Mn Single Crystals Research Articles

High piezoelectric sensitivity and related parameters of a novel lead-free 1–0–3 composite

ABSTRACTA piezoelectric performance of a novel 1–0–3 composite based on lead-free single crystals with 4mm symmetry is first analysed. Ferroelectric domain-engineered alkali niobate-tantalate based single crystals provide large values of the piezoelectric coefficients g*3j and g*h, squared figures of merit d*33 g*33 and d*h g*h, and a 0–3 matrix promotes a large piezoelectric anisotropy in specific volume-fraction ranges. An aspect-ratio effect concerned with spheroidal inclusions of a piezoelectric Li2B4O7 single crystal in a polymer medium is studied to show the considerable influence of these inclusions on the effective parameters of the composite. Values of g*33∼ 103 mV·m / N, g*h∼ (102–103) mV·m / N, d*33 g*33∼ 10−10 Pa−1, and d*h g*h∼ (10−11–10−10) Pa−1, and the large anisotropy of the piezoelectric coefficients d*3j and electromechanical coupling factors k*3j are achieved in the 1–0–3 composite based on a [001]-poled [Lix(K1-yNay)1-x](Nb1-zTaz)O3:Mn single crystal and make this composite suitable for piezoelectric sensor, energy-harvesting and hydroacoustic applications.

High frequency transducer for vessel imaging based on lead-free Mn-doped (K0.44Na0.56)NbO3 single crystal

We report a high frequency ultrasonic transducer up to 50 MHz for vessel imaging based on a lead-free (K0.44Na0.56)NbO3–0.5 mol. % Mn (Mn-KNN) single crystal, which has a high electromechanical coupling coefficient kt of 0.64 and a large thickness frequency constant Nt of 3210 kHz · mm. The Krimholtz, Leedom, and Mattaei (KLM) equivalent circuit model was utilized to simulate and optimize the pulse-echo response combined with PiezoCAD software. Theoretically, a high -6 dB bandwidth of 74.94% was obtained at a center frequency of 50.47 MHz and optimized matching conditions. The experimental results showed a center frequency of 51.8 MHz with a −6 dB bandwidth of 70.2%. The excellent global performance makes this lead-free single-crystal transducer quite potential in an environmentally friendly vessel imaging transducer.

A single-mode Mn-doped 0.27PIN-0.46PMN-0.27PT single-crystal ultrasonic motor

Mn-modified rhombohedral phase yPb(In1/2Nb1/2)O3-(1-x-y)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PIN-PMN-PT:Mn) single crystal has attracted considerable attention for its outstanding piezoelectric properties and high mechanical quality factor. Here, we report a device innovation using Mn doped 0.27PIN-0.46PMN-0.27PT single crystal in a single-mode piezoelectric ultrasonic motor. Based on the analyses of actuator characteristics with finite element method, the PIN-PMN-PT:Mn crystal actuator predicts lower excitation frequency, lower driving voltage, and less power loss comparing with the PZT ceramic actuator. A prototype motor (size: 12 × 6 × 1.5 mm3) was fabricated and tested. The typical output of this PIN-PMN-PT:Mn motor is a speed up to 42.3 cm/s, a driving torque of 0.42 N cm, and an output power density of 0.45 W/cm3, under the driving voltage of 21 V0−P. This work presents that PIN-PMN-PT:Mn single crystal is quite advantageous in making miniaturized and high-power piezoelectric ultrasonic motors.

Investigation on growth and characteristics of undoped and Mn doped glycinium oxalate single crystals

This work aims at investigating the undoped Glycinium Oxalate (GO) and Manganese doped Glycinium Oxalate (Mn:GO) single crystals that were prepared via slow evaporation method. The single crystals grown were characterized for its structural, vibrational, optical, topographical, electrical and mechanical properties. Single and Powder X-ray diffraction suggests that the grown crystals are crystallized in the monoclinic structure. The functional groups and the effect of moisture on the undoped and doped GO crystals can be analyzed with the help of FTIR spectrum. The undoped and doped GO single crystal shows low absorption in the entire visible and IR region, which is suitable for optical device applications. The emission of green light with the use of Nd:YAG laser (λ = 1064 nm) confirmed the second harmonic generation properties of the grown crystals. Dielectric measurements were carried to the wide range of frequency (50 Hz–5 MHz) at different temperatures. The determined Vickers hardness number and work hardening coefficient of the grown crystals ascertains the soft nature of the crystal.

