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Effective control of magnetic anisotropy, including perpendicular magnetic anisotropy (PMA) and lateral magnetic anisotropy, is important for the design of low-power and high-density spintronic devices. However, the rarity of oxide materials with PMA and stringent conditions required to control magnetic anisotropy have prevented its large-scale application. Here, we demonstrate that the magnetic anisotropy of SrRuO3 films can be specified on-demand by adjusting the content of Ru vacancies to control the structure of the films. With the increase in Ru vacancies, the structure of SrRuO3 changes from orthorhombic to tetragonal. The field angle dependence of the Hall resistance confirmed that the uniaxial magnetic easy axis of SrRuO3 thin films continuously rotates in the (100)pc crystallographic plane, which is identical to the continuous phase transition. Our results not only provide a way to continuously tune the physical properties of epitaxial oxide films by continuously changing the composition but also help to provide guidance for the on-demand design of spintronic devices.

The layered van der Waals metallic material Fe5− xGeTe2, which has near room-temperature itinerant ferromagnetism, offers unprecedented opportunities to explore exotic phenomena and functionalities as well as prospective uses in spintronic or quantum devices. However, the intriguing magnetic ground state of Fe5− xGeTe2 is quite complicated and remains controversial. In this work, we investigate the magnetic ordering transitions in Fe5− xGeTe2 nanoflakes through magneto-transport measurements. The anomalous Hall resistance increases with rising temperature, reaching its maximum at 100 K. Meanwhile, a clear butterfly-shaped magnetoresistance hysteresis was observed with opposite dependence on the switching field around this critical temperature. All experimental results point to the scenario that Fe5− xGeTe2 transitions from the paramagnetic to ferromagnetic state at 265 K and then evolves to a ferrimagnetic state at 100 K. Our work promotes the understanding of magnetism in Fe5− xGeTe2 and motivates further efforts to develop room-temperature spintronic devices based on Fe5− xGeTe2.

Recently, magnetically intercalated layered transition metal dichalcogenide Fe1/3NbS2 has attracted considerable attention due to its promise for spintronics applications, especially for the demonstration of reversible resistance switching by electrical stimulation below the antiferromagnetic transition temperature. Magneto-transport properties and their correlation to the underlying magnetic configurations are yet to be clarified in Fe1/3NbS2. Herein, we investigate the magneto-transport behavior of antiferromagnet Fe1/3NbS2, demonstrating a complex behavior of the magnetoresistance and unconventional Hall effect. The resistance of this compound displayed metallic behavior and an abrupt decrease at TN. Of particular interest, the positive magnetoresistance is enhanced and it reaches a maximum in the vicinity of Néel temperature as a function of the out-of-plane magnetic field, which is in contrast to most of the antiferromagnets. Meanwhile, the Hall signal showed an unusual nonlinear field-dependence in the same temperature range. Moreover, the magnetoresistance exhibits a significant anisotropy, up to 14% near the Néel temperature. We attributed these unconventional magneto-transport behaviors to the field induced formation of a complex spin texture in Fe1/3NbS2. Our work motivates further efforts on antiferromagnetic spintronic devices based on this intercalated layered transition metal dichalcogenide.

The interplay of internal charge and spin degrees of freedom in diluted magnetic semiconductors (DMSs) determines the magnetic, electrical, and optical properties for desired spintronic devices. However, elusive signs in DMSs, such as Curie temperatures far over 300 K, long-range magnetic order at concentrations of magnetic cations of a few percent, temperature-insensitive, and anhysteretic ferromagnetism, challenge our understanding of magnetism in solids. To approach the truth, the magnetism of Mo-doped BaSnO3 was investigated in this work from experiments to density functional theory (DFT) calculations. Electron spin resonance measurements confirm the existence of oxygen vacancies in the samples, and BaMo0.0625Sn0.9375O3−δ, where δ represents the number of oxygen vacancies, displays much weaker ferromagnetism compared to the DFT results without spin–orbit coupling (SOC). Therefore, a small orbital contribution restored in spin–orbit coupling (SOC) was introduced for the partial density of states and band structure calculations. The modified DFT calculations indicate that the increase in oxygen vacancies leads to an obvious reduction of the total density of states (DOS) near Fermi level (EF), lower dispersity of the conduction band, and deep localized states in the bandgap, which help explain the weak ferromagnetism measured in BaMo0.0625Sn0.9375O3−δ containing considerable oxygen vacancies. This study confirms that the contribution of orbital electron states and defects that were ignored in the conventional explanation should be considered to solve the elusive magnetism in diluted magnetic oxides and offers a guide to improve the magnetism.

