Designer Diamond Anvil Cell Research Articles

Sound velocity of hexagonal close-packed iron to the Earth’s inner core pressure

Here we determine the compressional and shear wave velocities (vp and vs) of hexagonal close-packed iron, a candidate for the main constituent of the Earth’s inner core, to pressures above 300 gigapascals using a newly designed diamond anvil cell and inelastic X-ray scattering combined with X-ray diffraction. The present results reveal that the vp and vs of the Preliminary reference Earth model (PREM) inner core are 4(±2)% and 36(±17)% slower than those of the pure iron, respectively at the centre of the core. The density and sound velocity of the PREM inner core can be explained by addition of 3(±1) wt% silicon and 3(±2) wt% sulphur to iron‒5 wt% nickel alloy. Our suggested inner core composition is consistent with the existing outer core model with oxygen, as the growth of the inner core may have created a secular enrichment of the element in the outer core.

Pressure-induced superconductivity in SnSb2Te4

Here we firstly report the pressure-induced superconductivity in phase change materials SnSb2Te4. Single crystals of SnSb2Te4 were grown using a conventional melting-down method. The resistance under pressure was measured using an originally designed diamond anvil cell with boron-doped diamond electrodes. The temperature dependence of the resistance under different pressures has been measured up to 32.6 GPa. The superconducting transition of SnSb2Te4 appeared at 2.1 K () under 8.1 GPa, which was further increased with applied pressure to a maximum onset transition temperature 7.4 K under 32.6 GPa.

Magnetic transition temperatures follow crystallographic symmetry in samarium under high-pressures and low-temperatures

Magnetic ordering temperatures in rare earth metal samarium (Sm) have been studied using an ultrasensitive electrical transport measurement technique in a designer diamond anvil cell to high-pressure up to 47 GPa and low-temperature to 10 K. The two magnetic transitions at 106 K and 14 K in the α-Sm phase, attributed to antiferromagnetic ordering on hexagonal and cubic layers respectively, collapse in to one magnetic transition near 10 GPa when Sm assumes a double hexagonal close packed (dhcp) phase. On further increase in pressure above 34 GPa, the magnetic transitions split again as Sm adopts a hexagonal-hP3 structure indicating different magnetic transition temperatures for different crystallographic sites. A model for magnetic ordering for the hexagonal-hP3 phase in samarium has been proposed based on the experimental data. The magnetic transition temperatures closely follow the crystallographic symmetry during α-Sm → dhcp → fcc/dist.fcc → hP3 structure sequence at high-pressures and low-temperatures.

High-temperature superconductivity stabilized by electron-hole interband coupling in collapsed tetragonal phase ofKFe2As2under high pressure

We report a high-pressure study of simultaneous low-temperature electrical resistivity and Hall effect measurements on high quality single-crystalline KFe2As2 using designer diamond anvil cell techniques with applied pressures up to 33 GPa. In the low pressure regime, we show that the superconducting transition temperature T_c finds a maximum onset value of 7 K near 2 GPa, in contrast to previous reports that find a minimum T_c and reversal of pressure dependence at this pressure. Upon applying higher pressures, this T_c is diminished until a sudden drastic enhancement occurs coincident with a first-order structural phase transition into a collapsed tetragonal phase. The appearance of a distinct superconducting phase above 13 GPa is also accompanied by a sudden reversal of dominant charge carrier sign, from hole- to electron-like, which agrees with our band calculations predicting the emergence of an electron pocket and diminishment of hole pockets upon Fermi surface reconstruction. Our results suggest the high-temperature superconducting phase in KFe2As2 is substantially enhanced by the presence of nested electron and hole pockets, providing the key ingredient of high-T_c superconductivity in iron pnictide superconductors.

Hidden one-dimensional spin modulation in a three-dimensional metal.

