HISTONE DEACETYLASE 9 transduces heat signal in plant cells.

Heat stress limits plant growth, development, and crop yield, but how plant cells precisely sense and transduce heat stress signals remains elusive. Here, we identified a conserved heat stress response mechanism to elucidate how heat stress signal is transmitted from the cytoplasm into the nucleus for epigenetic modifiers. We demonstrate that HISTONE DEACETYLASE 9 (HDA9) transduces heat signals from the cytoplasm to the nucleus to play a positive regulatory role in heat responses in Arabidopsis. Heat specifically induces HDA9 accumulation in the nucleus. Under heat stress, the phosphatase PP2AB'ß directly interacts with and dephosphorylates HDA9 to protect HDA9 from 26S proteasome-mediated degradation, leading to the translocation of nonphosphorylated HDA9 to the nucleus. This heat-induced enrichment of HDA9 in the nucleus depends on the nucleoporin HOS1. In the nucleus, HDA9 binds and deacetylates the target genes related to signaling transduction and plant development to repress gene expression in a transcription factor YIN YANG 1-dependent and -independent manner, resulting in rebalance of plant development and heat response. Therefore, we uncover an HDA9-mediated positive regulatory module in the heat shock signal transduction pathway. More important, this cytoplasm-to-nucleus translocation of HDA9 in response to heat stress is conserved in wheat and rice, which confers the mechanism significant implication potential for crop breeding to cope with global climate warming.

Flexoelectric Thin-Film Photodetectors.

The flexoelectric effect, which manifests itself as a strain-gradient-induced electrical polarization, has triggered great interest due to its ubiquitous existence in crystalline materials without the limitation of lattice symmetry. Here, we propose a flexoelectric photodetector based on a thin-film heterostructure. This prototypical device is demonstrated by epitaxial LaFeO3 thin films grown on LaAlO3 substrates. A giant strain gradient of the order of 106/m is achieved in LaFeO3 thin films, giving rise to an obvious flexoelectric polarization and generating a significant photovoltaic effect in the LaFeO3-based heterostructures with nanosecond response under light illumination. This work not only demonstrates a novel self-powered photodetector different from the traditional interface-type structures, such as the p-n and Schottky junctions but also opens an avenue to design practical flexoelectric devices for nanoelectronics applications.

Interface-Charge Induced Giant Electrocaloric Effect in Lead Free Ferroelectric Thin-Film Bilayers.

Conventional refrigeration methods based on compression-expansion cycles of greenhouse gases are environmentally threatening and cannot be miniaturized. Electrocaloric effects driven by electric fields are especially well suited for implementation of built-in cooling in portable electronic devices. However, most known electrocaloric materials present poor cooling performances near room temperature, contain toxic substances, and require high electric fields. Here, we show that lead-free ferroelectric thin-film bilayers composed of (Bi0.5Na0.5)TiO3-BaTiO3 (BNBT) and Ba(Zr0.2Ti0.8)O3-(Ba0.7Ca0.3)TiO3 (BCZT) display unprecedentedly large electrocaloric effects of ∼23 K near room temperature under moderate electric bias. The giant electrocaloric effect observed in BNBT/BCZT bilayers, which largely surpasses the sum of the individual caloric responses measured in BNBT and BCZT, is originated from the presence of compositional bound charges at their interface. Our discovery of interface charge-induced giant electrocaloric effects indicates that multilayered oxide heterostructures hold tremendous promise for developing highly efficient and scalable solid-state cooling applications.

Nano-Ferroelectric for High Efficiency Overall Water Splitting under Ultrasonic Vibration.

Piezocatalysis, converting mechanical vibration into chemical energy, has emerged as a promising candidate for water-splitting technology. However, the efficiency of the hydrogen production is quite limited. We herein report well-defined 10 nm BaTiO3 nanoparticles (NPs) characterized by a large electro-mechanical coefficient which induces a high piezoelectric effect. Atomic-resolution high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and scanning probe microscopy (SPM) suggests that piezoelectric BaTiO3 NPs display a coexistence of multiple phases with low energy barriers and polarization anisotropy which results in a high electro-mechanical coefficient. Landau free energy modeling also confirms that the greatly reduced polarization anisotropy facilitates polarization rotation. Employing the high piezoelectric properties of BaTiO3 NPs, we demonstrate an overall water-splitting process with the highest hydrogen production efficiency hitherto reported, with a H2 production rate of 655 µmol g-1 h-1 , which could rival excellent photocatalysis system. This study highlights the potential of piezoelectric catalysis for overall water splitting.

