Search

In this paper, we demonstrate a novel strategy to introduce Fe into a Bi 2 Se 3 system through growth of crystals with nominal composition (FeSe) x Bi 2 Se 3. For x < 0.04 , Fe is shown to act mostly as a non-magnetic impurity; it uniformly enters the lattice and monotonically increases the c -lattice parameter, electronic doping level, and Shubnikov–de Haas mobility. The most striking observation is the record high Hall mobility of 8600 cm 2 /V s at 4.2 K for the smallest FeSe content (x = 0.002) that further decreases with x. Elevated mobility is accompanied by a high residual resistance ratio and a rather moderate shift of Shubnikov–de Haas oscillations to a smaller field. These findings indicate that Fe admixture cures the point defects in Bi 2 Se 3 and, thus, opens an effective way to suppress the defect subsystem in Bi 2 Se 3 -based topological insulator materials. [ABSTRACT FROM AUTHOR]

The CsPbBr3 single crystal detector emerges as a highly promising candidate among semiconductor nuclear radiation detectors, which exhibits an extensive potential application across a multitude of critical domains, particularly in nuclear physics, nuclear energy, nuclear medicine, etc. However, the polarization problem has limited the application and development of CsPbBr3 detectors and has even posed a significant hindrance to their practical implementation. In this paper, a pre-designed SnO2/CsPbBr3 hetero-junction was meticulously engineered at the interface of the Ti/CsPbBr3/Ti detector, aiming to solve the polarization problem. This paper investigates the effects of the SnO2/CsPbBr3 hetero-junction on the electrical characteristics, detection performance, and long-term stability of the detector. The final results demonstrated that the SnO2/CsPbBr3 hetero-junction had multiple beneficial effects on the CsPbBr3 detector. On the one hand, the SnO2/CsPbBr3 hetero-junction exhibited superior electron extraction efficiency when compared to the Ti/CsPbBr3 interface. On the other hand, the SnO2 layer played a crucial role in preventing the migration of ions from the CsPbBr3 crystal to the interface, as well as in blocking the permeation of atmospheric and moisture elements from the detector surface to the interface. Consequently, the SnO2/CsPbBr3 hetero-junction detector exhibited superior detection performance and enhanced long-stability when compared to the Ti/CsPbBr3/Ti detector. After the interface enhancement, the SnO2/CsPbBr3 hetero-junction detector achieved an improved energy resolution of 13.59% at an electric field of 6000 V/cm and maintained a stable energy resolution of approximately 24 ± 5% at 3000 V/cm for over 12 h. The study of the SnO2/CsPbBr3 hetero-junction detector in this work provided a new perspective for enhancing the detection performance and ensuring the long-term stability of CsPbBr3-based detectors. [ABSTRACT FROM AUTHOR]

Zinc single crystals have been shocked by planar impact along the [ 10 1 ¯ 0 ] axis as well as in the off-axis direction. The evolution of compression waves has been analyzed from the free surface velocity profiles of zinc single crystal samples. A slip on the primary system is activated by impact loading in directions making angles of θ = 17°–64° with respect to the [ 10 1 ¯ 0 ] axis. The phenomenon of the formation of two plastic compression waves propagating at different velocities is observed in samples oriented at angles of 53° and 64°. The spall fracture of single crystal zinc samples oriented in different directions has been measured. It is shown that the highest value of spall strength is recorded along the highly symmetric axis of the crystal. The experimental results presented are consistent with the data published in the scientific literature on beryllium and magnesium and confirm the important role of crystalline anisotropy in the process of inelastic deformation of single crystals. [ABSTRACT FROM AUTHOR]