Manganites (R1−xAxMnO3, R = rare-earth cation and A = alkali or alkaline earth cation) host an immense number of phases and electronic properties, which can be mainly manipulated through conventional structural control such as metallic cations, oxygen concentration, or misfit strain. However, their practical applications are heavily hindered due to the requirement of rigid synthesis conditions and prolonged treatment time. Herein, a subtle hydrogenation of canonical epitaxial La0.3Sr0.7MnO3 films gives rise to a series of structural transformations ranging from the perovskite to the intermediate state and to the brownmillerite one, accompanied by tunable electronic performances from the antiferromagnetic insulating phase to the weak magnetic insulating one. Moreover, the hydrogenated La0.3Sr0.7MnO3−δ films show an ultra-high magnetic temperature (>400 K). The efficient modulations of the crystalline structure and functionalities of manganite oxides using the facile hydrogenation process enable practical applications of high-temperature magnetic insulators in spintronic devices.

Diluted magnetic semiconductors (DMSs) have drawn much attention due to their potential in spintronics and magnetoelectronics. Transparent conducting oxides, which are characterized by high carrier density and mobility, may provide a platform to realize room-temperature DMS oxides via the carrier-induced ferromagnetism. However, magnetic properties of DMS oxides are sensitive to their stoichiometry, and the magnetic performance of the same material synthesized by different groups or preparation methods may vary greatly. Therefore, it is important to clarify the relationship between the magnetic property and the lattice structure. Here, we investigate the magnetic property of Ru0.037Ba0.963SnO3 powders calcined in different atmospheres. It is demonstrated that for Ru0.037Ba0.963SnO3, the measured ferromagnetism is much weaker than the calculated one, and the ferromagnetism of the samples calcined in oxygen is stronger than that of the samples calcined in air. Electron spin resonance measurements show the existence of oxygen vacancies in Ru0.037Ba0.963SnO3 powders, and the first-principles calculations confirm that oxygen vacancies will suppress the ferromagnetism. This work offers a guide to synthesize diluted magnetic oxides with the desired magnetic property.

Interfacial charge and strain are two coupling effects in semiconductor/ferroelectric epitaxial heterostructures, which are pivotal for use in tailoring functionalities in devices. In this work, La0.04Ba0.96SnO3/0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 heterostructures with varying film thicknesses were prepared in order to understand both charge and strain's contributions to the electric-field induced resistance change. The relative resistance change to the lattice strain remains almost unchanged in those thicker films, while increases a little bit in those thinner films. This slight increase is related to the substrate constraint near the interface and follows Freund's strain relaxation model during the dynamic strain induced by the piezoelectric switch. A depletion layer model was also established to simulate the electroresistance variation from the interfacial charge effect. The depletion layer involves an equilibrium between capture and release of electrons by the acceptor-like defects near the interface region. The resistance change vs electric field evolves from a butterfly-like shape to a square-like when decreasing the film thickness, due to the joint effect of strain and interfacial polarization screening charge. This study provides an insight into understanding heteroepitaxial coupling and exploring their potential applications in oxide electronic devices.

