Extrinsic Contributions Research Articles

Optimizing piezoelectric performance of complex perovskite through increasing diversity of B-site cations

Piezoelectric materials with unique properties are hugely appealing for high sensitivity sensors and ultrasonic transducers. Here, Pb(Ni1/3Nb2/3)O3-Pb(Yb1/2Nb1/2)O3-PbTiO3 piezoelectric system was designed and investigated in detail. The optimized piezoelectric response (d33 = 826 pC/N, d33* = 1017 pm/V) together with good temperature stability and negligible performance degradation up to 106 cycles was achieved in 0.58PNN-0.10PYN-0.32PT composition. Rayleigh analysis revealed the amplification of intrinsic and extrinsic contributions in MPB region due to more spontaneous polarization orientations and an increase in chemical disorder of system after the introduction of PYN. The origin of high piezoelectric response was investigated through the combination of scanning electron microscopy and piezoresponse force microscopy. The diversity of B-site cations was shown to enhance local structural heterogeneity, weaken long-range ferroelectric ordered domains, and lower free energy barrier via the formation of nanodomain configuration that promoted polarization rotation, thereby improving piezoelectric properties of the material. Therefore, it is suggested that increasing the diversity of B-site cations is an effective strategy for achieving outstanding piezoelectric performance.

Deformation Coupled Moiré Mapping of Superlubricity in Graphene.

The ultralow friction of two-dimensional (2D) materials, commonly referred to as superlubricity, has been associated with Moiré superlattices (MSLs). While MSLs have been shown to play a crucial role in achieving superlubricity, the long-standing challenge of achieving superlubricity in engineering has been attributed to surface roughness, which tends to destroy MSLs. Here, we show via molecular dynamics simulations that MSLs alone are not capable of capturing the friction behavior of a multilayer-graphene-coated substrate where similar MSLs persist in spite of significant changes in friction as the graphene coating thickness increases. To resolve this problem, a deformation coupled contact pattern is constructed to describe the spatial distribution of the atomic contact distance. It is shown that as the graphene thickness increases, the interfacial contact distance is determined by a competition between increased interfacial MSLs interactions and reduced out-of-plane deformation of the surface. A frictional Fourier transform model is further proposed to distinguish between intrinsic and extrinsic contributions to friction, with results showing that thicker graphene coatings exhibit lower intrinsic friction and higher sliding stability. These results shed light on the origin of interfacial superlubricity in 2D materials and may guide related applications in engineering.

Texture-based ferroelectric hardening in Na1/2Bi1/2TiO3 -based piezoceramics

${\mathrm{Na}}_{1/2}{\mathrm{Bi}}_{1/2}\mathrm{Ti}{\mathrm{O}}_{3}$-based (NBT-based) ceramics offer a viable option to replace lead-based materials for high-power applications as they are characterized by a stable mechanical quality factor with increasing vibration velocity in comparison to lead-based piezoceramics. Recently, the minor and stable extrinsic contributions were revealed as the origin for the stability of the mechanical quality factor with increasing vibration velocity. This work identifies the very unusual high poling degree as cause for the small extrinsic contributions. To this end, complete pole figure densities have been quantified and correlated to the piezoelectric coefficient and electromechanical quality factor. This hypothesis is further strengthened by correlating the piezoelectric constant (sum of intrinsic and extrinsic contributions) with the remanent polarization (correlates to remanent texturing degree). In order to assess a full picture of NBT-based piezoceramics, $0.94{\mathrm{Na}}_{1/2}{\mathrm{Bi}}_{1/2}\mathrm{Ti}{\mathrm{O}}_{3}\text{\ensuremath{-}}0.06\mathrm{BaTi}{\mathrm{O}}_{3}$ has been considered with and without Zn doping and with quenching. It is compared to $0.79{\mathrm{Na}}_{1/2}{\mathrm{Bi}}_{1/2}\mathrm{Ti}{\mathrm{O}}_{3}\text{\ensuremath{-}}0.21\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}_{1/2}{\mathrm{Bi}}_{1/2}\mathrm{Ti}{\mathrm{O}}_{3}$ with and without Mg doping. Finally, a contrast to soft $\mathrm{Pb}({\mathrm{Zr}}_{1/2}{\mathrm{Ti}}_{1/2}){\mathrm{O}}_{3}$ (PZT) flushes out the impact of domain wall motion on the piezoelectric coefficient and the electromechanical quality factor. Whereas a PZT-based reference material exhibits a linear increase in the piezoelectric constant with increasing remanent polarization, the NBT-based materials deviate from the linear trend, indicating a decrease in extrinsic contributions.

