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Ferromagnetic Zn1-xCuxO (ZnO:Cu) films were epitaxially grown on n-GaN(0001)/Al2O3(0001) by radio-frequency magnetron sputtering at a substrate temperature as low as 700°C. X-ray diffraction θ-2θ scans, -scans, and surface morphology studies revealed the degree of crystallinity, epitaxiality, and grain size. The full-width at half-maximum of the peak for the ZnO:Cu films deposited on GaN was below 0.18° according to ω-scans. The chemical bonding states and depth profiles of the films were investigated by X-ray photoelectron spectroscopy (XPS) and with a glow discharge spectrometer (GDS). A magnetic property measurement revealed that Cu-doped ZnO films exhibit ferromagnetic behavior with a strong exchange interaction between sp-band carriers and localized d electrons at room temperature.

Epitaxially twinned (0 2 8)-oriented Bi 3.25 La 0.75 Ti 3 O 12 (BLT) thin films were grown on GaN(0 0 2)/Al 2 O 3 (0 0 0 6) substrates by pulsed laser deposition. The BLT layer deposited on GaN substrate showed sixfold-like symmetric peaks in a φ scan of (0 0 6) reflection and 12 peaks in that of the (1 1 7) reflection. In order to investigate hetero-epitaxial growth, origin of six and 12 peaks in the φ scan, and the domain structure of the BLT thin film, the X-ray analysis including θ – 2 θ , ω , φ scan, and pole figure measurement were performed. The hetero-epitaxial growth was studied by atomic arrangements and domain distribution with calculated lattice mismatch, interplanar angles, and atomic distances.

We report on a study of magnetic cluster in Co-doped ZnO using neutron diffraction. The samples are fabricated by the sol-gel process and the structural properties are characterized by X-ray diffraction and neutron diffraction. The diffraction data obtained by neutron are compared with the results of X-ray diffraction and refined by the Rietveld refinement method. The secondary phases are detected by neutron diffraction in above 5 mol% Co-doping of ZnO samples and the fractions of the phases in the samples are calculated. In particular, the Co metal phase is clearly observed in 30 mol% Co-doped ZnO. However, these secondary phases are not detected by X-ray diffraction due to reasons such as X-ray absorption by Co K-edge and incoherent X-ray scattering. We discuss the advantage of using neutron diffraction in studying the secondary phase and suggest the solubility limit of Co-doping.

We have used liquid-delivery metal-organic chemical vapor deposition (LD-MOCVD) to grow polycrystalline CoxTi1-xO2 anatase films on SiO2/Si substrates. A scanning Auger microscope (SAM) technique is introduced to obtain the elemental mapping images from the Co-doped TiO2 film. The existence of Co-rich complex oxide compound was identified from an elemental distribution of the annealed film. The magnetic distribution of the film was investigated using a magnetic force microscope (MFM). The co-existence of Co-metal states with Co-oxide compounds at the surface region of the film were investigated by narrow-scans of X-ray photoelectron spectroscopy (XPS).

133Cs (I=7/2) nuclear magnetic resonance in a Cs2CuCl4 single crystal grown by using the slow evaporation method was measured in its three mutually perpendicular crystal planes. The 133Cs resonances of two different groups with two crystallographically inequivalent cesium nuclei, Cs(I) and Cs(II), in the unit cell were recorded. The transferred hyperfine fields for Cs(I) and Cs(II) calculated from the paramagnetic shift and the molecular susceptibility measurements could be expressed by the linear equation Hhf=AT+B. The angular dependence of the 133Cs nuclear magnetic resonance spectra showed that the Cs(I) and the Cs(II) nuclei had different values for the quadrupole coupling constant. The electric field gradient tensors of Cs(I) and Cs(II) were symmetric, and the orientations of their principal axes did not coincide. The Cs(I) ion surrounded by 11 chlorine ions had a small quadrupole parameter, a smaller charge distribution, and a small value for the transferred hyperfine field. However, the Cs(II) ion surrounded by nine chlorine ions had a larger quadrupole parameter, a larger charge distribution, and a larger value for the transferred hyperfine field.