Paramagnetic resonance of LaGaO3: Mn single crystals grown by floating zone melting

The EPR spectrum of Mn-doped lanthanum gallate single crystals grown by floating zone melting with optical heating has been studied. In contrast to the crystals grown according to the Czochralski method, no manganese is found in these crystals even after high-temperature annealing in air. The spectral characteristics of Fe3+ and Gd3+ centers in crystals prepared by various methods have been compared in the rhombohedral phase, and the fourth-rank nondiagonal parameters of the Fe3+ trigonal centers have been determined, as well.

TEM and SEM analyses of the orientation relations of recrystallized grains in a stable Al–1 wt.%Mn single crystal

The recrystallization grain orientations developed during annealing of a deformed single crystal have been characterized by in-situ TEM and ex-situ SEM. Single crystal samples of Al–1wt.%Mn alloy of brass(110) [1-1-2] orientation were deformed in a channel-die to develop 2 sets of intersecting microbands at strains of 0.51 and 0.92 and then lightly annealed. Local orientation measurements demonstrate a strong relation between the deformed orientations and the limited number of recrystallized grain orientation groups. The misorientation angles across the recrystallization front were grouped in the range 25–55° (with a maximum near 40–45°) around axes located near three normals of the 4 {111} planes; the [1-11] rotation axis parallel to the transverse direction was not found. Two groups of rotation axes were identified: (i) rotation axes very close to the <111> or <112> directions, and (ii) a scattered sequence between <111>–<112>, <111>–<122> or <122>–<012> directions. The orientations of new grains that nucleate during thin foil heating in TEM were compared with those formed during static recrystallization of bulk samples analysed by SEM/EBSD, both in the centre section of electropolished samples and in near-surface areas of abraded samples. In all experiments the new grain orientations belong to the same groups and the distribution of misorientation axes across the recrystallization front was similar.

Luminescence properties of CaF2:Mn optically transparent ceramic

The optically transparent ceramics (OTCs) of CaF2:Mn were fabricated by a vacuum hot-press method. Photo-luminescence (PL) and radio-luminescence measurements were carried out on CaF2:Mn OTCs to study the effect of processing on the luminescence properties of the material. The temperature dependence of PL and decay kinetics was investigated down to 77K. The results were compared with the reported luminescence properties of CaF2:Mn single crystals. The comparison shows that the luminescence is similar at room temperature; however, the evolution of luminescence with temperature and decay mechanism of Mn2+ centers in OTCs is quite different. A possible explanation for the differences in the luminescence properties of CaF2:Mn OTC has been proposed.

Possible unconventional superconductivity in substituted BaFe2As2 revealed by magnetic pair-breaking studies.

The possible existence of a sign-changing gap symmetry in BaFe2As2-derived superconductors (SC) has been an exciting topic of research in the last few years. To further investigate this subject we combine Electron Spin Resonance (ESR) and pressure-dependent transport measurements to investigate magnetic pair-breaking effects on BaFe1.9M0.1As2 (M = Mn, Co, Cu, and Ni) single crystals. An ESR signal, indicative of the presence of localized magnetic moments, is observed only for M = Cu and Mn compounds, which display very low SC transition temperature (Tc) and no SC, respectively. From the ESR analysis assuming the absence of bottleneck effects, the microscopic parameters are extracted to show that this reduction of Tc cannot be accounted by the Abrikosov-Gorkov pair-breaking expression for a sign-preserving gap function. Our results reveal an unconventional spin- and pressure-dependent pair-breaking effect and impose strong constraints on the pairing symmetry of these materials.

Vibrational states of a water molecule in a nano-cavity of beryl crystal lattice.

Low-energy excitations of a single water molecule are studied when confined within a nano-size cavity formed by the ionic crystal lattice. Optical spectra are measured of manganese doped beryl single crystal Mn:Be3Al2Si6O18, that contains water molecules individually isolated in 0.51 nm diameter voids within the crystal lattice. Two types of orientation are distinguished: water-I molecules have their dipole moments aligned perpendicular to the c axis and dipole moments of water-II molecules are parallel to the c-axis. The optical conductivity σ(ν) and permittivity ɛ'(ν) spectra are recorded in terahertz and infrared ranges, at frequencies from several wavenumbers up to ν = 7000 cm(-1), at temperatures 5-300 K and for two polarizations, when the electric vector E of the radiation is parallel and perpendicular to the c-axis. Comparative experiments on as-grown and on dehydrated samples allow to identify the spectra of σ(ν) and ɛ'(ν) caused exclusively by water molecules. In the infrared range, well-known internal modes ν1, ν2, and ν3 of the H2O molecule are observed for both polarizations, indicating the presence of water-I and water-II molecules in the crystal. Spectra recorded below 1000 cm(-1) reveal a rich set of highly anisotropic features in the low-energy response of H2O molecule in a crystalline nano-cavity. While for E∥c only two absorption peaks are detected, at ~90 cm(-1) and ~160 cm(-1), several absorption bands are discovered for E⊥c, each consisting of narrower resonances. The bands are assigned to librational (400-500 cm(-1)) and translational (150-200 cm(-1)) vibrations of water-I molecule that is weakly coupled to the nano-cavity "walls." A model is presented that explains the "fine structure" of the bands by a splitting of the energy levels due to quantum tunneling between the minima in a six-well potential relief felt by a molecule within the cavity.