Enhanced magnetic anisotropy induced by praseodymium ferromagnetic order and anomalous transport properties in PrMn2Ge2 single crystals

Anisotropic magnetization and anomalous electrical transport properties of flux-grown $\mathrm{Pr}{\mathrm{Mn}}_{2}{\mathrm{Ge}}_{2}$ single crystals were investigated. The grown crystals exhibit strong magnetic anisotropy with easy magnetization along the $c$ axis. Linear magnetoresistance (MR) and a conventional anomalous Hall effect (AHE) are observed for $H\text{//}c$ and $I\text{//}b$ in contrast to a nonlinear positive MR and a large planar topological Hall effect (PTHE) observed for $H\text{//}a$ and $I\text{//}b$. The anisotropy of the magnetic and electrical transport properties is increased as temperature decreases because magnetic ordering of Pr atoms brings about an increase of the saturation magnetic field of nonlinear MR and the critical field for the maximum values of PTHE. A scaling analysis using the Tian-Ye-Jin model suggests that the AHE in this compound has a larger intrinsic contribution compared to the extrinsic contribution. The nonlinear positive MRs are attributed to the field-induced nontrivial spin textures. The PTHE is related to the real-space skyrmionic bubbles and the noncoplanar spin texture with nonzero spin chirality. These results demonstrate a magnetic field induced anisotropic magnetoresistance and Hall resistivity and its tunability by the ferromagnetic ordering of rare earth atoms in conical-ordered magnets.

Intrinsic and extrinsic anomalous transport properties of the Heusler ferromagnets Fe2CoAl and Fe2NiAl from first principles

Recently, Heusler ferromagnets have been found to exhibit unconventional anomalous electric, thermal, and thermoelectric transport properties. In this study, we employed first-principles density functional theory calculations to systematically investigate both intrinsic and extrinsic contributions to the anomalous Hall effect (AHE), anomalous Nernst effect (ANE), and anomalous thermal Hall effect (ATHE) in two Heusler ferromagnets: Fe$_2$CoAl and Fe$_2$NiAl. Our analysis reveals that the extrinsic mechanism originating from disorder dominates the AHE and ATHE in Fe$_2$CoAl , primarily due to the steep band dispersions across the Fermi energy and corresponding high longitudinal electronic conductivity. Conversely, the intrinsic Berry phase mechanism, physically linked to nearly flat bands around the Fermi energy and gapped by spin-orbit interaction band crossings, governs the AHE and ATHE in Fe$_2$NiAl. With respect to ANE, both intrinsic and extrinsic mechanisms are competing in Fe$_2$CoAl as well as in Fe$_2$NiAl. Furthermore, Fe$_2$CoAl and Fe$_2$NiAl exhibit tunable and remarkably pronounced anomalous transport properties. For instance, the anomalous Nernst and anomalous thermal Hall conductivities in Fe$_2$NiAl attain giant values of 8.29 A/Km and 1.19 W/Km, respectively, at room temperature. To provide a useful comparison, we also thoroughly investigated the anomalous transport properties of Co$_2$MnGa. Our findings suggest that Heusler ferromagnets Fe$_2$CoAl and Fe$_2$NiAl are promising candidates for spintronics and spin-caloritronics applications.