Metamaterials: A New Ba0.6 Sr0.4 TiO3 -Silicon Hybrid Metamaterial Device in Terahertz Regime (Small 19/2016).

A giant terahertz modulation based on a Ba0.6 Sr0.4 TiO3 -silicon hybrid metamaterial is reported by L. Wu, W. Zhang, and co-workers on page 2610. The proposed nanoscale Ba0.6 Sr0.4 TiO3 (BST) hybrid metamaterial, delivering a transmission contrast of up to ≈79% due to electrically enabled carrier transport between the ferroelectric thin film and silicon substrate, is promising in developing high-performance real world photonic devices for terahertz technology.

A New Ba0.6 Sr0.4 TiO3 -Silicon Hybrid Metamaterial Device in Terahertz Regime.

Metamaterials, offering unprecedented functionalities to manipulate electromagnetic waves, have become a research hotspot in recent years. Through the incorporation of active media, the exotic electromagnetic behavior of metamaterials can be dramatically empowered by dynamic control. Many ferroelectric materials such as BaSrTiO3 (abbreviated as BST), exhibiting strong response to external electric field, hold great promise in both microwave and terahertz tunable devices. A new active Ba0.6 Sr0.4 TiO3 -silicon hybrid metamaterial device, namely, a SRR (square split-ring resonator)-BaSrTiO3 thin film-silicon three-layer structure is fabricated and intensively studied. The active Ba0.6 Sr0.4 TiO3 thin film hybrid metamaterial, with nanoscale thickness, delivers a transmission contrast up to ≈79% due to electrically enabled carrier transport between the ferroelectric thin film and silicon substrate. This work has significantly increased the low modulation rate of ferroelectric based devices in terahertz range, a major problem in this field remaining unresolved for many years. The proposed BST metamaterial is promising in developing high-performance real world photonic devices for terahertz technology.

Novel lead-free ferroelectric film by ultra-small Ba0.8Sr0.2TiO3 nanocubes assembled for a large electrocaloric effect.

A giant electrocaloric effect (ECE) can be achieved in ferroelectric thin films, which demonstrates the applications of thin films in alternative cooling. However, electrocaloric thin films fabricated by conventional techniques, such as the pulsed laser deposition or sol-gel methods, may be limited by high costs, low yield and their dependence on substrates. In this study, we present a new bottom-up strategy to construct electrocaloric Ba0.8Sr0.2TiO3 thin films by assembling precisely designed building blocks of ferroelectric nanocubes, which is supported by detailed structural characterization. Moreover, it is found that our assembled Ba0.8Sr0.2TiO3 films differ remarkably from both individual Ba0.8Sr0.2TiO3 NPs and bulk Ba0.8Sr0.2TiO3 ceramics in terms of new collective ferroelectric properties, including superior and diffused permittivity constants and polarization-electric field loops. Benefiting from these unique ferroelectric properties, a giant ECE (9.1 K) over a broad temperature range (20 °C to 60 °C) is achieved, which is very large in the lead-free oxide film. Clearly, this bottom-up strategy provides a promising pathway for developing high electrocaloric effect devices.

Giant piezoelectricity in potassium-sodium niobate lead-free ceramics.

Environment protection and human health concern is the driving force to eliminate the lead from commercial piezoelectric materials. In 2004, Saito et al. [ Saito et al., Nature , 2004 , 432 , 84 . ] developed an alkali niobate-based perovskite solid solution with a peak piezoelectric constant d33 of 416 pC/N when prepared in the textured polycrystalline form, intriguing the enthusiasm of developing high-performance lead-free piezoceramics. Although much attention has been paid on the alkali niobate-based system in the past ten years, no significant breakthrough in its d33 has yet been attained. Here, we report an alkali niobate-based lead-free piezoceramic with the largest d33 of ∼490 pC/N ever reported so far using conventional solid-state method. In addition, this material system also exhibits excellent integrated performance with d33∼390-490 pC/N and TC∼217-304 °C by optimizing the compositions. This giant d33 of the alkali niobate-based lead-free piezoceramics is ascribed to not only the construction of a new rhombohedral-tetragonal phase boundary but also enhanced dielectric and ferroelectric properties. Our finding may pave the way for "lead-free at last".