The transition from dynamics to statics in the electron-spin-resonance spectra of impurity Mn2+ ions in strontium titanate

The electron-spin-resonance (ESR) spectra of SrTiO3:Mn single crystals have been investigated. Results unambiguously indicate that the impurity center formed by an Mn2+ ion has a dynamic nature. In the high temperature range (T > 100 K), ESR spectra of Mn2+ ions reveal cubic symmetry; the spectrum is found to broaden significantly with a decrease in temperature. Upon cooling to T < 10 K, low-symmetry centers of Mn2+ ions with a strong orientational dependence emerge in the spectra. Temperature evolution of the ESR spectrum can be described within the model of a dynamic off-center Mn2+ ion substituting for the Sr2+ ion, with a transition to the static regime at low temperatures with an average localization energy of ∼2.4 ± 0.4 meV for Mn2+ centers due to random deformations.

Evaluation Of kinetic parameters Of Li2b4o7:Mn single crystal

The kinetic parameters of a newly developed Li2B4O7:Mn single crystal phosphor have been presented. Li2B4O7 single crystal doped with Mn were grown via the Czochralski method. Thermoluminescence (TL) glow curve of Li2B4O7:Mn single crystal exhibits two well separated TL peaks at about 363 and 478K, later being more intense, with a heating rate of 1K/s. The high-temperature glow curve at 478K is important for dosimetric studies of Li2B4O7 (LBO) doped with Mn. The kinetic parameters (activation energy (E), frequency factor (s) and kinetic order (b)) of the main glow peak (478K) have been calculated using initial rise (IR), isothermal decay (ID) and peak shape (PS) methods. Activation energies obtained by IR, ID and PS were found to be 1.24, 1.18 and 1.20eV, respectively. Similarly, the frequency factors were determined using isothermal decay and peak shape methods and found as 7.85×1011 and 3.27×1011s−1, respectively. All results obtained using these methods are compared and discussed.

Synthesis, Thermal and Magnetic Properties of New Coordination Compounds based on Mn(NCS)2 with 2‐Chloropyrazine and 2‐Methylpyrazine as neutral Co‐Ligand

AbstractReaction of manganese(II) thiocyanate with 2‐chloropyrazine leads always to the formation of a compound of composition Mn(NCS)2(2‐chloropyrazine)4 (1‐Mn/Cl) that consists of discrete complexes, in which the manganese cation is coordinated by two terminal thiocyanato anions and four 2‐chloropyrazine ligands. In contrast, with 2‐methylpyrazine only an aqua complex of composition Mn(NCS)2(2‐methylpyrazine)2(H2O)2 (1‐Mn/CH3) is obtained that also consists of discrete octahedrally coordinated complexes. Moreover, a few single crystals of Mn(NCS)2(2‐chloropyrazine)4·Mn(NCS)2(2‐chloropyrazine)2(H2O)2·2‐chloropyrazine trisolvate (2‐Mn/Cl) and Mn(NCS)2(2‐methylpyrazine)2(H2O)2·Mn(NCS)2(H2O)4 (2‐Mn/CH3) were accidently obtained but no larger amounts are available. On heating, 1‐Mn/Cl and 1‐Mn/CH3 transforms into new compounds of composition Mn(NCS)2(L)2 (L = 2‐chloropyrazine) (4‐Mn/Cl) and 2‐methylpyrazine (3‐Mn/CH3). Surprisingly on further heating 1‐Mn/CH3 looses additional 2‐methylpyrazine ligands and transforms into a new compound of composition Mn(NCS)2(2‐methylpyrazine) (4‐Mn/CH3). Compound 4‐Mn/Cl is isotypic to its cobalt(II) analog and 4‐Mn/CH3 is isotypic to Cd(NCS)2(2‐methylpyrazine) reported recently and therefore, both structures were refined by the Rietveld method. The crystal structures of both compounds are strongly related. They consists of dimeric units, in which each two manganese cations are linked by pairs of μ‐1, 3‐bridging thiocyanato anions, which are further connected into layers by single μ‐1, 3‐bridging anionic ligands. In contrast to 4‐Mn/Cl, in 4‐Mn/CH3 these layers are further linked into a 3D coordination network by the 2‐methylpyrazine ligands. Magnetic measurements reveal that 1‐Mn/Cl, 1‐Mn/CH3, and 3‐Mn/CH3 shows only Curie‐ or Curie‐Weiss paramagnetism, whereas 4‐Mn/Cl and 4‐Mn/CH3 shows antiferromagnetic ordering at TN = 22.9 K and at 26.5 K. The results of these investigations are compared with those obtained for related compounds.