Annealing dependence on magnetization dynamics and two-magnon scattering in Co40Fe40B20 thin films

Investigation of magnetization dynamics of low-damping ferromagnetic layers is of paramount interest for the realization of spin-based electronic devices. Here, we report the effect of surface oxidation on the structural properties, magnetization reversal and spin dynamics of Co40Fe40B20 (CFB) films. X-Ray diffraction results show that both as-deposited and annealed CFB layers up to 250 °C exhibit an amorphous state. Partial crystallization of CoFe is observed in CFB films above 350 °C. Magnetization reversal curves measured using longitudinal magneto-optic Kerr effect indicate a characteristic square loop along the easy axis for all samples. Ferromagnetic resonance (FMR) results show that the resonance field (Hr) shifts due to changes in the structural phase or microstructure. FMR linewidth (ΔH) is linear for both as-deposited and all annealed CFB above 10 GHz, whereas anomalous behaviour in ΔH as a function of frequency is observed below 10 GHz frequency for annealed thin films. The extracted damping parameter manifests extrinsic contributions in the annealed samples compared to the as-deposited. Angular-dependant FMR results show ΔH and Hr exhibit opposite trends in CFB film annealed at 450 °C due to the presence of inhomogeneities. It suggests the signature of two-magnon scattering in the 450 °C annealed CFB. Our systematic study helps in the understanding of the effect of annealing on the crystallinity and magnetization dynamics in CFB thin films.

Improving the piezoelectric properties of Pb(Ni, Nb)O3-Pb(Hf, Ti)O3 ceramics through Nd2O3 addition

High-performance piezoelectric materials, whose displacement is sensitive to an external field and vice versa, are constantly required in electromechanical applications. Here, we introduce Nd3+ ions into 0.49Pb(Nb2/3Ni1/3)O3-0.51Pb(Hf0.3Ti0.7)O3 (PNN-PHT) ceramics via the solid-state method. By constructing a ferroelectric system in the morphotropic phase boundary region and exploiting the synergistic effect of polar nanoregions and an enhanced local structural heterogeneity, excellent piezoelectricity and dielectric properties are obtained. The optimized piezoelectric coefficient d33, dielectric constant ε33, electromechanical coupling factor kp, and dielectric loss tanδ are 1125 pC/N, 8667, 0.66 %, and 1.94 %, respectively. The Vogel-Fulcher law and relaxation analysis were adopted to understand the origin of the high piezoelectricity. The Rayleigh analysis method was used to study the intrinsic and extrinsic contributions to the piezoelectricity of the Nd-doped PNN-PHT ceramics, the extrinsic contribution was found to be up to 19 % in the optimal region (PNN-PHT + 0.4 at. % Nd2O3). Moreover, according to in-situ ferroelectric measurements and fatigue measurements, the PNN-PHT + 0.4 at. % Nd2O3 ceramic exhibits excellent fatigue resistance and stable piezoelectric behavior at 60 ℃. This work provides an approach to realize high-performance piezoelectric ceramics with good electromechanical stability under external condition, which is expected to expand the range of application of piezoelectric materials, e.g., for transducers.