New types of artificial synaptic devices are important to develop highly reliable devices for high-intelligent neuromorphic information technologies. Here, we develop an epitaxial heterostructure with a small-gap spin-orbital-coupling-Mott insulator Sr2IrO4 and a large-gap ferroelectric BaTiO3 to implement robust artificial synapses. Electric-field-dependent synchrotron X-ray absorption spectroscopy indicates that oxygen vacancies are transferred to the bilayer surface by an applied voltage less than 5 V. Because of the epitaxial quality and the large band-gap offset, the prototype devices have robust bipolar-resistance-switching behaviors as demonstrated by the high endurance (>104 cycles) and the long retention (>104 s). The steady synaptic learning algorithm is made in the prototype device with multiple synaptic functions including the short term plasticity, long term plasticity, and spike timing dependent plasticity. Our study demonstrates the ferroelectric/spin-orbital-coupling-Mott oxide bilayer as a reliable prototype device that mimics the synapses in neural systems of the human brain.New types of artificial synaptic devices are important to develop highly reliable devices for high-intelligent neuromorphic information technologies. Here, we develop an epitaxial heterostructure with a small-gap spin-orbital-coupling-Mott insulator Sr2IrO4 and a large-gap ferroelectric BaTiO3 to implement robust artificial synapses. Electric-field-dependent synchrotron X-ray absorption spectroscopy indicates that oxygen vacancies are transferred to the bilayer surface by an applied voltage less than 5 V. Because of the epitaxial quality and the large band-gap offset, the prototype devices have robust bipolar-resistance-switching behaviors as demonstrated by the high endurance (>104 cycles) and the long retention (>104 s). The steady synaptic learning algorithm is made in the prototype device with multiple synaptic functions including the short term plasticity, long term plasticity, and spike timing dependent plasticity. Our study demonstrates the ferroelectric/spin-orbital-coupling-Mott oxide bilayer as ...

Interfacial charge and strain distributions inside artificial perovskite ABO3 heterostructures often affect intriguing physical properties that are important to device performance. Normally, both charge and strain coexist across the interfaces, and their exact roles in determining the properties remain elusive. In the present work, La0.7Sr0.3MnO3 (LSMO) ultrathin films were grown on (001)-0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMNPT) single-crystal substrates to discriminate between the effect of charge and strain on the transport and magnetoelectric properties. In heterostructures with thicker LSMO films, the strain effect dominates the resistance and the magnetic moment depends on the external electric field. With the decreasing LSMO thickness, the butterfly-like resistance–electric-field (R-E) and magnetization–electric-field (M-E) curves become loop-like, indicating that charge effects dominate strain effects in determining the electric field that controls the transport and magnetic properties. Furthermore, soft-x-ray absorption spectra of 32 and 4 nm LSMO/PMNPT samples at the Mn L edge under an applied electric field of ±6 kV/cm indicate that orbital reconstruction also plays an important role in interfacial magnetoelectric coupling.Interfacial charge and strain distributions inside artificial perovskite ABO3 heterostructures often affect intriguing physical properties that are important to device performance. Normally, both charge and strain coexist across the interfaces, and their exact roles in determining the properties remain elusive. In the present work, La0.7Sr0.3MnO3 (LSMO) ultrathin films were grown on (001)-0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMNPT) single-crystal substrates to discriminate between the effect of charge and strain on the transport and magnetoelectric properties. In heterostructures with thicker LSMO films, the strain effect dominates the resistance and the magnetic moment depends on the external electric field. With the decreasing LSMO thickness, the butterfly-like resistance–electric-field (R-E) and magnetization–electric-field (M-E) curves become loop-like, indicating that charge effects dominate ...

We proposed and investigated, by theoretical analyses and simulations, a multi-color and multi-directional radiation by using sheet electron-beams to drive two-dimensional (2D) sub-wavelength hole arrays (SHAs). Each sub-wavelength hole is a resonant and radiative unit, which is successively excited by the electron-beam, such that the 2D SHA becomes a 2D array of radiating units and generates coherent Smith-Purcell radiation in specific directions where the radiation from all the units constructively interferes. The multi-color radiation is obtained when several resonant modes are excited. Each resonant mode could simultaneously radiate at several directions due to the multiple periodicity of the 2D SHA, and the radiation could be steered to any directions in the three dimensional space by adjusting the arrangement of 2D SHA and the electron energy. This radiation could promisingly be developed as radiation sources and devices with broad applications.

Electric-field control of the anomalous Hall effect (AHE) was investigated in Fe40Pt60/(001)-Pb(Mg1/3Nb2/3)0.67Ti0.33O3 (FePt/PMN-PT) multiferroic heterostructures at room temperature. It was observed that a very large Hall resistivity change of up to 23.9% was produced using electric fields under a magnetic field bias of 100 Oe. A pulsed electric field sequence was used to generate nonvolatile strain to manipulate the Hall resistivity. Two corresponding nonvolatile states with distinct Hall resistivities were achieved after the electric fields were removed, thus enabling the encoding of binary information for memory applications. These results demonstrate that the Hall resistivity can be reversibly switched in a nonvolatile manner using programmable electric fields. Two remanent magnetic states that were created by electric-field-induced piezo-strain from the PMN-PT were attributed to the nonvolatile and reversible properties of the AHE. This work suggests that a low-energy-consumption-based approach can be used to create nonvolatile resistance states for spintronic devices based on electric-field control of the AHE.