Pressure can transform a transparent material into an opaque one, quench the moments in a magnet and force solids to flow like liquids. At 15 GPa, the pressure found 500 km below the earth's surface, the semiconductors silicon and germanium superconduct. Yet, at this same pressure, we show here that the magnetism in metallic GdSi remains completely robust even as it shrinks by one-seventh of its volume. Non-resonant X-ray magnetic diffraction in a specially designed diamond anvil cell, combined with band structure calculations, reveal the stability of the incommensurate spin density wave, which can be traced to a persistently nested portion of the Fermi surface that becomes increasingly one-dimensional under pressure. A cooperative interaction between nested, itinerant spins and local magnetic moments provides the organizing principle for the modulated magnetic order, salient both for its insights into the role of topology in ordered states and its potential functionality.

Magnetic ordering temperatures in rare earth metal dysprosium under ultrahigh pressures

Magnetic ordering temperatures in heavy rare earth metal dysprosium (Dy) have been studied using an ultrasensitive electrical transport measurement technique in a designer diamond anvil cell to a pressure of 69 GPa and a temperature of 10 K. Previous studies using magnetic susceptibility measurements at high pressures were able to track magnetic ordering temperature only till 7 GPa in the hexagonal close packed (hcp) phase of Dy. Our studies indicate that the magnetic ordering temperature shows an abrupt drop of 80 K at the hcp-Sm phase transition followed by a gradual decrease that continues till 17 GPa. This is followed by a rapid increase in the magnetic ordering temperatures in the double hcp phase and finally leveling off in the distorted face centered cubic phase of Dy. Our studies reaffirm that 4f-shell remains localized in Dy and there is no loss of magnetic moment or 4f-shell delocalization for pressures up to 69 GPa.

High pressure effects on the superconductivity in rare-earth-doped CaFe2As2

High pressure superconductivity in a rare-earth-doped Ca0.86Pr0.14Fe2As2 single-crystalline sample has been studied up to 12 GPa and temperatures down to 11 K using the designer diamond anvil cell under a quasi-hydrostatic pressure medium. The electrical resistance measurements were complemented by high pressure and low-temperature X-ray diffraction studies at a synchrotron source. The electrical resistance measurements show an intriguing observation of superconductivity under pressure, with Tc as high as ∼51 K at 1.9 GPa, presenting the highest Tc reported in the intermetallic class of 122 iron-based superconductors. The resistive transition observed suggests a possible existence of two superconducting phases at low pressures of 0.5 GPa: one phase starting at Tc1 ∼ 48 K and the other starts at Tc2 ∼ 16 K. The two superconducting transitions show distinct variations with increasing pressure. High pressure and low-temperature structural studies indicate that the superconducting phase is a collapsed tetragonal ThCr2Si2-type (122) crystal structure.

Momentum-resolved resonant inelastic X-ray scattering on a single crystal under high pressure

A single-crystal momentum-resolved resonant inelastic X-ray scattering (RIXS) experiment under high pressure using an originally designed diamond anvil cell (DAC) is reported. The diamond-in/diamond-out geometry was adopted with both the incident and scattered beams passing through a 1 mm-thick diamond. This enabled us to cover wide momentum space keeping the scattering angle condition near 90°. Elastic and inelastic scattering from the diamond was drastically reduced using a pinhole placed after the DAC. Measurement of the momentum-resolved RIXS spectra of Sr2.5Ca11.5Cu24O41 at the Cu K-edge was thus successful. Though the inelastic intensity becomes weaker by two orders than the ambient pressure, RIXS spectra both at the center and the edge of the Brillouin zone were obtained at 3 GPa and low-energy electronic excitations of the cuprate were found to change with pressure.

In situ electrical resistance and activation energy of solid C60 under high pressure

The in situ electrical resistance and transport activation energies of solid C60 fullerene have been measured under high pressure up to 25 GPa in the temperature range of 300–423 K by using a designed diamond anvil cell. In the experiment, four parts of boron-doped diamond films fabricated on one anvil were used as electrical measurement probes and a W—Ta thin film thermocouple which was integrated on the other diamond anvil was used to measure the temperature. The current results indicate that the measured high-pressure resistances are bigger than those reported before at the same pressure and there is no pressure-independent resistance increase before 8 GPa. From the temperature dependence of the resistivity, the C60 behaviors as a semiconductor and the activation energies of the cubic C60 fullerene are 0.49, 0.43, and 0.36 eV at 13, 15, and 19 GPa, respectively.