In this work, the first fabrication and investigation of normally-off single crystal hydrogen-sterminated diamond MOSFETs with Ga2O3 dielectric has been successfully carried out. 50-nm-thick Ga2O3 was deposited by electron-beam evaporation technique at room temperature. The maximum drain current was −36 mA/mm, which was 164 times larger than previous work. Based on the transfer characteristic curve, the threshold voltage, on/off ratio and extrinsic transconductance were −0.37 V, 2.3 × 107, and 9.8 mS/mm, respectively. The effective mobility of the MOSFET was calculated to be 264.1 cm2/V ⋅s at VGS = − 1 V. This work may significantly promote the application of H-diamond FETs. [ABSTRACT FROM AUTHOR]

This study presents systematic investigations into the growth and physical properties of EuAl3Si single crystals, encompassing magnetic, transport, and thermodynamic analyses. EuAl3Si undergoes a ferromagnetic transition at TC = 15 K. A significant reversible magnetocaloric effect was observed around TC. Strikingly, with a small change of magnetic field 2 T, the maximum values of magnetic entropy change (13.4 J/kg K), refrigerant capacity (166 J/kg), and adiabatic temperature change (7.2 K) are found. These parameters, respectively, are 60%, 148%, and 64% larger than those of the parent compound EuAl4 and suggest EuAl3Si as an excellent candidate for magnetic-refrigeration applications near the temperature of liquid hydrogen. The possible mechanism for this enhancement is also discussed. [ABSTRACT FROM AUTHOR]

In this work, the first fabrication and investigation of normally-off single crystal hydrogen-sterminated diamond MOSFETs with Ga2O3 dielectric has been successfully carried out. 50-nm-thick Ga2O3 was deposited by electron-beam evaporation technique at room temperature. The maximum drain current was −36 mA/mm, which was 164 times larger than previous work. Based on the transfer characteristic curve, the threshold voltage, on/off ratio and extrinsic transconductance were −0.37 V, 2.3 × 107, and 9.8 mS/mm, respectively. The effective mobility of the MOSFET was calculated to be 264.1 cm2/V ⋅s at VGS = − 1 V. This work may significantly promote the application of H-diamond FETs. [ABSTRACT FROM AUTHOR]

The search for and fabrication of materials for the near-infrared range of the spectrum, including telecommunication windows, is an extremely important task in modern technology. This work presents the results of studies on the photoluminescence of CsPbCl3 single crystals with varying contents of ytterbium and erbium impurities, grown using the Bridgman method. The existence of electrically neutral Yb3+–VPb–Er3+ complexes within the crystal structure was confirmed. Resonant absorption of excitation radiation λ = 980 nm by Yb3+ ions reveals a three-step energy transfer channel from Yb3+ to Er3+ ions within a single complex. The estimated quantum yield of up-conversion luminescence at λ = 524 nm (0.02%) associated with erbium ions indicates the presence of electronic transitions to higher energy levels, with the possibility of subsequent emission within the third telecommunication window. [ABSTRACT FROM AUTHOR]

High-performance relaxor ferroelectric single crystals, such as Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT), play a crucial role in the applications of medical ultrasonic imaging due to their high piezoelectric properties. In this study, we successfully grew a 2-in. Eu-doped PMN–PT single crystal whose composition variation and electrical properties were systematically investigated. It was found that the PT content of the crystal boule increased gradually along the growth direction, while the change of Eu3+ content was opposite. The property results show that Eu-doped PMN–PT single crystals exhibit a remarkable piezoelectric coefficient of 3300 pC N−1 at DC-poling while maintaining the rhombohedral phase to a tetragonal phase transition temperature (TRT) at 88 °C and the coercive field (EC) at 2.7 kV cm−1, higher to the undoped single crystals. Through the study of the local structure of Eu-PMN–PT, it illustrated that the introduction of Eu3+ increased the standard deviation of an A sublattice from 3.0% to 4.8%. The dopant simultaneously enhanced a tetragonal phase ratio and local structural heterogeneity, resulting in improved piezoelectric properties and temperature stability of the crystal. We further treated the doped crystals with AC-poling to obtain ultrahigh piezoelectric performance (d33 > 4000 pC N−1) and high transparency. This work provides a new approach to achieve a relaxor ferroelectric single crystal with high performance and transparency with good temperature stability, which could be the material of choice for optoelectronic devices in the future. [ABSTRACT FROM AUTHOR]