Acceptor doping and actuation mechanisms in Sr-doped BiFeO3[sbnd]BaTiO3 ceramics

BiFeO3-BaTiO3 (BF-BT) ceramics are important multiferroic materials, which are attracting significant attention for potential applications in high temperature lead-free piezoelectric transducers. In the present study, the effects of Sr2+ as an acceptor dopant for Bi3+, in the range from 0 to 1.0% (in mole), on the structure and ferroelectric/piezoelectric properties of 0.7BiFeO3-0.3BaTiO3 ceramics were evaluated. The use of a post-sintering Ar annealing process was found to be an effective approach to reduce electrical conductivity induced by the presence of electron holes associated with reoxidation during cooling. A low Sr dopant concentration (0.3%, in mole) yielded enhanced ferroelectric (Pmax ∼ 0.37 C/m2, Pr ∼ 0.30 C/m2) and piezoelectric (d33 ∼ 178 pC/N, kp ∼ 0.27) properties, whereas higher levels led to chemically heterogeneous core-shell structures and secondary phases with an associated decline in performance. The electric field-induced strain of the Sr-doped BF-BT ceramics was investigated using a combination of digital image correlation macroscopic strain measurements and in-situ synchrotron X-ray diffraction. Quantification of the intrinsic (lattice strain) and extrinsic (domain switching) contributions to the electric field induced strain indicated that the intrinsic contribution dominated during the poling process.

Enhanced Ferroelectric Polarization in Epitaxial BiFeO3−BiMg2/3Nb1/3O3 Films

Remanent polarization is a key parameter of a ferroelectric material. A large remanent polarization is favorable for various ferroelectric applications. Here, we report a large remanent polarization of 116.8 \ensuremath{\mu}C ${\mathrm{cm}}^{\ensuremath{-}2}$ observed in ${\mathrm{Bi}\mathrm{Mg}}_{2/3}{\mathrm{Nb}}_{1/3}{\mathrm{O}}_{3}$ (BMN)-modified ${\mathrm{Bi}\mathrm{Fe}\mathrm{O}}_{3}$ (BFO) thin films, epitaxially deposited on (001)-oriented ${\mathrm{Sr}\mathrm{Ti}\mathrm{O}}_{3}$ substrates buffered with ${\mathrm{La}}_{2/3}{\mathrm{Sr}}_{1/3}{\mathrm{Mn}\mathrm{O}}_{3}$ electrodes. Combined experimental analyses and first-principles calculations reveal that the incorporation of 10 mol % BMN into BFO increases both the intrinsic and extrinsic contributions, resulting in doubled polarization. The intrinsic polarization calculated for BFO-BMN is larger than that of BFO due to enhanced ionic displacements. Compared with epitaxial BFO films in a rhombohedral structure with an interaxial angle of \ensuremath{\alpha} = 89.72\ifmmode^\circ\else\textdegree\fi{} and quasitetragonal c/a = 1.018, the epitaxial BFO-BMN films become more tetragonal-like, with \ensuremath{\alpha} = 89.91\ifmmode^\circ\else\textdegree\fi{} and c/a = 1.037. Moreover, a unique rotated twinning-domain structure is developed in the BFO-BMN thin films, further increasing the out-of-plane polarization by rotating the [111] direction toward the film's normal. These results provide additional opportunities to increase ferroelectric polarization through composition engineering.

QCD at the amplitude level: Fock state interference in heavy quark electroproduction

Quantum chromodynamics (QCD) rigorously predicts the existence of both nonperturbative intrinsic and perturbative extrinsic heavy quark contents of nucleons. In this article we discuss the heavy quark electroproduction on protons induced by the Fock states ∣uud + g〉 of three valence quarks in the proton and a nonperturbative gluon, and the mid uud+Qoverline{Q}Bigrangle non-perturbative state of three valence quarks and a heavy quark-antiquark pair. The first one gives the perturbative contribution when the gluon produces a heavy quark pair, while the second is the intrinsic part, and they produce amplitude interference. We use nonperturbative light-front wavefunctions for these Fock states, which are computed using the color-confining light-front holographic QCD theory. Due to interference of the amplitudes corresponding to the intrinsic and extrinsic heavy quark contribution to the proton a novel Q vs. overline{Q} asymmetry emerges in the differential cross section of the electroproduction off a proton {d}^2{sigma}_{e^{-}p}/left( dxd{Q}^2right) . Our analysis proposed a novel asymmetry in QCD between intrinsic and extrinsic heavy quark content in nucleon and provides new insights into the physics of heavy quark phenomena in QCD at the amplitude level. This asymmetry is similar to the Brodsky-Gillespie asymmetry discovered before in QED case and confirmed at DESY.