Transition metal dichalcogenides (TMDs) have emerged as promising candidates for realizing p–n junction device applications. However, the realization of the modulation in the electronic properties of p-type TMDs still remains challenging. Here, we report an enhanced p-type electrical transport behavior in a hybrid structure of graphene quantum dot (GQD)/two dimensional (2D) WSe2. The incorporation of GQDs onto the surface of thin layer WSe2 triggers significantly the charge transfer from WSe2 to GQDs due to the band alignment at the interface. As a result, the increase in the spectral weight of positive charged trions occurs, leading to a red shift in the photoluminescence in the hybrid structure of GQD/WSe2. Because of the charge transfer, it results in 50-time improvement in the hole carrier mobility with a decreased threshold voltage in the hybrid structure compared to pristine WSe2. Our results pave the way for enhancing the performance of other 2D material-based electronic devices.

Bismuth layer structured Aurivillius oxides have long been considered as traditional ferroelectric dielectrics, and they are feasible platforms incubating magnetic, ferroelectric, photonic, microwave, etc. properties for many important applications. It has been a longstanding challenge to achieve a certain charge carrier concentration and to narrow the bandgap in such transition metal complex oxides, yet realizing that semiconductivity is necessary for potential integration functions such as junctions in oxide optoelectronic devices. By inserting La1-xSrxMnO3 into the typical Bi4Ti3O12 ferroelectric host, we demonstrate semiconductivity and large bandgap tuning in Bi4Ti3O12-La1-xSrxMnO3 (0.3 ≤ x ≤ 0.7) solid solutions, in which a minimum resistivity value of ρ = 5021 Ω·cm and an optical bandgap value of Eg = 1.97 eV are obtained. Soft X-ray absorption spectra provide Mn and Ti charge valence states, indicating an almost constant Mn3.2+ state and an increase towards Ti4+ when raising the La/Sr ratio.

Control over nonvolatile magnetization rotation and resistivity change by an electric field in La0.6Sr0.4MnO3 thin films grown on (011) oriented 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 substrates are studied. By utilizing an in-plane strain induced by a side ferroelectric switching with pulsed electric fields from −2.5 kV/cm to +5 kV/cm along [011¯], a nonvolatile and reversible 90°-rotation of the magnetic easy-axis is achieved, corresponding to −69.68% and +174.26% magnetization switching along the [100] and [011¯] directions, respectively. The strain induced nonvolatile resistivity change is approximately 3.6% along the [011¯] direction. These findings highlight potential strategies for electric-field-driven spintronic devices.

We proposed and investigated a terahertz Orotron, which is based on the recently revealed special Smith–Purcell radiation. It overcomes the main obstacles of the traditional Orotron in the terahertz region—unreachable high starting-current-density and low radiation power. With the experimentally available electron beam and facilities, its average output power can reach hundreds of milliwatts and even several watts in terahertz region, which is many orders of magnitude higher than that of the traditional Orotron. Additionally, it can be controlled to operate in ether the first or the second order mode, and the radiation frequency can extend from 0.1 THz to 1 THz. These remarkable advantages make it a promising terahertz source for practical applications.

The combinatorial material chip strategy is used to study the ferroelectric-paraelectric phase boundary of the Ba1−xSrxTiO3 thin film system. The electro-optic (EO) effect at different compositions is measured using a modified direct-current/alternating-current birefringence EO measurement technique. We find that Ba1−xSrxTiO3 thin films exhibit relaxor like behavior with diffused ferroelectric domains existing well past the previously defined ferroelectric-paraelectric boundary (x>0.3).

Erbium-doped Pb(Mg1/3Nb2/3)O3–PbTiO3(PMN–PT) thin films were grown on (10 12) sapphire substrate with a purpose of developing an active optical material combining both the large electro-optic (EO) effect and lasing or amplification functions. Strong characteristic Er3+ intra-4f shell emission around 1.54 μm is observed at room temperature and a compositional quenching occurred at where the Er content is larger than 0.5 mol %. The introduction of Er in PMN–PT decreased the EO effect, but the EO coefficient still maintain a reasonable value, which is about 0.4×10−16 (m/V)2 at Er content of 0.5 mol %. These results indicate that Er3+-doped PMN–PT can be a potential candidate for integrated optic active devices.