Metallic nanolaminates are promising materials for nuclear applications due to their ability to withstand extreme radiation environments by trapping irradiation-induced defects. However, the effects of irradiation-induced voids on confined layer slips (CLS) in nanolaminates remain largely unexplored. In this study, molecular dynamics simulations are employed to investigate how void size and location impact CLS in two types of Ag/Cu nanolaminates. Nanolaminated Ag and Ag single crystals are also studied as references. The results show that voids act as obstacles, significantly increasing the critical stress for dislocation glide. The void location plays a role in the critical stress but in different ways for different slip planes. The void-induced hardening is stronger on planes with lower intrinsic critical stress; as a result, adding a void homogenizes the resistance to CLS across different slip planes. Ag/Cu type II nanolaminates, where the two crystals have a "cube-on-cube" crystallographic orientation, demonstrate reduced void-induced hardening compared to type I, where two adjacent layers possess differing crystallographic orientations. In addition, some void-containing nanolaminated Ag show lower critical stress than their single-crystal line counterparts. [ABSTRACT FROM AUTHOR]

Titanium dioxide (TiO2) and strontium titanate (SrTiO3) are widely used photocatalytic materials in photoelectrochemical (PEC) water-splitting processes. Recent advancements have aimed at improving energy conversion efficiency by loading cobalt oxide (CoOx) cocatalysts onto these materials' surfaces to enhance O2 evolution and capture photogenerated holes. Charge carrier recombination plays a crucial role in PEC reactions. This investigation explores the impact of CoOx loading on various crystal faces on the charge carrier recombination dynamics in TiO2 and SrTiO3 single crystals using the microwave photoconductivity decay (μ-PCD) technique. The results indicate that CoOx loading increases the charge carrier recombination for both TiO2 and SrTiO3 across all crystal faces, as observed from the decay curves. Additionally, different tendencies of the injected photon density and temperature dependence of the carrier lifetime, derived from μ-PCD curves, reveal that CoOx loading on TiO2 surfaces introduces the new surface recombination center that dominates the charge carrier recombination. In contrast, for SrTiO3, the surface recombination center remains unchanged across all crystal faces. Consequently, these findings suggest that while CoOx loading on SrTiO3 surfaces does not affect the charge carrier dynamics and remains effective for water splitting, it poses a risk of enhancing carrier recombination and reducing efficiency in TiO2. [ABSTRACT FROM AUTHOR]

The article discusses a theoretical and experimental investigation of the reflection of slow electrons from the surfaces of single-crystal and polycrystalline tungsten thermionic cathodes. The findings challenge traditional ideas as they confirm that the effective reflection coefficient, reff, can reach values close to unity contrary to prior belief. The reason for this occurrence has been established, which is the additional reflection of slow electrons from a potential barrier near polycrystalline surfaces. A method has been developed to separately measure electron reflection coefficients at the surfaces of thermionic cathodes and at the potential barrier of electrode spot fields with different work functions. The study reveals that the maximum values of reff are achieved on polycrystalline surfaces. Additionally, the work functions and reflection coefficients rhkl have been determined for the faces of single crystals of (110), (112), (100), (111), and (116) oriented tungsten. The proposed method enables control over cathode emission inhomogeneity and makes it possible to mitigate the negative effects of secondary electron emission by suppressing electric fields near the cathode surface. [ABSTRACT FROM AUTHOR]