The spin?lattice relaxation processes of the 39K and 27Al nuclei in KAl(SO4)2?12H2O crystals were studied; we found that these processes can be described by linear combinations of two and three exponential functions, respectively. From these results, we conclude that the discontinuity in the curve of the spin?lattice relaxation rate near Tc (= 360?K) corresponds to the first-order phase transition of the crystal. In the case of the 39K nucleus, the relaxation rate increases as the temperature increases. The relaxation rate of the 27Al nucleus decreases below Tc as the temperature increase, while above Tc its relaxation rate increases with increasing temperature. The temperature dependences of these spin?lattice relaxation rates can be described with the power law . Least square fits of the relaxation rates at temperatures below Tc indicate that k = 2 for the 39K nucleus and k = 7 for the 27Al nucleus. From these results, we conclude that the 39K and 27Al spin?lattice relaxations occur from Raman relaxation processes.

The ferromagnetism of ZnO-based magnetic semiconductors has been investigated by theoretical calculation and many kinds of experiments. In the Cu-doped ZnO system, ferromagnetic ordering by Cu magnetic moments does not exist, but Cu-doped ZnO can have ferromagnetism due to the distortion of the ZnO-based structure by Cu doping. In this study, we investigated the magnetic properties of Cu-doped ZnO and discussed the possible origin of magnetism in this system. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The measurement of P-E loops, dielectric, thermo-mechanical and micro-structural properties was performed on ferroelectric Bi4 − x La x Ti3O12 (BLT) crystals in order to clarify their ferroelectricity and to provide an explanation for the phase transition with La incorporated. The grown c-axis Bi4.3Ti3O12 and Bi3.65La0.47Ti3O12 crystals showed ferroelectricity but the P-E hysteresis loop of the c-axis Bi2.76La1.67Ti3O12 crystal was not fully saturated. BLT crystals tend to change from a monoclinic to an orthorhombic structure with increasing La concentration because they substitute La for Bi with a lone-pair electron. From the measurement of physical properties under varying temperatures, the ferroelectric phase transition of BLT crystals was showed to occur at temperature close to 500°C.

Cerium-modified Bi4Ti3O12 thin films were deposited on GaN substrates by the pulsed laser deposition method. The substrate temperature was varied from 600°C to 750°C in 50°C steps. The surface topographies and orientations of the Bi0.4Ce0.6Ti3O12 (BCeT) films were gradually changed in proportion to the substrate temperature. The diffusion reaction between BCeT and the GaN layer and the depth profiles of the films were investigated by Auger electron spectroscopy (AES). The ferroelectric properties and leakage current characteristics of the metal-ferroelectric-GaN stacked thin films were measured and discussed.

Temperature EPR studies of Mn2 +-doped LiCsSO4 have been reported. The coexistence of resonance lines ascribed to the para- and ferro-phase has been found in the vicinity of the second order phase transition.

Pb(Zr0.52Ti0.48)O3 thin films were fabricated on Pt/Ti/SiO2/Si substrates by the sol-gel method. A UV-photolysis process was added before the final annealing of the coated films. This UV-photolysis process made it possible to lower the crystallization temperature and to stabilize the film surface and interface during the annealing process. The UV-photolysis-processed PZT thin films exhibited enhanced ferroelectricity and a lower leakage current density than the non-treated ones. It is thought that the UV-treatment process is a very effective in enhancing ferroelectric and electrical properties for the ferroelectric random access memory device applications.

The Pb(Zr0.52Ti0.48)O3 thin films were fabricated by sol-gel method. A modified pyrolysis method, such as UV-photolysis process, was adapted before final annealing of the films. The UV-photolysis processed PZT thin films exhibited enhanced ferroelectricity (P r ) and lower leakage current density than not-treated one. UV-photolysis process also made it possible to lower the crystallization temperature and to stabilize film surface and interface. The interface states were characterized by Auger electron spectroscopy (AES). The fatigue and retention test were also examined. It is thought that the UV-treatment process is very effective to enhance ferroelectric and electrical properties for ferroelectric random access memory device applications.