Synthesis, magnetic, AC conductivity and dielectric properties of hematite nanocrystallites

We are reporting the synthesis along with magnetic, ac conductivity and dielectric properties of hematite nanocrystallites. The prepared Fe2O3 is crystallizing in corundum structure which belongs to the rhombohedron system with the space group R3-c. The magnetization data shows a typical Morin transition, TN = 265 K for 110 nm crystallites, whereas this transition is decreasing with decrease in crystallite size, TN = 252 K for 33 nm. The value of magnetization is increased with increasing crystallite size. The enhanced dielectric permittivity and ac conductivity were observed in higher hematite crystallite size. The overall dielectric response has revealed conduction mechanism is due to the extrinsic contribution from the dominant Maxwell-Wagner polarization.

Nonlinear Dielectric Response of Relaxor Ferroelectric (1 − x)Pb(Mg1/3Nb2/3)O3 − xPbTiO3 Epitaxial Thin Films

AbstractThin ferroelectric layers are capable of generating large dielectric and electromechanical responses at relatively low voltages, thus can be utilized in various applications including energy storage, energy harvesting, sensors, and actuators. Among ferroelectrics, relaxor ferroelectrics (1 − x)Pb(Mg1/3Nb2/3)O3 − xPbTiO3 are particularly interesting due to their superior dielectric and piezoelectric properties. However, dielectric and piezoelectric responses of the ferroelectric thin films are significantly suppressed relative to their bulk counterparts. The physical mechanism of the properties degradation still remains elusive, which greatly hinders their technological applications. Herein, this work systematically investigates the dielectric nonlinearity and the relationship between composition and intrinsic/extrinsic contributions of high‐quality (1 − x)Pb(Mg1/3Nb2/3)O3 − xPbTiO3 epitaxial thin films (x = 0, 0.1, 0.32) fabricated by pulsed laser deposition. Through the Rayleigh analysis, it is found that the suppression of domain wall motion by substrate clamping is the main cause of thin film performance degradation and is further confirmed by continuous application of background dc bias to extract the dielectric response's intrinsic and extrinsic contributions. This work will pave the way for practical applications of (1 − x)Pb(Mg1/3Nb2/3)O3 − xPbTiO3 thin films in energy storage and electromechanical devices.

Ultrafast Dynamics of Intrinsic Anomalous Hall Effect in the Topological Antiferromagnet Mn_{3}Sn.

We investigate ultrafast dynamics of the anomalous Hall effect (AHE) in the topological antiferromagnet Mn_{3}Sn with sub-100fs time resolution. Optical pulse excitations largely elevate the electron temperature up to 700K, and terahertz probe pulses clearly resolve ultrafast suppression of the AHE before demagnetization. The result is well reproduced by microscopic calculation of the intrinsic Berry-curvature mechanism while the extrinsic contribution is clearly excluded. Our work opens a new avenue for the study of nonequilibrium AHE to identify the microscopic origin by drastic control of the electron temperature by light.

Thermal Modulation of Magnetization Dynamics in Nanometer-Thick L10-FePt Nanogranular and Continuous Films for High-Density Magnetic Recording Media

Thermal modulation of magnetism in magnetic recording media is a novel technique to increase the recording density. L10-FePt is a promising material for the media; however, experimental observation of its magnetization dynamics characterized by the Gilbert damping constant α is technically difficult because the dynamics is in the terahertz (THz) frequency range. A cutting edge technique in THz spintronics, an all-optical pump–probe method, leads us to achieve the detection of THz magnetization dynamics in nanometer-scale thin films with thermal heating. Here, thermal modulation of the magnetization dynamics for L10-FePt nanogranular and continuous films is discussed using the all-optical method. The effective damping constant for the nanogranular film decreased from 0.18 to 0.064 with increasing the temperature, and the thermal modulation decreased the extrinsic contribution, while this increased α above 530 K. This observation regarding the thermal modulation of the magnetic damping is valuable to design future high-density magnetic recording media.