High Pressure Low Temperature Studies on 1-2-2 Iron-based Superconductors Using Designer Diamond Cells

ABSTRACTHigh pressure low temperature electrical resistance measurements were carried out on a series of 122 iron-based superconductors using a designer diamond anvil cell. These studies were complemented by image plate x-ray diffraction measurements under high pressures and low temperatures at beamline 16-BM-D, HPCAT, Advanced Photon Source. A common feature of the 1-2-2 iron-based materials is the observation of anomalous compressibility effects under pressure and a Tetragonal (T) to Collapsed Tetragonal (CT) phase transition under high pressures. Specific studies on antiferromagnetic spin-density-wave Ba0.5Sr0.5Fe2As2 and Ba(Fe0.9Ru0.1)2As2 samples are presented to 10 K and 41 GPa. The collapsed tetragonal phase was observed at a pressure of 14 GPa in Ba0.5Sr0.5Fe2As2 at ambient temperature. The highest superconducting transition temperature in Ba0.5Sr0.5Fe2As2 was observed to be at 32 K at a pressure of 4.7 GPa. The superconductivity was observed to be suppressed on transformation to the CT phase in 122 materials.

High pressure melting curve of tin measured using an internal resistive heating technique to 45 GPa

The high pressure melting curve of tin was measured to 45 GPa using a designer diamond anvil cell with an integrated internal resistive heating element. Melting of the tin sample was detected by an abrupt increase in the electrical resistance of the sample and also by a change in the slope of the electrical heating power versus temperature curve. The melting temperatures determined by these two methods are in good agreement with each other. We find that the melting temperature of tin tends to monotonically increase with increasing pressure and reaches a temperature of about 2000 K at 45 GPa.

Phase transformation and resistivity of dumbbell-like ZnO microcrystals under high pressure

High-pressure Raman spectra and in situ electrical resistivity measurement of the dumbbell-like ZnO microcrystals have been investigated by using the diamond-anvil-cell technique at room temperature. The dumbbell-like ZnO microcrystals were synthesized via a facile solution method under mild conditions. In terms of the Raman results, the dumbbell-like ZnO microcrystals underwent a transition from wurtzite to rock-salt structure with increasing pressure and the phase-transition pressure was about 11.13 GPa. In situ electrical resistivity measurement of the dumbbell-like ZnO microcrystals was performed on a designed diamond anvil cell. The change in electrical resistivity related to the phase structure for the ZnO microcrystals was observed with the applied pressure of up to 34.86 GPa. Moreover, the pressure dependence of the electrical resistivity for the dumbbell-like ZnO microcrystals annealed at different conditions was also investigated.

Electron Transport Property of CdTe under High Pressure andModerate Temperature by In-Situ Resistivity Measurement in Diamond AnvilCell

In situ resistivity measurement has been performed to investigate theelectron transport property of powered CdTe under high pressure andmoderate temperature in a designed diamond anvil cell. Several abnormalresistivity changes can be found at room temperature when the pressureincreases from ambient to 33 GPa. The abnormal resistivity changes atabout 3.8 GPa and 10 GPa are caused by the structural phase transitionsto the rock-salt phase and to the Cmcm phase, respectively. The otherabnormal resistivity changes at about 6.5 GPa, 15.5 GPa, 22.2 GPa andabout 30 GPa never observed before are due to the electronic phasetransitions of CdTe. The origin of the abnormal change occurred atabout 6.5 GPa is discussed. The temperature dependence of theresistivity of CdTe shows its semiconducting behaviour at least before11.3 GPa.