The rotation patterns of the 133Cs (I=7/2) nuclear magnetic resonance (NMR) in a Cs2ZnCl4 single crystal grown by using the slow evaporation method were measured in two mutually perpendicular crystal planes. Two different groups of Cs resonances were recorded; this result points to the existence of two types of crystallographically inequivalent Cs(I) and Cs(II). The angular dependences of the NMR spectra led to different values for the quadrupole coupling constants and asymmetry parameters: e2qQ/h=148 kHz and η=0.11 for the Cs(I) ion, and e2qQ/h=274 kHz and η=0.66 for the Cs(II) ion. The EFG tensors of Cs(I) and Cs(II) are asymmetric, and the orientations of the principal axes of the EFG tensors do not coincide. Only, the principal Y-axes of the EFG tensors coincide for the Cs(I) and Cs(II) sites. The Cs(I) ion is surrounded by 11 chlorine ions, making it rather free and high in symmetry. The Cs(II) ion has only nine neighbors and seems to be more tight than the Cs(I) ion.

The proton NMR line width and spin-lattice relaxation times for LiNH 4 SO 4 single crystal were studied at low temperature range of 6 and 280 K. The changes in the proton relaxation behavior near the phase transition temperature indicates a change in the state of internal motion at the transition. The molecular motions obtained by the spin-lattice relaxation processes were found to be determined by molecular reorientation of the NH 4 ions in phases III, IV, and V. We also confirmed that the phase transitions occur at 26 and 133 K.

The low temperature phase of the ferroelastic LiCsSO 4 (LCS) crystal was investigated by the thermomechanical methods and the observation of the domains using the polarizing microscope. The thermal...

We investigated the ferroelastic domain switching due to external stress in RbMnCl 3 single crystals grown by the Czochralski method. The temperature dependence of the stress–strain hysteresis was measured. From this result, it was determined that the RbMnCl 3 single crystal undergoes a ferroelastic phase transition near T c =272 K. Also, the ferroelastic domain switching stress by the saturation effect was obtained as about 0.5 MPa; this crystal easily transforms to single-domain under the influence of slight external stress. In other words, when an external stress of 0.5 MPa is applied to RbMnCl 3 crystals there is a transformation from the twin-domain state to the single-domain state.

RbMnCl3 and CsMnCl3 order antiferromagnetically at Neel temperatures TN=94.6 K and TN=67 K, respectively. The 87Rb and 133Cs spin-lattice relaxation times in these crystals were measured in the temperature range of 270–60 K. The large change in the relaxation rate that is observed near TN indicates that the magnetic phase in these crystals undergoes a paramagnetic to antiferromagnetic transition. In both crystals, the temperature dependencies of the relaxation rates for T TN are in accordance with a single-phonon process.

The 7Li and 39K NMR relaxations in a LiKSO4 single crystal grown by the slow evaporation method were investigated by employing a pulse NMR spectrometer. From the experimental data, the quadrupole coupling constant and asymmetry parameter were determined at the temperatures of 180 and 300 K. The relaxation processes of 7Li and 39K were studied for the LiKSO4 crystal, and the relaxation times for the 7Li and 39K nuclei exhibit remarkable changes near Tc2 (=190 K). The activation energies for 7Li and 39K were determined in phases I and III. The large change in the activation energy at 190 K indicates that the Li and K ions are significantly affected during this transition. The correlation time of the 7Li calculated from the spin-lattice relaxation time and quadrupole parameters was larger than that of the 39K calculated using the same method. The reason for this is that the Li ion undergoes molecular motion as in the LiO4 groups.

Magnetic susceptibility and paramagnetic shift for central transition of 133 Cs NMR in the single crystal CsCuCl 3 which has transition temperature T N =10.5 K have been measured in the temperature range of 4.2–300 K. From experimental result, we have obtained the transferred hyperfine interaction due to the transfer of spin density from the Cu 2+ ion to the Cs + ion in CsCuCl 3 single crystal. The transferred hyperfine interaction can be expressed by the linear equation H hf =[3.54 T+2.84] (Oe) in the temperature range of 50–300 K; the H hf increases with increasing temperature. 133 Cs spin-lattice relaxation time of 133 Cs NMR in the CsCuCl 3 single crystal was also measured in the same temperature range. The temperature dependence of 1/ T 1 is nearly constant in the paramagnetic phase, while relaxation rate near T N exhibits remarkable change, indicating a drastic alternation of spin dynamics at the Neel temperature.