Strong electro-optical (EO) anisotropy has been measured in (1−x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 [(1−x)PMN–xPT] single crystalline films epitaxially grown on (100)-cut LaAlO3 substrate, through using an improved dynamic alternating-current ellipsometric null EO detection technique with high accuracy. Large quadratic EO coefficients, which can be as large as 1.38×10−16 (m/V)2 in 0.67PMN–0.33PT film, were obtained in all the used compositions when electric field was applied along {110} directions. The strong EO anisotropy has been explained according to the structural relationship between ferroelectric polarization, input light polarization, and the applied electric field.

The structural and quadratic electro-optic properties in lead magnesium niobate titanate thin films have been systematically studied as a function of the fraction x of lead titanate. (110)-oriented, pyrochlore-free PMN–PT films with PT contents around morphotropic phase boundary compositions, which have a propagation loss as low as 3 dB/cm and a high electro-optical (EO) coefficient of 1.32×10−16 (m/V)2, have been fabricated on (1012)-cut sapphire substrates. The EO measurements show that the PMN–PT is a highly promising electro-optic material.

There is a long-standing challenge in the fabrication of layered oxide epitaxial films due to their thermodynamic phase-instability and the large stacking layer number. Recently, the demand for high-quality thin films is strongly pushed by their promising room-temperature multiferroic properties. Here, we find that by inserting a conducting and lattice matched LaNiO3 buffer layer, high quality m = 5 Bi6FeCoTi3O18 epitaxial films can be fabricated using the laser molecular beam epitaxy, in which the atomic-scale sharp interface between the film and the metallic buffer layer explains the enhanced quality. The magnetic and ferroelectric properties of the high quality Bi6FeCoTi3O18 films are studied. This study demonstrates that insertion of the conducting layer is a powerful method in achieving high quality layered oxide thin films, which opens the door to further understand the underline physics and to develop new devices.

Super-large-period Aurivillius thin films with a pseudo-period of ten were grown on (0 0 1) SrTiO3 substrates using the pulsed laser deposition method. The as-grown films are found to be coherently strained to the substrate and atomically smooth. X-ray diffraction indicates an average periodicity of ten, while analysis with the high resolution scanning transmission electron microscopy reveals a self-modulated nanostructure in which the periodicity changes as the film thickness increases. Finally, we discuss the magnetic and possible ferroelectric properties of the self-modulated large period Aurivillius films at the room temperature.

Effect of a platinum bottom electrode on the SrBi5Fe1−xCoxTi4O18 layered oxide polycrystalline films was systematically studied. The doped cobalt ions react with the platinum to form a secondary phase of PtCoO2, which has a typical Delafossite structure with a weak antiferromagnetism and an exceptionally high in-plane electrical conductivity. Formation of PtCoO2 at the interface partially consumes the cobalt dopant and leads to the structural collapsing from 5 to 4 layers, which was confirmed by X-ray diffraction and high resolution transmission electron microscopy measurements. Considering the weak magnetic contribution from PtCoO2, the observed ferromagnetism should be intrinsic of the Aurivillius compounds. Ferroelectric properties were also indicated by the piezoresponse force microscopy. In this work, the platinum induced secondary phase at the interface was observed, which has a strong impact on Aurivillius structural configuration and thus the ferromagnetic and ferroelectric properties.

A nonlinear dielectric scanning tip microwave near-field microscope capable of submicron quantitative imaging of nonlinear dielectric constant was developed. This nondestructive technique was used to image the nonlinear dielectric constant profiles of an yttrium-doped LiNbO3 single crystal with periodically polarized ferroelectric domains.

Highly (110)-oriented and (100) nearly epitaxial 0.7PMN-0.3PT thin films were deposited on (1012) sapphire and (100) LaAlO3 substrates, respectively, using a dip-coating method. Optical waveguide characterization and electro-optic effect measurements of the film on sapphire substrate were demonstrated. Low propagation loss of 4.1 dB/cm and high quadratic electro-optic coefficient of 0.75×10−16 (m/V)2 were obtained at wavelength of 632.8 nm. Epitaxial PMN-PT thin films will be suitable for integrated optic devices.