Despite the overwhelming success of organic–inorganic metal halide perovskites in the field of energy harvesting, many of the aspects of these materials are not well understood even now. Specifically, the origin of multiple peaks emergence in photoluminescence (PL) spectra is widely debated. In the present work, emission spectra of mix halide perovskites, MAPb(Br1−xClx)3 (x = 0–1) on single crystal samples, have been investigated in detail. In addition to the band-to-band transition peak, two other peaks were observed. The amplitude of these two additional peaks appears to be strongly dependent on halide composition. Observed extra peaks in PL spectra were seen to be less pronounced in the pure end compositions (x = 0 and 1) and intense for intermediate compositions. It has been observed that multiple peaks seen in the bulk emission spectra are closely related to the coordination chemistry of a halide anion. X-ray absorption near edge spectroscopy indicated the existence of a different environment for the bromine anion, which might be responsible for the modification in the electronic structure with the change in halide composition. This modification in the electronic structure is suggested to be responsible for the appearance of debated multiple peak emissions in the PL spectra. These results are anticipated to pave the way for further research to enhance the understanding of the optoelectronic properties of mixed halide perovskites. [ABSTRACT FROM AUTHOR]

Yttria-stabilized zirconia (YSZ) is found in a wide range of applications, from solid-oxide fuel cells to medical devices and implants. A molecular-level understanding of the hydration of YSZ surfaces is essential for optimizing its performance and durability in these applications. Nevertheless, only a limited amount of literature is available about the surface hydration of YSZ single crystals. In this study, we employ surface-sensitive non-linear vibrational sum frequency generation spectroscopy to investigate the hydration of YSZ(100), (110), and (111) single crystal substrates under ambient laboratory conditions. Three types of hydroxyl groups were identified at all three YSZ–D2O interfaces: (i) hydroxyls on the metal sites of Zr or Y resulting from the dissociative chemisorption of water, (ii) hydroxyls from proton adsorption to O sites formed from water dissociation, and (iii) hydroxyl groups as part of the physisorbed water at the interface. [ABSTRACT FROM AUTHOR]

Electrocaloric effects of adiabatic temperature change via the application of external electric fields are explored for energy-efficient solid-state refrigeration. These effects are typically estimated from the thermodynamic analyses of polarization and field in electrocaloric materials, which implies that higher field application gives larger temperature changes. However, this may not be always true. Here, using both indirect and direct methods, we report an anomalous effect where larger thermal changes occur by applications of lower fields in a multi-domain BaTiO3 (001) single crystal. A large temperature change of 1.9 K under a low field change of 8 kV/cm at 404 K is observed in a multi-domain BaTiO3 (001) single crystal in comparison to that of 1.4 K at a high field change of 30 kV/cm. We attribute this counterintuitive effect to the interplay of the c- and a-domains in the BaTiO3 (001) single crystal under the influence of temperature and field changes. This work provides a fundamental understanding of the complex role of domains in governing the electrocaloric response of ferroelectric materials which is often overlooked but critical for their practical applications. [ABSTRACT FROM AUTHOR]

Metal halide perovskite materials (MHPs) are promising for several applications due to their exceptional properties. Understanding excitonic properties is essential for exploiting these materials. For this purpose, we focus on CsPbBr3 single crystals, which have higher crystal quality, are more stable, and have no Rashba effect at low temperatures compared to other 3D MHPs. We have estimated exciton energy positions, longitudinal-transverse splitting energy, and damping energy using low-temperature reflection spectra. Under high excitation intensity, two biexciton emissions (M-emission) and exciton–exciton scattering emission (P-emission) were observed. We assign the two M-emissions to the emission to the states of longitudinal and transverse excitons, i.e., ML and MT emissions. From the energy position of the MT emission, the biexciton binding energy has been estimated to be ∼2 meV. By analyzing P-emission obtained from the back side of the sample, we have estimated the exciton binding energy to be 17.8–23.7 meV. This estimation minimizes the influence of the wavenumber distribution in the scattering process. In addition, time-resolved transmittance measurements using pulsed white light have revealed the group velocity dispersion. Comparing experimental results with theoretical calculations using the Lorentz model clarifies that exciton dynamics in CsPbBr3 can be described with a simple Lorentz model. These insights enhance the understanding of exciton behavior and support the development of exciton-based devices using MHPs. [ABSTRACT FROM AUTHOR]