Effects of hydrogen plasma treatment on the electrical properties of a sol-gel-derived polycrystalline zinc oxide (ZnO) system have been studied by employing the impedance spectroscopy. The complex impedance data were analyzed by employing the equivalent circuits. Hydrogen plasma treatment markedly increased the low-frequency range of the constant values of the real part of the complex impedance. As a result of the plasma treatment, the electrical conductivity was found to increase by about two orders of magnitude, with the activation energy being reduced from 0.62 eV to 0.30 eV. The dielectric constant also showed a two-fold increase following the plasma treatment.

We report on the simultaneous realization of p-type conductivity and strong ferromagnetism in heavily Co-doped ZnO thin films in the presence of a high concentration of hydrogen impurities. Through ab initio calculations, we find that the microscopic origin of hole carrier generations and ferromagnetic ordering is due to the partially occupied band of the percolative structures wherein the carrier-induced magnetic interactions can stabilize the strong spin-parallel state.

Hydrogen-treated ZnCoO shows magnetic behavior, which is related to the formation of Co-H-Co complexes. However, it is not well known how the complexes are connected to each other and with what directional behavior they are ordered. In this point of view, ZnCoO nanowire is an ideal system for the study of the magnetic anisotropy. ZnCoO nanowire was fabricated by trioctylamine solution method under different ambient gases. We found that the oxidation of trioctylamine plays an essential role on the synthesis of high-quality ZnCoO nanowires. The hydrogen injection to ZnCoO nanowires induced ferromagnetism with larger magnetization than ZnCoO powders, while becoming paramagnetic after vacuum heat treatment. Strong ferromagnetism of nanowires can be explained by the percolation of Co-H-Co complexes along the c-axis.

Resistivity is an intrinsic feature that specifies the electrical properties of a material and depends on electron-phonon scattering near room temperature. Reducing the resistivity of a metal to its potentially lowest value requires eliminating grain boundaries and impurities, but to date few studies have focused on reducing the intrinsic resistivity of a pure metal itself. We could reduce the intrinsic resistivity of single-crystal Ag, which has an almost perfect structure, by impurity doping it with Cu. This paper presents our results: resistivity was reduced to 1.35 mu Omega.cm at room temperature after 3 mol% Cu-doping of single-crystal Ag. Various mechanisms were examined in an attempt to explain the abnormal behavior.

Copper (Cu) thin films have been widely used as electrodes and interconnection wires in integrated electronic circuits, and more recently as substrates for the synthesis of graphene. However, the ultra-high vacuum processes required for high-quality Cu film fabrication, such as molecular beam epitaxy (MBE), restricts mass production with low cost. In this work, we demonstrated high-quality Cu thin films using a single-crystal Cu target and radio-frequency (RF) sputtering technique; the resulting film quality was comparable to that produced using MBE, even under unfavorable conditions for pure Cu film growth. The Cu thin film was epitaxially grown on an Al2O3 (sapphire) (0001) substrate, and had high crystalline orientation along the (111) direction. Despite the 10(-3) Pa vacuum conditions, the resulting thin film was oxygen free due to the high chemical stability of the sputtered specimen from a single-crystal target; moreover, the deposited film had >5 x higher adhesion force than that produced using a polycrystalline target. This fabrication method enabled Cu films to be obtained using a simple, manufacturing-friendly process on a large-area substrate, making our findings relevant for industrial applications.