Orientation dependence of piezoelectric properties and mechanical quality factors of 0.27Pb(In1/2Nb1/2)O3-0.46Pb(Mg1/3Nb2/3)O3-0.27PbTiO3:Mn single crystals

The complete set of material constants of single domain rhombohedral phase 0.27Pb(In1/2Nb1/2)O3-0.46Pb(Mg1/3Nb2/3)O3-0.27PbTiO3:Mn single crystal has been determined. The orientation dependence of piezoelectric, dielectric, and electromechanical properties was calculated based on these single domain data. The maximum piezoelectric and electromechanical properties were found to exist near the [001]C pseudo-cubic direction. In addition, the piezoelectric properties of [001]C poled crystals with “4R” multi-domain configuration were experimentally measured and compared with the calculated values. Only a small difference (3%) was found between experimental and theoretical values, indicating the high piezoelectric properties in the “4R” state are mainly from intrinsic contributions. The mechanical quality factors Q33 are significantly improved by the Mn-doping for the “4R” domain engineered crystals but almost no change for the single domain “1R” state. On the other hand, Q15 of both single domain and multidomain crystals were found to increase with Mn-doping, due to the internal bias induced by acceptor dopants, which clamps the domain wall motions and restricts polarization rotation.

Complete set of elastic, dielectric, and piezoelectric constants of [011]C poled rhombohedral Pb(In0.5Nb0.5)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3:Mn single crystals.

Mn modified rhombohedral Pb(In0.5Nb0.5)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT:Mn) single crystals poled along [011]C crystallographic direction exhibit a "2R" engineered domain configuration, with macroscopic mm2 symmetry. The complete sets of material constants were determined using combined resonance and ultrasonic methods, and compared to [001]C poled PIN-PMN-PT:Mn crystals. The thickness shear piezoelectric coefficient d15 and electromechanical coupling factor k15 were found to be on the order of ∼3000 pC/N and 0.92, respectively, with longitudinal piezoelectric coefficient d33 and coupling factor k33 being on the order of ∼1050 pC/N and 0.90. Of particular importance is that PIN-PMN-PT:Mn single crystals exhibited high mechanical quality factor Q33 ∼ 1000, comparable to "hard" PZT8 ceramics, which can also be confirmed by the low extrinsic contribution, being ≤2% from the Rayleigh analysis.

Electron Paramagnetic Resonance Characterization of Mn2+Ion in GaAs:Mn Crystal

The electron paramagnetic resonance (EPR) of a new Mn 2+ center in a GaAs:Mn single crystal has been investigated with an X-band spectrometer at 3.8 K. The spectroscopic splitting parameters g i j and the zero-field splitting parameters B k q were fully determined using the effective spin Hamiltonian. The local site symmetry of the Mn 2+ ion turns out to be monoclinic from the rotation patterns together with the spectroscopic splitting parameters and the zero field splitting parameters. The new Mn 2+ center with monoclinic site symmetry is believed to originate from interstitial Mn 2+ ions. The energy levels of the ground state for the Mn 2+ impurity ion embedded in a GaAs crystal, are calculated as a function of applied magnetic field.