To maximize the piezoelectric performance of Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) single crystals, a pulse poling (PP) method is proposed in this study. This study investigates the effects of pulse poling on the piezoelectric and dielectric properties of these PMN–PT single crystals and explores the polarization rotation mechanisms. Our findings indicate a significant improvement in the piezoelectric properties postpulse poling. The optimal PP conditions are identified as 30 pulse numbers at a pulsed electric field of 5 kV/cm. The dielectric constant ɛT33/ɛ0 and piezoelectric coefficient d33 of PMN–0.28PT post PP are 7000–7700 and 2200–2530 pC/N, respectively, representing increases of 49% and 66% compared with those of postdirect current poling (DCP). Additionally, the domain structures of the PMN–0.28PT single crystals after various DCP and PP treatments are examined and compared using piezoelectric force microscopy. The enhanced piezoelectric properties are attributed to the finer domain structures, as well as increased domain wall density achieved through PP. This research introduces a novel domain engineering approach to improve the electromechanical properties of relaxor ferroelectric single crystals. [ABSTRACT FROM AUTHOR]

We explored the feasibility of generating a coherent longitudinal optical (LO) phonon–plasmon coupled mode in an n-type InSb single crystal with the condition that the photo-Dember effect is strongly suppressed and/or eliminated. We systematically performed terahertz time-domain spectroscopic measurements of the n-type InSb single crystal and undoped InSb crystal. The terahertz electromagnetic wave originating from the photo-Dember effect was extinguished in the n-type InSb single crystal, while the clear signal from the photo-Dember effect was detected in the undoped InSb single crystal. Meanwhile we detected the clear signal of the terahertz wave from the coherent LO-phonon–plasmon coupled mode in the n-type InSb single crystal, indicating that the photo-Dember effect is not dominant in the generation of the coherent LO-phonon–plasmon coupled mode although the photo-Dember effect has been attributed to the dominant generation mechanism of the coherent LO-phonon–plasmon coupled mode so far. We explain the present phenomenon, taking account of the fact that the impulsive stimulated Raman scattering process has a possibility of generating coherent LO-phonon–plasmon coupled modes in light-absorbing solids [Nakamura et al., Phys. Rev. B 99, 180301(R) (2019)]. [ABSTRACT FROM AUTHOR]

The configuration of a high-quality security system or computer using a Monte Carlo simulation high-quality random-number generator has been expected. The high-quality random-number generators are obtained using physical randomness phenomena. In particular, chaos is an appropriate random-number generator. First, we investigate the chaotic behavior in the Josephson junction (JJ) under irradiation with external radio frequency (RF) at 77 K using an equivalent circuit of the JJ. JJ is assumed to be an intrinsic JJ in a Bi 2 Sr 2 CaCu 2 O 8 + δ single crystal. The output voltages of the JJ behave chaotic under some conditions and are evaluated using the Lyapunov exponent, Poincaré section, and attractors. Next, random numbers were generated from the chaotic output voltage in rgw JJ under irradiation with RF and evaluated by a verification test. Thus, random-number generators can be applied using the output voltage of theJJ under irradiation with external RF. [ABSTRACT FROM AUTHOR]

Laser-driven shock compression enables an experimental study of phase transitions at unprecedented pressures and temperatures. One example is the shock Hugoniot of magnesium oxide (MgO), which crosses the B1–B2-liquid triple point at 400–600 GPa, 10 000–13 000 K (0.86–1.12 eV). MgO is a major component within the mantles of terrestrial planets and has long been a focus of high-pressure research. Here, we combine time-resolved velocimetry and pyrometry measurements with a decaying shock platform to obtain pressure–temperature data on MgO from 300 to 1500 GPa and 9000 to 50 000 K. Pressure–temperature–density Hugoniot data are reported at 1500 GPa. These data represent the near-instantaneous response of an MgO [100] single crystal to shock compression. We report on a prominent temperature anomaly between 400 and 460 GPa, in general agreement with previous shock studies, and draw comparison with equation-of-state models. We provide a detailed analysis of the decaying shock compression platform, including a treatment of a pressure-dependent optical depth near the shock front. We show that if the optical depth of the shocked material is larger than 1 μm, treating the shock front as an optically thick gray body will lead to a noticeable overestimation of the shock temperature. [ABSTRACT FROM AUTHOR]