By the group-theoretical method, the permissible domain walls for all 94 ferroelastic species were analyzed. This method is not only consistent with wall equations using Sapriel's strain tensor method, but also provides additional information such as the types of wall, the point groups of each domain, and the configurations of twin structures. The permisible domain walls for a given domain pair were characterized by one or more symmetry elements which are defined as the set of wall characterizing elements (WCE). We found that the Sapriel's W wall was characterized by mirror plane or two or more symmetry elements, while the W ′ wall by only one rotational symmetry element. With the help of the crystallographic consideration, the group-theoretical analysis showed that all permissible domain walls are crystallographically prominent planes with fixed indices. They are represented by W m , W b , W f , or combinations of them, depending on the WCE. Most notably, the existence of a four-fold wall, W f , is sugge...

The temperature dependence of the 133Cs nuclear magnetic resonance (NMR) in a ferroelastic CsPbCl3 single crystal has been investigated using a FT NMR spectrometer. The rotation patterns of the 133Cs NMR spectra were obtained in three mutually perpendicular planes under an applied magnetic field of 9.4 T. Two sets of seven-line structures were obtained instead of a simple seven-line structure of the 133Cs(I= 7 2 ) nucleus in CsPbCl3 crystal. From these results, the NMR parameters were obtained. These showed the same magnitudes of quadrupole coupling constants and asymmetry parameters for resonance lines of the two sets, but with different orientations. It is known that two different orientations in phases II–IV occurred in ferroelastic domains. The domain wall makes an angle of 45° with respect to the [1 0 0] axis in phases II–IV. At the transition point of 47°C, one signal from the 133Cs resonance line indicates that a phase transition takes place to a new phase with higher symmetry than tetragonal. There is no EFG tensor at the Cs site in phase I. The parameters obtained from the 133Cs NMR spectra were based on the occurrence of first-order phase transitions at 37°C and 47°C, and a second-order phase transition at 42°C.

The 1 H and 39 K spin-lattice relaxation times in a KHCO 3 single crystal grown by the slow evaporation method were investigated by employing a NMR spectrometer. The relaxation processes of 1 H and 39 K were described by a single exponential function. The large change in the relaxation time at 318 K indicates that the H and K ions are significantly affected during this transition. We know that the phase I to phase II transition is a first-order phase transition. Experimental results show that the temperature dependences of the spin-lattice relaxation time behavior were quite similar for both nuclei. From these results the activation energies for the 1 H and 39 K nuclei were obtained and the values are similar for both nuclei in phases I and II. The temperature dependences of the spin-lattice relaxation rates of 39 K are proportional to T 4 and T 7 with Raman process dominated by the phonon mechanism below T c and above T c , respectively.

We studied the temperature dependence of the stress-strain hysteresis in [N(CH 3 ) 4 ] 2 CuCl 4 and [N(CH 3 ) 4 ] 2 ZnCl 4 single crystals grown by the slow evaporation method. From the obtained re...

87Rb 1/2↔−1/2 spin-lattice relaxation time in the Rb2ZnCl4 single crystal was measured in the temperature range of 4.2–300 K. The dominant relaxation of this crystal in the whole temperature range investigated here is due to quadrupolar interaction. The changes in the 87Rb spin-lattice relaxation rate near 75 and 192 K correspond to the phase transitions in the crystal. These suggest that the phase IV to III transition is of second-order, and the phase III to II transition is of first-order. The temperature dependence of the relaxation rates in phases II, III, and IV is in accordance with the Raman process dominated by the phonon mechanism.

The 7 Li and 39 K nuclear magnetic resonances in a LiKSO 4 single crystal grown by the slow evaporation method were investigated by employing an NMR spectrometer. From the experimental data, the quadrupole coupling constant and asymmetry parameter were determined at room temperature. The principal axes corresponding to the largest principal value of the 7 Li and 39 K EFG tensors were parallel to the hexagonal c -axis. This direction was determined to be the Z -axis of the EFG tensor. The EFG tensor of 7 Li and 39 K was found to be non-axially symmetric; the lithium ion is surrounded by oxygen atoms located at a slightly distorted tetrahedron, and the resultant coordinating potassium ion was enclosed by the oxygen atoms located at nine distorted tetrahedra.