A recently developed scanning tip microwave near-field microscope has been improved to achieve a spatial resolution of 100 nm (∼λ/106). Furthermore, explicit calculations of the field distribution using a simplified model allow quantitative microscopy of dielectric properties for dielectric materials. A detection sensitivity of δe/e∼6×10−4 has been achieved.

Picosecond 531 nm green and 385 nm violet light generation through first‐order and third‐order quasiphase matching (QPM) has been performed in a LiNbO3 optical superlattice. The conversion efficiency is 11.4% and 1.6%, respectively. A comparison between theoretical analyses and experimental results of frequency doubling peak value and full width at half‐maximum for both the first‐ and third‐order QPM are given. Possible simultaneous generation of green and violet light in the crystal are predicted for constructing a compact two outputting wavelengths light source.

A LiNbO3 crystal with periodic laminar ferroelectric domain structures (460 domains) was used to generate 430 and 435 nm radiation by quasi‐phase‐matched frequency doubling at room temperature. Blue light output of 0.2 μJ energy was measured for input energy 5 μJ of fundamental wave in pulse operation.

Multiferroic properties of four-layered Bi4.25La0.75Fe0.5Co0.5Ti3O15 ceramics were carefully investigated. X-ray diffraction and high resolution transmission electron microscopy analyses indicate that the as-prepared sample is almost free from secondary phases, and magnetization measurements confirm a ferromagnetic transition ∼483 K. At room temperature (RT), the sample shows a typical ferromagnetism with a remnant magnetization (2Mr) of ∼51.2 m emu/g, and a good ferroelectric hysteresis with a remnant polarization (2Pr) of ∼15.4 μC/cm2. More importantly, an obvious magneto-dielectric (MD) effect has been found under a low magnetic field of 1 T at RT with a maximum of magneto-dielectric constant of ∼10.5%.

Ag/SiO2 core shell nanoparticles can be potentially useful in solar cells with the expectation to enhance light absorption. Thermal stability of such nanoparticles would be an important issue and has not been investigated much in the past. This research studied both morphological and optical absorption changes when heat-treating Ag/SiO2 core shell nanoparticles at various temperatures. At lower temperatures, Ag diffuses out through the porous shell, and remains inside at higher temperatures when the shell becomes solid. The results are instructive to further apply such nanoparticles into solar cells.

Layer-structured, single phase Bi5Fe0.5Co0.5Ti3O15 ceramics was synthesized following a multicalcination procedure. Magnetic moment increases more than three times by substituting half Fe sites by Co ions. The material exhibits an Aurivillius phase with a four-layer unit cell structure, and presents a remarkable coexistence of ferroelectricity and ferromagnetism above room temperature. The measured 2Pr and 2Mr are 13 μC/cm2 and 7.8 memu/g, respectively. The material’s magnetic behavior below 275 °C is relaxationlike and its magnetic Curie temperature is ∼345 °C.

Photoluminescence in Yb3+:Y2O3 thin films grown on sapphire substrates are enhanced using arrays of gold nanoparticles having different shape aspect ratios. The enhanced photoluminescence is attributed to the resonance of localized surface plasmon resonance modes of gold nanoparticles with multiple optical transition lines of the doped Yb3+ ions. Its potential as an effective means for solar cell photon harvesting through efficient frequency shifting is also discussed, considering the demonstrated benefits of broad spectral response and much relaxed tolerance for nanofabrication.

Optical limiting in highly oriented lead magnesium niobate–lead titanate multilayers has been investigated at both 1.064 and 0.532μm wavelengths. Limiting thresholds for three such multilayers having periods of 20, 106, and 218nm, respectively, were determined at the level ∼220μJ/pulse for 1.064μm and ∼150μJ/pulse for 0.532μm. Nonlinear optical scattering from domain walls was used to explain the observed limiting behavior. Possible formation of nonlinear refraction grating was also discussed.

Acoustic superlattices with periods varying gradually are grown by the Czochralski method. The transducer made of the acoustic superlattice is fabricated. The insertion loss measurement shows the transducer has a wide frequency response range.