Ferroelectric domain walls (DWs) are promising structures for assembling future nano-electronic circuit elements on a larger scale since reporting domain wall currents of up to 1 mA per single DW. One key requirement hereto is their reproducible manufacturing by gaining preparative control over domain size and domain wall conductivity (DWC). To date, most works on DWC have focused on exploring the fundamental electrical properties of individual DWs within single-shot experiments, with an emphasis on quantifying the origins of DWC. Very few reports exist when it comes to comparing the DWC properties between two separate DWs, and literally nothing exists where issues of reproducibility in DWC devices have been addressed. To fill this gap while facing the challenge of finding guidelines for achieving predictable DWC performance, we report on a procedure that allows us to reproducibly prepare single hexagonal domains of a predefined diameter into uniaxial ferroelectric lithium niobate single crystals of 200 and 300 μ m thickness, respectively. We show that the domain diameter can be controlled with an uncertainty of a few percent. As-grown DWs are then subjected to a standard procedure of current-limited high-voltage DWC enhancement, and they repetitively reach a DWC increase of six orders of magnitude. While all resulting DWs show significantly enhanced DWC values, their individual current–voltage (I–V) characteristics exhibit different shapes, which can be explained by variations in their 3D real structure reflecting local heterogeneities by defects, DW pinning, and surface-near DW inclination. [ABSTRACT FROM AUTHOR]

The dynamics of spin and charge-ordered phases in La1.67Sr0.33NiO4 single crystal have been investigated using high-frequency dielectric spectroscopy. The measurements were carried out in frequencies between 0.156 and 316 MHz and temperatures from 50 to 320 K. The intrinsic part of the response by excluding the Maxwell–Wagner relaxation region is obtained below TSDW ∼ 120 K. The intrinsic frequency-dependent real dielectric constant ɛ′ and conductivity σ′ can be well described in terms of the constant phase element revealing a complex charge-hopping process. Our results are in agreement with the spin-density-wave puddles' picture observed by the scanning micro-x-ray diffraction technique. These demonstrate that high-frequency dielectric spectroscopy can be utilized for investigating the various order phases in other transition metal oxides by considering their intrinsic responses. [ABSTRACT FROM AUTHOR]

We have applied positron annihilation spectroscopy to study the vacancy-type defects in β-Ga2O3 single crystals. The three different types of crystals were prepared by Czochralski and edge-defined film-fed growth and doped with Fe, Mg, and Sn for semi-insulating and n-type characteristics. The crystals were also subjected to 6-MeV proton irradiation for controlled introduction of mono-vacancy defects. Positron lifetime and the details of the anisotropy of the Doppler broadening signals were measured as a function of temperature, and the results were compared with the annihilation signals predicted by theoretical calculations. We find Ga vacancies in all three basic split Ga vacancy configurations to dominate the positron data in the as-grown crystals. In contrast, unrelaxed Ga vacancies are found as the main defect introduced by the irradiation. [ABSTRACT FROM AUTHOR]