By the crystallographic consideration, all permissible domain walls were obtained for CsPbCl 3 , a crystal that undergoes very complicated phase transition sequences. We constructed the possible domain structures and classified the domain walls into various types according to the domain structures. In particular, those by a fourfold wall, W f , which was found by considering the wall symmetry were constructed. The results also showed that the W' walls, which were defined in a continuous model of the mechanical properties, are the crystallographic planes with fixed indices.

The temperature dependences of 7Li nuclear magnetic resonance in LiXSO4 (X = K, Rb, Cs, and NH4) single crystals grown by the slow evaporation method have been investigated by employing a Bruker FT NMR spectrometer. From the experimental data, the nuclear quadrupole constant, the asymmetry parameter and the principal axes of the EFG tensor were determined, and the results were compared with the crystal structure. The temperature dependences of the quadrupole parameters were explained with a single torsional mode of the Li-O bond by the Bayer theory. All the LiO4 tetrahedra in four different crystals showed torsional motion about the X-axis of the EFG tensor. Based on these results, the differences in atomic weight of X in the LiXSO4 single crystals are responsible for the differences in the torsional angular frequencies.

The 7 Li and 39 K nuclear magnetic resonances in an LiKSO 4 single crystal grown by the slow evaporation method have been investigated using a Bruker FT nuclear magnetic resonance (NMR) spectrometer. From the experimental data, the quadrapole coupling constant and asymmetry parameter were determined at room temperature and low temperature, respectively. Unlike the case at 300 K, the 7 Li NMR line consists of three sets at 180 K, while 39 K nucleus exhibits six sets for the rotation around the three crystallographic axes. The three resonance lines of 7 Li and 39 K at low temperature can be explained by the existence of three kinds of twin domain, rotated with respect to each other by 120° around the c -axis. The three resonance lines are also related to the crystallographic mirror plane. Structure of ferroelastic LiKSO 4 crystals at 180 K can be directly inferred from the domain pattern obtained by 7 Li and 39 K NMR. The above results show that the equations of the twin boundaries belong to the mm 2 F 6 mm ferroelastic species. Therefore, the symmetry of phases III and II is given by orthorhombic structure with Cmc 2 1 ( mm 2) and hexagonal structural with P 6 3 mc (6 mm ), respectively.

The proton NMR line width and spin–lattice relaxation times for [N(CH3)4]2ZnCl4 single crystal were studied over a wide temperature range. Proton spin–lattice relaxation time measurements on [N(CH3)4]2ZnCl4 yielded a minimum, which were attributed to the effect of molecular tumbling. It seems obvious that the high-temperature minima of T1 is attributable to the tumbling motion of [N(CH3)4] ions, and that the T1 below 161 K is attributable to the same molecular motion which dominates at 210 K. Then, the T1 below 161 K undergoes a slow motion. The activation energies in phase VI and IV were determined to be 13.94 and 22.49 kJ/mol, respectively.

The proton NMR line width and spin–lattice relaxation rate in a [N(CH3)4]2CuCl4 single crystal have been investigated in the temperature range of 140–340 K. A large discontinuity in the curve of the spin–lattice relaxation rate shows near 200 K: this curve corresponds to a new phase transition. The activation energies were determined at each phase from the spin–lattice relaxation times. The large change in the activation energy at 200 K indicates that the N(CH3)4 groups are significantly affected during this transition.

The temperature dependence of 7Li and 133Cs spin–lattice relaxation times in the LiCsSO4 single crystal has been investigated in the temperature range of 140–400 K. The discontinuity in the curve of the spin–lattice relaxation rate near 200 K corresponds to the phase transition in the crystal. Despite the contrasting temperature dependences of the quadrupole parameter, the spin–lattice relaxation behaviors were quite similar for both nuclei, and were dominated by the phonon mechanism. The temperature dependence of the relaxation rate is in accordance with the Raman process of the nuclear spin–lattice relaxation of T7 for Tc>T and T2 for Tc

The dependence of the dielectric constants on the applied sinusoidal mechanical field for Pb3(PO4)2 was investigated near the transition temperature. 180°C. In the ferroelastic phase, the dielectric constant showed periodic change depending on the applied stress, which is caused only by the ferroelastic domain switching. The increase and decrease of the dielectric constants under the tensional and compressive stress are attributed to the orientation change of domain under the stress. At the maximum and the minimum stress, the dielectric constants show no more sharp increase and decrease, because near these stresses possible domains were already switched to another orientation state. The dielectric change of the ferroelastic compounds under the sinusoidal stress is defined as a ferroelastic piezo-displacement.