Ultrahigh Energy Storage in Tungsten Bronze Dielectric Ceramics Through a Weakly Coupled Relaxor Design.

Dielectric energy-storage capacitors, known for their ultrafast discharge time and high-power density, find widespread applications in high-power pulse devices. However, ceramics featuring a tetragonal tungsten bronze structure (TTBs) have received limited attention due to their lower energy-storage capacity compared to perovskite counterparts. Herein, a TTBs relaxor ferroelectric ceramic based on the Gd0.03 Ba0.47 Sr0.485-1.5 x Smx Nb2 O6 composition, exhibiting an ultrahigh recoverable energy density of 9 J cm-3 and an efficiency of 84% under an electric field of 660 kV cm-1 is reported. Notably, the energy storage performance of this ceramic shows remarkable stability against frequency, temperature, and cycling electric field. The introduction of Sm3+ doping is found to create weakly coupled polar nanoregions in the Gd0.03 Ba0.47 Sr0.485 Nb2 O6 ceramic. Structural characterizations reveal that the incommensurability parameter increases with higher Sm3+ content, indicative of a highly disordered A-site structure. Simultaneously, the breakdown strength is also enhanced by raising the conduction activation energy, widening the bandgap, and reducing the electric field-induced strain. This work presents a significant improvement on the energy storage capabilities of TTBs-based capacitors, expanding the material choice for high-power pulse device applications.

Optimizing high-temperature energy storage in tungsten bronze-structured ceramics via high-entropy strategy and bandgap engineering.

As a vital material utilized in energy storage capacitors, dielectric ceramics have widespread applications in high-power pulse devices. However, the development of dielectric ceramics with both high energy density and efficiency at high temperatures poses a significant challenge. In this study, we employ high-entropy strategy and band gap engineering to enhance the energy storage performance in tetragonal tungsten bronze-structured dielectric ceramics. The high-entropy strategy fosters cation disorder and disrupts long-range ordering, consequently regulating relaxation behavior. Simultaneously, the reduction in grain size, elevation of conductivity activation energy, and increase in band gap collectively bolster the breakdown electric strength. This cascade effect results in outstanding energy storage performance, ultimately achieving a recoverable energy density of 8.9 J cm-3 and an efficiency of 93% in Ba0.4Sr0.3Ca0.3Nb1.7Ta0.3O6 ceramics, which also exhibit superior temperature stability across a broad temperature range up to 180 °C and excellent cycling reliability up to 105. This research presents an effective method for designing tetragonal tungsten bronze dielectric ceramics with ultra-high comprehensive energy storage performance.

Polarity Modulation Induced High Electrostrain Performance with Near-Zero Hysteresis in a (Sr0.7Bi0.2□0.1)TiO3-Based System.

High-precision piezo actuators necessitate dielectrics with high electrostrain performance with low hysteresis. Polarity-modulated (Sr0.7Bi0.2□0.1)TiO3-based ceramics exhibit extraordinarily discrete multiphase coexistence regions: (i) the relaxor phase coexistence (RPC) region with local weakly polar tetragonal (T) and pseudocubic (Pc) short-range polar nanodomains and (ii) the ferroelectric phase coexistence (FPC) region with T long-range domains and Pc nanodomains. The RPC composition features a specially high and pure electrostrain performance with near-zero hysteresis (S ∼ 0.185%, Q33 ∼ 0.038 m4·C-2), which is double those of conventional Pb(Mg1/3Nb2/3)O3-based ceramics. Particular interest is paid to the RPC and FPC with multiscale characterization to unravel local structure-performance relationships. Guided by piezoelectric force microscopy, scanning transmission electron microscopy, and phase-field simulations, the RPC composition with multiphase low-angle weakly polar nanodomains shows local structural heterogeneity and contributes to a flat local free energy profile and thus to nanodomain switching and superior electrostrain performance, in contrast to the FPC composition with a macroscopic domain that shows stark hysteresis. This work provides a paradigm to design high-precision actuator materials with large electrostrain and ultralow hysteresis, extending our knowledge of multiphase coexistence species in ferroelectrics.

Achieving Good Temperature Stability of Dielectric Constant by Constructing Composition Gradient in (Pb1-x,Lax)(Zr0.65,Ti0.35)O3 Multilayer Thin Films.