We have applied positron annihilation spectroscopy to study the vacancy-type defects in β-Ga2O3 single crystals. The three different types of crystals were prepared by Czochralski and edge-defined film-fed growth and doped with Fe, Mg, and Sn for semi-insulating and n-type characteristics. The crystals were also subjected to 6-MeV proton irradiation for controlled introduction of mono-vacancy defects. Positron lifetime and the details of the anisotropy of the Doppler broadening signals were measured as a function of temperature, and the results were compared with the annihilation signals predicted by theoretical calculations. We find Ga vacancies in all three basic split Ga vacancy configurations to dominate the positron data in the as-grown crystals. In contrast, unrelaxed Ga vacancies are found as the main defect introduced by the irradiation. [ABSTRACT FROM AUTHOR]

Magnons are quasiparticles of spin waves, carrying both thermal energy and spin information. Controlling magnon transport processes is critical for developing innovative magnonic devices used in data processing and thermal management applications in microelectronics. The spin ladder compound S r 14 C u 24 O 41 with large magnon thermal conductivity offers a valuable platform for investigating magnon transport. However, there are limited studies on enhancing its magnon thermal conductivity. Herein, we report the modification of magnon thermal transport through partial substitution of strontium with yttrium (Y) in both polycrystalline and single crystalline S r 14 − x Y x C u 24 O 41. At room temperature, the lightly Y-doped polycrystalline sample exhibits 430% enhancement in thermal conductivity compared to the undoped sample. This large enhancement can be attributed to reduced magnon-hole scattering, as confirmed by the Seebeck coefficient measurement. Further increasing the doping level results in negligible change and eventually suppression of magnon thermal transport due to increased magnon-defect and magnon-hole scattering. By minimizing defect and boundary scattering, the single crystal sample with x = 2 demonstrates a further enhanced room-temperature magnon thermal conductivity of 19 W m − 1 K − 1 , which is more than ten times larger than that of the undoped polycrystalline material. This study reveals the interplay between magnon-hole scattering and magnon-defect scattering in modifying magnon thermal transport, providing valuable insights into the control of magnon transport properties in magnetic materials. [ABSTRACT FROM AUTHOR]

Magnons are quasiparticles of spin waves, carrying both thermal energy and spin information. Controlling magnon transport processes is critical for developing innovative magnonic devices used in data processing and thermal management applications in microelectronics. The spin ladder compound S r 14 C u 24 O 41 with large magnon thermal conductivity offers a valuable platform for investigating magnon transport. However, there are limited studies on enhancing its magnon thermal conductivity. Herein, we report the modification of magnon thermal transport through partial substitution of strontium with yttrium (Y) in both polycrystalline and single crystalline S r 14 − x Y x C u 24 O 41. At room temperature, the lightly Y-doped polycrystalline sample exhibits 430% enhancement in thermal conductivity compared to the undoped sample. This large enhancement can be attributed to reduced magnon-hole scattering, as confirmed by the Seebeck coefficient measurement. Further increasing the doping level results in negligible change and eventually suppression of magnon thermal transport due to increased magnon-defect and magnon-hole scattering. By minimizing defect and boundary scattering, the single crystal sample with x = 2 demonstrates a further enhanced room-temperature magnon thermal conductivity of 19 W m − 1 K − 1 , which is more than ten times larger than that of the undoped polycrystalline material. This study reveals the interplay between magnon-hole scattering and magnon-defect scattering in modifying magnon thermal transport, providing valuable insights into the control of magnon transport properties in magnetic materials. [ABSTRACT FROM AUTHOR]