The temperature dependence of the 7Li nuclear magnetic resonance in a LiNH4SO4 single crystal grown by the slow evaporation method has been investigated by employing a FT NMR spectrometer. The rotation patterns of the 7Li NMR spectra were obtained in three mutually perpendicular planes under an applied magnetic field of 4.7 T. The 7Li NMR spectra demonstrates the occurrence of the first-order phase transition at TC (=285 K). Two different groups of Li resonances were recorded below TC. The two groups represent the transition of 7Li NMR lines due to Li(I) and Li(II), respectively; the two signals are associated with two physically inequivalent positions of lithium atoms in the unit cell. The principal axes of the EFG tensor below TC are not the same as those above TC. The temperature dependence of e2qQ/h and η in the temperature range of 170–400 K is explained with a single torsional frequency of the Li–O ion by means of the simple Bayer theory.

The behavior of the ferroelastic DCs in [N(CH3)4]2CuCl4 was investigated by the measurement of the strain-stress hysteresis loop and of the bias stress field dependence of DC interaction potential. The ferroelastic double hysteresis loop observed in [N(CH3)4]2CuCl4 suggested the existence of the regularly spaced ferroelastic DCs in the incommensurate phase. The oscillating behavior of the second derivative of the DC interaction energy U(x) was investigated to discuss the energy minimized positions of the ferroelastic DCs.

We report on the systematic changes of surface wettability in one of the most promising transparent conducting oxide materials, Al-doped ZnO (AZO) thin films. It was revealed that the characteristic surface wettability, which would make a key role in adhesion with other layers of optoelectronic device, can be largely changed by Al concentrations and film growth temperature. Keeping the electrical conductivity constant, the water contact angle (WCA) of a 2 mol% AZO film was changed by about 50 ∘ C depending on the surface roughness. In the samples grown at 300 ∘ C, the roughness enhancement was large and a hydrophobic surface formed, whereas in the samples grown at 500 ∘ C a hydrophilic surface formed. We attributed the variation in surface wettability with growth temperature to changes in surface morphology. This result suggests that 2 mol% Al doping concentration can be considered as a critical concentration in changing of surface morphology of AZO as well as in electrical properties.

Temperature dependence of the 133Cs nuclear magnetic resonance in an LiCsSO4 single crystal grown by the slow evaporation method has been investigated by employing an FT NMR spectrometer. From the experimental data, the quadrupole coupling constant, asymmetry parameter and direction of the EFG tensor were determined in the temperature range from 180 K to 400 K. The 133Cs NMR spectra shows a phase transition at 200 K which is connected with the formation of three kinds of ferroelastic domain. The obtained results are explained by the existence of these three domains, rotated with respect to each other by 60° around the c-axis. The nuclear quadrupole coupling constant and asymmetry parameter obtained as functions of temperature for 133Cs in an LiCsSO4 single crystal are described by the linear equations and , respectively, in the temperature range 180-400 K.

The temperature dependence of 7 Li spin-lattice relaxation time in a LiNH 4 SO 4 single crystal has been investigated at 155.51 MHz in the temperature range of 210 to 340 K. The time T 1 is relatively long in the whole temperature range, and increases with temperature from 121 s at 210 K to 646 s at 340 K. The discontinuity in the curve of the spin-lattice relaxation time near 285 K corresponds to the phase transition in the crystal. This confirms that the phase-III-to phase-II-transition is a first-order phase transition. The activation energies in phases III and II are 10.93 and 3.68 kJ/mol, respectively. The large change of activation energy for phases III and II at 285 K indicates that the LiO 4 groups are significantly affected during this transition.