Synergy of lead vacancies and morphotropic phase boundary to promote high piezoelectricity and temperature stability of PBZTN ceramics

• A synergetic strategy including introducing lead vacancies by niobium doping and constructing an morphotropic phase boundary (MPB) was designed to improve the piezoelectricity and temperature stability. • Excellent piezoelectric properties ( d 33 =864 pC/N, k p =84%, T C =201 °C) and high temperature stability (less than 10% variations for electrical properties from 20 °C to 160 °C) are obtained simultaneously in PBZTN-0.540 ceramics. The flourishing development of emerging electromechanical applications has stimulated an urgent demand for ferroelectric ceramics with high piezoelectric properties and broad temperature usage range. However, it remains a challenge to simultaneously obtain good piezoelectricity and reliable temperature stability in lead zirconate titanate (PZT)-based piezoelectric ceramics. To solve this issue, a synergetic strategy was proposed to introduce lead vacancies through niobium doping and construct morphotropic phase boundary (MPB). In this work, Pb 0.905 Ba 0.085 (V Pb″ ) 0.01 [(Zr x Ti 1 -x ) 0.98 Nb 0.02 ]O 3 (PBZTN- x ) material system was designed. Good comprehensive properties ( d 33 = 864 pC/N, k p = 84%, T C = 201°C) and excellent temperature stability (less than 10% variation of electrical properties from 20°C to 160°C) were obtained in PBZTN-0.540 ceramics. Good piezoelectricity can be attributed to high extrinsic contribution (domain wall motion) induced by Pb 2+ vacancies and the existence of nano-domains emerged at MPB, while excellent temperature stability is mainly attributed to the minimized local stress in the lattice and the stable domain structure.

Terahertz Nonlinear Hall Rectifiers Based on Spin-Polarized Topological Electronic States in1T-CoTe2.

The zero-magnetic-field nonlinear Hall effect (NLHE) refers to the second-order transverse current induced by an applied alternating electric field; it indicates the topological properties of inversion-symmetry-breaking crystals. Despite several studies on the NLHE induced by the Berry-curvature dipole in Weyl semimetals, the direct current conversion by rectification is limited to very low driving frequencies and cryogenic temperatures. The nonlinear photoresponse generated by the NLHE at room temperature can be useful for numerous applications in communication, sensing, and photodetection across a high bandwidth. In this study, observations of the second-order NLHE in type-II Dirac semimetal CoTe2 under time-reversal symmetry are reported. This is determined by the disorder-induced extrinsic contribution on the broken-inversion-symmetry surface and room-temperature terahertz rectification without the need for semiconductor junctions or bias voltage. It is shown that remarkable photoresponsivity over 0.1 A W-1 , a response time of approximately 710ns, and a mean noise equivalent power of 1 pW Hz-1/2 can be achieved at room temperature. The results open a new pathway for low-energy photon harvesting via nonlinear rectification induced by the NLHE in strongly spin-orbit-coupled and inversion-symmetry-breaking systems, promising a considerable impact in the field of infrared/terahertz photonics.

Quantum Fluctuation of the Quantum Geometric Tensor and Its Manifestation as Intrinsic Hall Signatures in Time-Reversal Invariant Systems

In time-reversal invariant systems, all charge Hall effects predicted so far are extrinsic effects due to the dependence on the relaxation time. We explore intrinsic Hall signatures by studying the quantum noise spectrum of the Hall current in time-reversal invariant systems, and discover intrinsic thermal Hall noises in both linear and nonlinear regimes. As the band geometric characteristics, quantum geometric tensor and Berry curvature play critical roles in various Hall effects; so do their quantum fluctuations. It is found that the thermal Hall noise in linear order of the electric field is purely intrinsic, and the second-order thermal Hall noise has both intrinsic and extrinsic contributions. In particular, the intrinsic part of the second-order thermal Hall noise is a manifestation of the quantum fluctuation of the quantum geometric tensor, which widely exists as long as Berry curvature is nonzero. These intrinsic thermal Hall noises provide direct measurable means to band geometric information, including Berry curvature related quantities and quantum fluctuation of quantum geometric tensor.

