M2(OH)3Cl, where M represents three-dimensional (3D)-electron magnetic ions of Co2+, Fe2+, et...

Order or disorder often exists in a uniform spin system consisting of one kind of magnetic ion. Nevertheless, they rarely coexist in normal conditions. Our thermodynamic and microscopic magnetic studies of Co2(OH)3Cl, a distorted tetrahedral lattice compound with uniform Co2+ spin, demonstrate that the spins located on one corner of the tetrahedron...

Colloidal suspensions of copper oxide (CuO) nanoparticles were prepared by an alcothermal method, in which copper acetate was reacted with sodium hydroxide in the presence of acetic acid in ethanol at 78°C. The prepared suspension was stable for up to 1 month without stabilizers such as surfactants. Transmission electron microscopy analyses reveale...

The thermal expansion has been measured on the single crystalline CuO under pressure up to 1.3 GPa. Two anomalies in the temperature dependence of thermal expansion were observed at antiferromagnetic transition temperatures, TN1=230 K and TN2=212 K, at ambient pressure, suggesting a strong magnetoelastic coupling in CuO. TN2 is found to decrease wi...

Muon spin relaxation/rotation (μSR) are carried out on a new magnetic system of M2X(OH)3 (M=transition metal, X=halogen), which we show to be a new geometric frustration system for d-electron spins. Contrasting behaviors were observed for clinoatacamite Cu2Cl(OH)3 and Co2Cl(OH)3. Clinoatacamite Cu2Cl(OH)3 undergoes antiferromagnetic transition at T...

Muon spin rotation experiments are carried out on clinoatacamite, Cu2Cl(OH)3, which is a new geometrically frustrated system featuring a three-dimensional network of corner-sharing tetrahedral 3d Cu2+ spins. A long-range antiferromagnetic order occurs below 18.1 K with a surprisingly small entropy release of about 0.05Rln2/Cu. Below 6.5 K, the stat...

Muon spin relaxation/rotation (µSR) and magnetic susceptibility measurements were carried out on antiferromagnetic nanoparticles of CuO. Nanoparticles with center size of around 5 nm were prepared by ball-milling from single crystals of CuO and investigated using µSR measurements. In the ~5 nm assembly, the TN was reduced drastically to ~30 K, comp...

The filled skutterudite compound Pr0.87Fe4Sb12 was prepared in single-crystal form and characterized via x-ray-diffraction, neutron-diffraction, specific-heat, electrical-resistivity, and magnetization measurements. Long-range magnetic ordering occurs at Tc&ap;4.1K , with the bulk magnetization described by the critical exponents beta=0.57,gamma=0....

The high electrostrictive strain, strong mechanoluminescence, and electroluminescence obtained in the [(1-x)BaTiO3-xCaTiO 3]:Pr ceramics near the solubility limit on the side of the composite were analyzed. It was found that in the diphasic region, the interactions between the large ionic polarization in Ba0.1Ca0.9TiO 3:Pr with the domains in Ba0.7...

A systematic study on pure-phase samples of the polymorphous natural cuprates Cu2Cl(OH)3, atacamite and botallackite, is carried out using synchrotron x-ray-diffraction, magnetic susceptibility, and muon spin rotation/relaxation (μSR) measurements. Atacamite and botallackite are found to undergo antiferromagnetic transition at TN=9.0 and TN=7.2 K,...

Unconventional magnetic properties are found for a quantum spin system of mineral clinoatacamite, Cu2Cl(OH)3. Clinoatacamite is found to undergo an antiferromagnetic transition at 18.1 K with a small entropy fall (0.05R ln 2). At temperatures below 6.4 K, it transits into a disordered spin-glass-like state but with large specific heat anomalies. Th...

Crystalline ZnS films were prepared on glass substrates from a high-crystallinity ZnS pellet using an ion-plating method. The crystallinity and friction-induced photon-emitting capability (triboluminescence) of the films were greatly enhanced by postannealing under vacuum. The annealing treatment made the ZnS films strongly adherent to the glass su...

Magnetic susceptibility and muon spectroscopy measurements are carried out on antiferromagnetic nanoparticles (AFN) of CuO that are directly prepared by ball-milling a single crystal. The recently reported ferromagnetic features in AFN CuO of sol–gel growth are confirmed. New and significant result of the present work is a direct observation of an...

Recently, we have found a new phenomenon, named elasticoluminescence, in which intensive visible light can be emitted by the application of mechanical stress in the elastic deformation region. This phenomenon, contrary to piezoelectricity, can sense changes in mechanical stress without any electrical contacts or electrodes. Elastico-deformation lum...

The room temperature sensing of ozone by transparent p-type semiconductor CuAlO2 was discussed. A transparent p-type semiconductor, CUAlO 2, shows selective and reversible response to ozone gas at room temperature. This materials potential could be exploited using a combination of the p-type transparent CuAlO2 with an existing n-type ozone sensing...

The natural cuprate botallackite, Cu2Cl(OH)3, is found to be a new antiferromagnet with Magnetic susceptibility properties under strong field show non-linear M–H properties indicating metamagnetism. The TN and the super-exchange coupling are discussed and compared with its polymorph atacamite and other copper oxides on the basis of their structural...

Elastico-deformation luminescence in strontium aluminates was investigated systematically using precisely controlled pure-phase Eu-doped strontium aluminates of SrAl ₁₂ O ₁₉, Sr ₄ Al ₁₄ O ₂₅, SrAl ₄ O ₇, α- SrAl ₂ O ₄, β- SrAl ₂ O <sub>4</s...

The magnetic property of natural cuprate Cu2Cl(OH)3 is of interest in view of the interaction between the 3d Cu2+–Cu2+ spins that can be compared with the coupling in high-Tc cuprates. A magnetic susceptibility study on mineral crystal atacamite Cu2Cl(OH)3 shows that the atacamite is an intrinsic antiferromagnet with A metamagnetism is also reveale...

A high level of hole doping in CuO is realized by Li-substitution and pronounced effect on the structural, transport and magnetic properties of the cupric oxide is reported. The antiferromagnetic transition is reduced from TN=229K in the undoped CuO to TN=91K in Cu0.84Li0.16O and the activation energy for the transport conduction decreases in an or...

High-resolution powder x-ray-diffraction measurements on cupric oxide CuO are carried out in an extensive temperature range from 100 K to 1000 K. Anomalies in the lattice constants appear at the known antiferromagnetic phase transitions at TN1=230K and TN2=213K, respectively, suggesting strong spin-lattice coupling in CuO. The Rietveld analysis wit...