Phase Transition of FeS in Terms of In-Situ ResistanceMeasurement

Electrical properties of stoichiometric iron sulfide (FeS) areinvestigated under high pressure with a designed diamond anvil cell. Theprocess of phase transition is reflected by changing the electricalconductivity under high pressure, and the conductivity of FeS with theNiAs structure is found to be much smaller than other phases. Two newphase transitions without structural change are observed at 34.7 GPaand 61.3 GPa. The temperature dependence of the conductivity is foundto be similar to that of a semiconductor when the pressure is higherthan 35 GPa.

Physical and mechanical properties of C60 under high pressures and high temperatures

The physical and mechanical properties of a C60 fullerene sample have been investigated under high pressure–high temperature conditions using a designer Diamond Anvil Cell. Electrical resistance measurements show evidence of C60 cage collapse at 20 GPa, which leads to the formation of an insulating phase at higher pressure. Energy dispersive X-ray diffraction (EDXD) data indicated that the characteristic fcc reflections gradually decrease in intensity and eventually disappear above 28 GPa. A C60 sample was laser-heated at a pressure of 35 GPa to a temperature of 1910±100 K and, subsequently, decompressed to ambient conditions. The photoluminescence spectra and the Raman spectrum of the pressure–temperature-treated sample were measured at a low temperature of 80 K. Raman peak at 1322.3 cm−1 with full-width half-maximum of 2.9 cm−1 was observed from the sample, which is attributed to the hexagonal diamond phase in the sample. The room temperature photoluminescence spectra showed a symmetric emission band centered in the red spectral range with a peak at 690 nm. The structural analysis of the pressure–temperature-processed C60 sample using EDXD method showed strong internal structure orientation and a phase close to hexagonal diamond. Mechanical properties such as hardness and Young’s modulus were measured by nanoindentation technique and the values were found to be 90±7 and 1215±50 GPa, respectively and these values are characteristic of sp3-bonded carbon materials.

Physical pressure effect on the charge-ordering transition ofBaSmFe2O5.0

Pressure effects on the charge-ordering (CO) transition have been investigated in ${\mathrm{BaSmFe}}_{2}{\mathrm{O}}_{5.0}$ by means of synchrotron-radiation x-ray powder-diffraction measurement together with a specially designed diamond anvil cell. It was found that the critical temperature ${T}_{\mathrm{CO}}$ for the CO transition steeply (-56 K/GPa) decreases as pressure increases, and eventually the CO transition disappears about 2.6 GPa. Search for interrelations between the structural parameters and ${T}_{\mathrm{CO}}$ revealed that orthorhombic distortion s $[\ensuremath{\equiv}(a\ensuremath{-}b)/(a+b)],$ is the dominant structural parameter for the CO transition of ${\mathrm{BaSmFe}}_{2}{\mathrm{O}}_{5.0}.$

Spectroscopy of Charged Donors and Many-Electron Effects in Semiconductor Quantum Wells

Far infrared magnetospectroscopic studies of negative donor ions (D — ), and donors in the presence of many excess electrons in high magnetic fields in GaAs/AlGaAs quantum wells are reviewed. Both singlet and triplet transitions of well-center D -ions were observed and are in good agreement with recent theoretical calculations. For off-well-center D -ions evidence for a predicted magnetic-field-induced unbinding of the second electron was found. In the presence of many excess electrons the D --singlet and -triplet transitions are blue-shifted substantially and evolve into bound magnetoplasmon excitations. Cusps are observed at integral and fractional Landau-level filling factors (v) in a plot of normalized blue-shift of the D -singlet-like bound magnetoplasmon transition vs. v. For v < 1, the singlet-like bound magnetoplasmon transition continuously approaches the isolated D -singlet transition with increasing magnetic field, while the triplet-like transition loses strength, irrespective of the electron density. Exact diagonalization studies of a donor ion with a few electrons in a parabolic lateral confining potential show the importance of electron—electron interactions and localization due to the long-range fluctuating potential in explaining this behavior. High pressure studies in a specially designed diamond anvil cell exhibit a continuous evolution from bound magnetoplasmon transitions to isolated D -transitions to neutral donor transitions in a single sample as the pressure is increased and the electron density in the wells is decreased.