Loss in hollow-core optical fibers: mechanisms, scaling rules, and limits

Over the past few years, progress in hollow-core optical fiber technology has reduced the attenuation of these fibers to levels comparable to those of all-solid silica-core single-mode fibers. The sustained pace of progress in the field has sparked renewed interest in the technology and created the expectation that it will one day enable realization of the most transparent light-propagating waveguides ever produced, across all spectral regions of interest. In this work we review and analyze the various physical mechanisms that drive attenuation in hollow-core optical fibers. We consider both the somewhat legacy hollow-core photonic bandgap technology as well as the more recent antiresonant hollow-core fibers. As both fiber types exploit different guidance mechanisms from that of conventional solid-core fibers to confine light to the central core, their attenuation is also dominated by a different set of physical processes, which we analyze here in detail. First, we discuss intrinsic loss mechanisms in perfect and idealized fibers. These include leakage loss, absorption, and scattering within the gas filling the core or from the glass microstructure surrounding it, and roughness scattering from the air–glass interfaces within the fibers. The latter contribution is analyzed rigorously, clarifying inaccuracies in the literature that often led to the use of inadequate scaling rules. We then explore the extrinsic contributions to loss and discuss the effect of random microbends as well as that of other perturbations and non-uniformities that may result from imperfections in the fabrication process. These effects impact the loss of the fiber predominantly by scattering light from the fundamental mode into lossier higher-order modes and cladding modes. Although these contributions have often been neglected, their role becomes increasingly important in the context of producing, one day, hollow-core fibers with sub-0.1-dB/km loss and a pure single-mode guidance. Finally, we present general scaling rules for all the loss mechanisms mentioned previously and combine them to examine the performance of recently reported fibers. We lay some general guidelines for the design of low-loss hollow-core fibers operating at different spectral regions and conclude the paper with a brief outlook on the future of this potentially transformative technology.

Investigation of the mechanism of the anomalous Hall effects in Cr2Te3/(BiSb)2(TeSe)3 heterostructure

The interplay between ferromagnetism and the non-trivial topology has unveiled intriguing phases in the transport of charges and spins. For example, it is consistently observed the so-called topological Hall effect (THE) featuring a hump structure in the curve of the Hall resistance (Rxy) vs. a magnetic field (H) of a heterostructure consisting of a ferromagnet (FM) and a topological insulator (TI). The origin of the hump structure is still controversial between the topological Hall effect model and the multi-component anomalous Hall effect (AHE) model. In this work, we have investigated a heterostructure consisting of BixSb2−xTeySe3−y (BSTS) and Cr2Te3 (CT), which are well-known TI and two-dimensional FM, respectively. By using the so-called “minor-loop measurement”, we have found that the hump structure observed in the CT/BSTS is more likely to originate from two AHE channels. Moreover, by analyzing the scaling behavior of each amplitude of two AHE with the longitudinal resistivities of CT and BSTS, we have found that one AHE is attributed to the extrinsic contribution of CT while the other is due to the intrinsic contribution of BSTS. It implies that the proximity-induced ferromagnetic layer inside BSTS serves as a source of the intrinsic AHE, resulting in the hump structure explained by the two AHE model.Graphical abstract

Decoding intrinsic and extrinsic contributions for high piezoelectricity of CBT-based piezoelectric ceramics

This study demonstrates the effects of intrinsic and extrinsic contributions on the piezoelectric properties of Nb/Mg co-doped Ca0.6(Na0.5Bi0.5)0.4Bi4Ti4−x(Nb2/3Mg1/3)xO15.