Ferroelectrics with a high dielectric constant are ideal materials for the fabrication of miniaturized and integrated electronic devices. However, the dielectric constant of ferroelectrics varies significantly with the change of temperature, which is detrimental to the working stability of electronic devices. This work demonstrates a new strategy to design a ferroelectric dielectric with a high temperature stability, that is, the design of a multilayer relaxor ferroelectric thin film with a composition gradient. As a result, the fabricated up-graded (Pb,La)(Zr0.65,Ti0.35)O3 multilayer thin film showed a superior temperature stability of the dielectric constant, with variation less than 7% in the temperature range from 30 °C to 200 °C, and more importantly, the variation was less than 2.5% in the temperature range from 75 °C to 200 °C. This work not only develops a dielectric material with superior temperature stability, but also demonstrates a promising method to enhance the temperature stability of ferroelectrics.

Achieving Ultrahigh Energy-Storage Density with Excellent Thermal Stability in Sr0.7Bi0.2TiO3-Based Relaxors via Polarization Behavior Modulation.

Dielectric capacitors possessing the inherent superiorities of high power density and ultrafast charge-discharge speed make their utilization in energy-storage devices extremely propitious, although the relatively low recoverable energy-storage density (Wrec) may impede their applications. In this work, unlike the mainstream approach of destroying long-range ferroelectric/antiferroelectric order and inducing relaxor properties to achieve a high Wrec value, we have selected end members with a high polarization gene to promote the polarization behavior of the typical relaxor Sr0.7Bi0.2TiO3. Therefore, an ultrahigh Wrec ∼ 8 J/cm3 and a superior efficiency (η) ∼ 91% are accomplished in the 0.98[0.56(Sr0.7Bi0.2)TiO3-0.44(Bi0.5Na0.5)TiO3]-0.02 Bi(Mg0.5Ti0.5)O3 sample. The achieved Wrec value is record high in Sr0.7Bi0.2TiO3-based systems as far as we know. The polarization-enhancement behavior can be explained by the phase field simulation results, phase content variance in X-ray diffraction Rietveld refinement, hardening trend in Raman spectroscopy, domain morphology, and local symmetry in transmission electron microscope analysis. Meanwhile, the ceramic possesses excellent thermal stability (ΔWrec < 12.7% and Δη < 10.4%, -50-200 °C), frequency (ΔWrec < 2.69% and Δη < 2.06%, 0.5-500 Hz), and fatigue-resistant stability (ΔWrec < 0.08% and Δη < 0.2%, up to 1 × 105 cycles). Accordingly, this work proposes a design idea to tailor the polarization behavior and energy-storage properties of typical relaxors.

High Energy Density and Temperature Stability in PVDF/PMMA via In Situ Polymerization Blending.

Dielectrics with improved energy density have long-standing demand for miniature and lightweight energy storage capacitors for electrical and electronic systems. Recently, polyvinylidene fluoride (PVDF)-based ferroelectric polymers have shown attractive energy storage performance, such as high dielectric permittivity and high breakdown strength, and are regarded as one of the most promising candidates. However, the non-negligible energy loss and inferior temperature stability of PVDF-based polymers deteriorated the energy storage performance or even the thermal runaway, which could be ascribed to vulnerable amorphous regions at elevated temperatures. Herein, a new strategy was proposed to achieve high energy density and high temperature stability simultaneously of PVDF/PMMA blends by in situ polymerization. The rigidity of the amorphous region was ideally strengthened by in situ polymerization of methyl methacrylate (MMA) monomers in a PVDF matrix to obtain PVDF/PMMA blends. The atomic force microscopic study of the microstructure of etched films showed the ultra-homogenous distribution of PMMA with high glass transition temperature in the PVDF matrix. Consequently, the temperature variation was remarkably decreased, while the high polarization response was maintained. Accordingly, the high energy density of ∼8 J/cm3 with ∼80% efficiency was achieved between 30 and 90 °C in PVDF/PMMA films with 39-62% PMMA content, outperforming most of the dielectric polymers. Our work could provide a general solution to substantially optimize the temperature stability of dielectric polymers for energy storage applications and other associated functions.

Enhanced charge separation in La2NiO4 nanoplates by coupled piezocatalysis and photocatalysis for efficient H2 evolution.