The multiferroic Y-type hexaferrites BaxSr2−xMe2Fe12−yAlyO22 (Me = Zn2+, Co2+, Mg2+, etc.) have attracted much attention due to their giant magnetoelectric (ME) effect up to room temperature and low modulated magnetic field by the chemical doping control of the complex magnetic phases. However, the research of substitution between the Me ions is rare. As doping at the Me ion site can combine the advantages of both, e.g., higher magnetic ordering temperature in Co2 and stronger ME coefficient in Mg2 Y-type hexaferrites, herein, we report the stability and switching of magnetoelectric states in the Y-type hexaferrites Ba0.5Sr1.5CoMgFe11AlO22 single crystals. Our results demonstrate that substituting half of the Mg2+ with Co2+ enhances the transition temperature of the alternating longitudinal conical phase to proper screw spin order up to room temperature compared to those Mg2 Y-type hexaferrites. Simultaneous occurrence of in-plane and out-of-plane ferroelectric polarization is observed, alongside comparable spontaneous magnetization. It was found that the in-plane spin-driven polarization can be reversible below 50 K with a substantial ME coefficient α = −8000 ps/m but becomes irreversible at 100 K. This reversal in the sign of the ME coefficient signifies the transition between two distinct ME states at high temperature. The reversibility and irreversibility of spin-induced polarization are discussed within the framework of free energy based on the ferroelectric phase, which prevail in numerous Y-type hexaferrites. Our results provide insights into understanding the role of the Me ions in the magnetoelectric coupling in Y-type hexaferrites. [ABSTRACT FROM AUTHOR]

The multiferroic Y-type hexaferrites BaxSr2−xMe2Fe12−yAlyO22 (Me = Zn2+, Co2+, Mg2+, etc.) have attracted much attention due to their giant magnetoelectric (ME) effect up to room temperature and low modulated magnetic field by the chemical doping control of the complex magnetic phases. However, the research of substitution between the Me ions is rare. As doping at the Me ion site can combine the advantages of both, e.g., higher magnetic ordering temperature in Co2 and stronger ME coefficient in Mg2 Y-type hexaferrites, herein, we report the stability and switching of magnetoelectric states in the Y-type hexaferrites Ba0.5Sr1.5CoMgFe11AlO22 single crystals. Our results demonstrate that substituting half of the Mg2+ with Co2+ enhances the transition temperature of the alternating longitudinal conical phase to proper screw spin order up to room temperature compared to those Mg2 Y-type hexaferrites. Simultaneous occurrence of in-plane and out-of-plane ferroelectric polarization is observed, alongside comparable spontaneous magnetization. It was found that the in-plane spin-driven polarization can be reversible below 50 K with a substantial ME coefficient α = −8000 ps/m but becomes irreversible at 100 K. This reversal in the sign of the ME coefficient signifies the transition between two distinct ME states at high temperature. The reversibility and irreversibility of spin-induced polarization are discussed within the framework of free energy based on the ferroelectric phase, which prevail in numerous Y-type hexaferrites. Our results provide insights into understanding the role of the Me ions in the magnetoelectric coupling in Y-type hexaferrites. [ABSTRACT FROM AUTHOR]

The unique ability of ferroelectrics to generate high voltage under shock loading is limited by electrical breakdown within the shock-compressed ferroelectric material. Breakdown is a hybrid process of initiation and growth. The possible mechanisms of electrical breakdown in ferroelectric films and bulk ceramics subjected to high-pressure shock loading are discussed and experiments designed to elucidate which mechanisms govern breakdown. Gigapascal shock loading experiments were performed on poled Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3 ferroelectric film specimens in the range of 32–156 μm thickness to determine the dependence of the breakdown field on thickness and on film specimens in the range of 4–16 mm length to determine the dependence of the breakdown field on the duration of shock compression. The resulting breakdown-field vs thickness and breakdown-field vs shock transit time dependencies are consistent with a hybrid electron emission initiation and Joule heating microchannel growth mechanism. Further analysis of data previously obtained on shock-compressed 0.27Pb(In1/2Nb1/2)O3–0.47Pb(Mg1/3Nb2/3)O3–0.26PbTiO3 ferrvoelectric single crystals and Pb(Zr0.65Ti0.35)O3, Pb0.99(Zr0.52Ti0.48)0.99Nb0.01O3, Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3 bulk ceramics is consistent with this dual mechanism. It appears that neither chemical composition nor microstructure (single crystal vs polycrystalline) of the ferroelectric material has a significant effect on the breakdown mechanism in shocked ferroelectrics. [ABSTRACT FROM AUTHOR]