The coupling between an electric field and mechanical stress was investigated, focusing on the incommensurate (IC) phase of K2ZnCl4 with the ferroelectric commensurate (C) phase. The coupling by both external fields is derived theoretically by the Landau theory. In order to prove the theoretical results, the electric field dependence of dielectric constants was studied under the mechanical stress of 0 Mpa, 1.5 MPa and 2.5 MPa. Under the stress of 2.5 Mpa, the electric field dependence of X shows the anomalous behavior from the IC phase, and it corresponds to the phase transition from the IC phase to the pseudo-C phase. Such a behavior suggests the coupling between the polarization and the strain in the IC phase.

The temperature dependence of the nuclear magnetic resonance in an single crystal grown by the slow evaporation method has been investigated by employing an FT NMR spectrometer. The rotation patterns of the NMR spectra were obtained in three mutually perpendicular planes under an applied magnetic field of 4.7 T. The NMR spectra demonstrate the occurrence of the second-order phase transition at 200 K which is connected with a lowering of the site symmetry. Two kinds of ferroelastic domain below 200 K were measured. In the temperature range of 140-380 K, the nuclear quadrupole coupling constants and asymmetry parameters of in decrease as the temperature increases. The temperature dependence of and is satisfactorily explained with a single torsional frequency of the Li-O ion by simple Bayer theory.

The heat capacity of the K 2 ZnCl 4 single crystal was measured between 330 K and 415 K using an adiabatic calorimeter. A distinct anomaly of the commensurate-incommensurate transition was observed at 403.64 ±0.05 K for the first time by the adiabatic calorimetry, where the enthalpy change is Δ H = 9.990 J ·mol -1 and the entropy change is Δ S = 0.025 J · K -1 ·mol -1 . The anomaly of the heat capacity is demonstrated by the behavior of the phase soliton or the domain wall near the transition point. The heat capacity was simulated numerically by using the phenomenological Landau theory and compared with the experimental results. The anomaly of the thermal expansion near T C measured by TMA is related with a structural phase transition accompanied by the entropy change. We discuss the influence of the anomalous change of the thermal expansion compared with the heat capacity near T C .

We studied the ferroelastic domain switching due to stress in CsPbCl 3 single crystals grown by the Czochralski method. The ferroelastic domain switching stress due to a saturation effect is about 0.6 MPa. The temperature dependence of the stress–strain hysteresis was also studied. From this result, it was determined that the CsPbCl 3 single crystal undergoes a phase transition near T C1 =47°C. In other words, the phase transition due to an external mechanical stress applied to CsPbCl 3 crystals causes a transformation from one phase to another. Also, the shape of the stress–strain curve in phases IV, III, and II are different from that of phase I. It was confirmed by the stress–strain hysteresis that CsPbCl 3 crystals have ferroelastic characteristics in phases IV, III, and II.

We investigated ferroelastic domain switching due to stress in single crystals grown by a slow evaporation method. The ferroelastic domain switching stress due to the saturation effect is about 0.9 MPa. The temperature dependence of the stress-strain hysteresis was also studied. From this result, it was determined that the single crystal undergoes a phase transition near K. In other words, the phase transition due to an external mechanical stress applied to crystals causes a transformation from the ferroelastic to the paraelastic phase. From these results, it was confirmed that crystals have ferroelastic characteristics below .

GaMnAs and Be-codoped GaMnAs films grown via molecular beam epitaxy (MBE) were heat treated and the stability of Mn in the matrix was investigated. MnAs had a stable phase at the low growth temperature, but MnGa was stable at the annealing temperature. Be-codoping did not prevent the precipitation processes, but Be itself was stable during the annealing process to maintain the GaAs matrix at the high conductivity.

GaMnN and Be-codoped GaMnN were grown via molecular beam epitaxy using a single GaN precursor and their structural and magnetic properties were examined. X-ray diffraction and superconducting quantum interference device (SQUID) measurements revealed that the grown layers are homogeneous without precipitates. The saturation magnetization of GaMnN has increased from ∼4 to ∼16 emu/cm3 via codoping of Be. The d–d exchange interaction between Mn atoms was discussed for the ferromagnetism of GaMnN.