Photocatalytic hydrogen evolution is one promising method for solar energy conversion, but the rapid charge recombination limits its efficiency. To this end, in this work, grain size, and hence the charge carrier migration path, is reduced by lowering the synthesis temperature of two-dimensional visible light-responsive La2NiO4 perovskite. Interestingly, the hydrogen yield for the piezoelectric response of La2NiO4 under only 40 kHz ultrasonic vibration is as high as 680 µmol h-1 g-1, which is 80 times that under only 600 mW cm-2 visible light irradiation. More surprisingly, the hydrogen production rate under both light illumination and ultrasonic vibration is 129 times higher than under visible light irradiation alone. Clearly, a synergistic effect exists between piezocatalysis and photocatalysis. The hydrogen production activity of the samples with water splitting can reach 1097 µmol h-1 g-1 without any sacrificial reagent or co-catalyst, when the light intensity reaches about 1000 mW cm-2, which is a much higher hydrogen evolution rate by piezo-photocatalysis than is achieved by either piezocatalysis or photocatalysis individually. Further analysis indicates that the internal electric field generated by deformation of the La2NiO4 edge under piezoelectric action facilitates the directional separation and migration of photogenerated charges, which in turn significantly enhances the efficiency of use of photogenerated charges for hydrogen production. The investigation here provides a novel approach to design a new reaction system for hydrogen production by coupling multiple external physical fields.

New Degree of Freedom in Determining Superior Piezoelectricity at the Lead-Free Morphotropic Phase Boundary: The Invisible Ferroelectric Crossover.

The morphotropic phase boundary (MPB) in lead-free ferroelectrics, starting from a quadruple point (QP), often displays large piezoelectric responses due to the flattened free-energy profiles. In this work, we found that the QP composition rendering most flattened energy profiles could also exhibit abnormally low piezoelectric constants in Hf-doped BaTiO3. Such an anomaly in the strength of piezoelectricity can be ascribed to the progressive influence of additional strain heterogeneity induced by the substitution of Hf4+ for Ti4+ in BaTiO3, which was overlooked previously. An intermediate level of strain heterogeneity can form an invisible ferroelectric crossover consisting of both micro- and nanodomains, resulting in a large elastic softening and high piezoelectricity. With a further increase in the level of strain heterogeneity, the extinction of regular ferroelectric domain structures and pinned polar dynamics resulted in the feeble piezoelectric outputs near the QP composition. Impressively, a giant d33 of ∼610 pC/N has been accordingly obtained through employing a ferroelectric crossover at off-QP composition in Zr-doped BaTiO3, further underpinning the critical role of uncovered ferroelectric crossover on piezoelectricity along MPB. This work offers another degree of freedom in the design of high-performance eco-friendly piezoelectric ceramics.

Enhancing Comprehensive Energy Storage Properties in Tungsten Bronze Sr0.53Ba0.47Nb2O6-Based Lead-free Ceramics by B-Site Doping and Relaxor Tuning.

Dielectric ceramics with relaxor characteristics are promising candidates to meet the demand for capacitors of next-generation pulse devices. Herein, a lead-free Sb-modified (Sr0.515Ba0.47Gd0.01) (Nb1.9-xTa0.1Sbx)O6 (SBGNT-based) tungsten bronze ceramic is designed and fabricated for high-density energy storage capacitors. Using a B-site engineering strategy to enhance the relaxor characteristics, Sb incorporation could induce the structural distortion of the polar unit BO6 and order-disorder distribution of B-site cations as well as the modulation of polarization in the SBGNT-based tungsten bronze ceramic. More importantly, benefiting from the effective inhibition of abnormal growth of non-equiaxed grains, Sb introduction into SBGNT-based ceramics could effectively suppress the conductivity and leakage current density, enhancing the breakdown strength, as proved by the electrical impedance spectra. Consequently, a remarkable comprehensive performance via balancing recoverable energy density (∼3.26 J/cm3) and efficiency (91.95%) is realized simultaneously at 380 kV/cm, which surpasses that of the pristine sample without the Sb dopant (2.75 J/cm3 and 80.5%, respectively). The corresponding ceramics display superior stability in terms of fatigue (105 cycles), frequency (1∼200 Hz), and temperature (20∼140 °C). Further charge-discharge analysis indicates that a high power density (89.57 MW/cm3) and an impressive current density (1194.27 A/cm2) at 150 kV/cm are achieved simultaneously. All of the results demonstrate that the tungsten bronze relaxors are indeed gratifying lead-free candidate materials for dielectric energy storage applications.