Crystallinity Control of Ferromagnetic Contacts in Stressed Nanowire Templates and the Magnetic Domain Anisotropy

We report the controlled growth of single-crystalline ferromagnetic contacts through solid state reaction at nanoscale. Single-crystal Mn(5)Si(3) and Fe(5)Ge(3) contacts were grown within stressed Si and Ge nanowire templates, where oxide-shells were used to exert compressive stress on the silicide or germanide. Compared to polycrystalline silicide and germanide structures observed within bare nanowires, the built-in high strain in the oxide-shelled nanostructures alters the nucleation behavior of the ferromagnetic materials, leading to single crystal growth in the transverse/radial direction. Interestingly, the compressive stress is also found to affect the magnetic anisotropy of the ferromagnetic contacts. In-plane and out-of-plane magnetization were observed in Fe(5)Ge(3) for different crystal orientations, showing distinctly preferred domain orientations. These interesting results display the capability to control both the crystallinity and the magnetic anisotropy of ferromagnetic contacts in engineered nanostructures.

Growth and characterization of air annealing Mn-doped YAG:Ce single crystal for LED

The growth of Mn-doped YAG:Ce (yttrium aluminum garnet doped cerium) single crystal by the Czochralski (CZ) method and the characterization of its spectroscopy and color-electric parameters are presented. The absorption spectra indicate that the crystal absorbed highly in the 300–500nm wavelength range. The emission spectrum of the crystal consists of a peak around 538nm when excited by 460nm blue light, which prove the YAG:Ce,Mn single crystal could be used in the white light emitting doides (LED). The different charges of Mn ions have different luminescence properties, and the air annealing process for the single crystal would change the concentration of Mn ions with different charges, which could influence the emission intensity of the single crystal.

Hydrothermal synthesis, silver decoration and electrochemistry of LiMPO4 (M = Fe, Mn, and Co) single crystals

Ionothermal synthesis was recently reported as a very attractive method to design new electrode materials for lithium ion batteries. Here, we report the use of hydrothermal synthesis, using water or a water-ionic liquid (IL) mixture as reacting medium, to prepare hexagonal shaped micrometric LiMPO4 (M=Fe, Mn and Co) single crystals oriented along the b direction at 260°C. The influence of the reacting medium and the reaction time on the size of single crystals has been ascertained with the feasibility of growing after one month reacting time 700μm LiFePO4 single crystals in water-IL media and smaller ones (80–120μm) in water. The latter exhibit electrochemical capacities of 145mAh/g at C/2 rate with excellent capacity retention when cycled at 100°C. Last, we show a novel way to decorate the surface of “LiFePO4” crystals through the reduction of silver nitrate into metallic silver. This enables an easy determination of the crystal growth directions while providing insights in the lithium diffusion processes.

Contrasting effects of magnetic ions on the superconductivity in Tl0.4K0.4Fe2−y−xMxSe2 (M = Mn and Ni)

The transport and magnetic properties together with the superconductivity of Tl0.4K0.4Fe2−y−xMxSe2 (M = Mn and Ni) single crystals are studied. On the transport side, both Mn doping and Ni doping lead to a decrease of charge carrier density. However, contrasting effects on superconductivity are found, i.e. substitution of Fe by Ni results in a drastic depression of the onset superconducting transition temperature (Tonsetc), while the Tonsetc value remains nearly unchanged in Mn-doped samples. A remarkable ferromagnetic interaction is found in Ni-doped samples but is absent in Mn-doped samples. The present results suggest that the magnetic pair-breaking effect alone cannot explain the different behavior of depression of superconductivity in Mn-doped and Ni-doped samples. The occurrence of ferromagnetic interaction is responsible for the rapid decrease of Tonsetc in Ni-doped samples.

Resonant photoemission at the L3 absorption edge of Mn and Ti and the electronic structure of 1T-Mn0.2TiSe2

Resonant valence band x-ray photoelectron spectra (ResPES) excited near the 2p3/2 core level energies, 2p x-ray photoelectron spectra (XPS) and L3,2 x-ray absorption spectra (XAS) of Ti and Mn in single crystals of 1T-Mn0.2TiSe2 were studied for the first time. The ionic–covalent character of the bonds formed by the Mn atoms with the neighboring Se atoms in the octahedral coordination is established. From the XPS and XAS measurements compared with the results of atomic multiplet calculations of Ti and Mn L3,2 XAS, it is found that the Ti atoms are in the ionic state of 4 + and the Mn atoms are in the state of 2 + . In ResPES of Mn0.2TiSe2 excited near the Ti 2p3/2 and Mn 2p3/2 absorption edges the Ti 3d and Mn 3d bands at binding energies just below the Fermi level are observed. According to theoretical calculations of E(k) the Ti 3d states are localized in the vicinity of the Γ point and the Mn 3d states are localized along the direction K–Γ–M in the Brillouin zone of the crystal.