Domain Engineered Lead-Free Ceramics with Large Energy Storage Density and Ultra-High Efficiency under Low Electric Fields.

Dielectric energy storage materials are becoming increasingly popular due to their potential superiority, for example, excellent pulse performance as well as good fatigue resistance. Although numerous studies have focused on lead-free dielectric materials which possess outstanding energy storage characteristics, the results are still not satisfying in terms of achieving both large discharging energy density (Wd) and high discharging efficiency (η) under low electric fields, which is crucial to be conducted in miniatured electronic components. Here, we adopt the strategy of domain engineering to develop sodium bismuth titanate (Bi0.5Na0.5TiO3)-based ceramics employed in the low-field situation. Remarkably, a large Wd of 2.86 J/cm3 and an ultrahigh η of 90.3% are concurrently obtained in 0.94(Bi0.5Na0.5)0.65(Ba0.3Sr0.7)0.35TiO3-0.06 Bi(Zn2/3Nb1/3)O3 system when the electric field is as low as 180 kV/cm. Additionally, the ceramic shows brilliant thermal endurance (20-160 °C) and frequency stability (0.1-100 Hz) with high Wd (>1.48 J/cm3) together with an ultra-high η (>90%). What's more, the ceramic displays a fast charge-discharge time (t0.9 = 109.2 ns). The piezoresponse force microscopy (PFM) results reveal that the introduced Bi(Zn2/3Nb1/3)O3 disrupts the microdomains of (Bi0.5Na0.5)0.65(Ba0.3Sr0.7)0.35TiO3 ceramics and promotes the formation of nanodomains, leading to enhanced energy storage properties. The current work may arouse interest in developing low-field high-performing dielectric capacitors for energy storage application.

Atomic-scale fatigue mechanism of ferroelectric tunnel junctions.

Ferroelectric tunnel junctions (FTJs) are promising candidates for next-generation memories due to fast read/write speeds and low-power consumptions. Here, we investigate resistance fatigue of FTJs, which is performed on Pt/BaTiO3/Nb:SrTiO3 devices. By direct observations of the 5­unit cell­thick BaTiO3 barrier with high-angle annular dark-field imaging and electron energy loss spectroscopy, oxygen vacancies are found to aggregate at the Pt/BaTiO3 interface during repetitive switching, leading to a ferroelectric dead layer preventing domain nucleation and growth. Severe oxygen deficiency also makes BaTiO3 lattices energetically unfavorable and lastly induces a destruction of local perovskite structure of the barrier. Ferroelectric properties are thus degraded, which reduces barrier contrast between ON and OFF states and smears electroresistance characteristics of Pt/BaTiO3/Nb:SrTiO3 FTJs. These results reveal an atomic-scale fatigue mechanism of ultrathin ferroelectric barriers associated with the aggregation of charged defects, facilitating the design of reliable FTJs and ferroelectric nanoelectronic devices for practical applications.

Coupling between phase transitions and glassy magnetic behaviour in Heusler alloy Ni50Mn34In8Ga8.

The transition sequence in the Heusler alloy Ni50Mn34In8Ga8 has been determined from measurements of elasticity, heat flow and magnetism to be paramagnetic austenite → paramagnetic martensite → ferromagnetic martensite at ∼335 and ∼260 K, respectively, during cooling. The overall pattern of elastic stiffening/softening and acoustic loss is typical of a system with bilinear coupling between symmetry breaking strain and the driving structural/electronic order parameter, and a temperature interval below the transition point in which ferroelastic twin walls remain mobile under the influence of external stress. Divergence between zero-field-cooling and field-cooling determinations of DC magnetisation below ∼220 K indicates that a frustrated magnetic glass develops in the ferromagnetic martensite. An AC magnetic anomaly which shows Vogel-Fulcher dynamics in the vicinity of ∼160 K is evidence of a further glassy freezing process. This coincides with an acoustic loss peak and slight elastic stiffening that is typical of the outcome of freezing of ferroelastic twin walls. The results suggest that local strain variations associated with the ferroelastic twin walls couple with local moments to induce glassy magnetic behaviour.