Pyroelectric thin films - Past, present, and future

Pyroelectrics are a material class that undergoes a change in polarization as the temperature of the system is varied. This effect can be utilized for applications ranging from thermal imaging and sensing to waste-heat energy conversion to thermally driven electron emission. Here, we review recent advances in the study and utilization of thin-film pyroelectrics. Leveraging advances in modeling, synthesis, and characterization has provided a pathway forward in one of the more poorly developed subfields of ferroelectricity. We introduce the complex physical phenomena of pyroelectricity, briefly explore the history of work in this space, and highlight not only new advances in the direct measurement of such effects but also how our ability to control thin-film materials is changing our understanding of this response. Finally, we discuss recent advances in thin-film pyroelectric devices and introduce a number of potentially new directions the field may follow in the coming years

Magnetoelastic coupling in La2/3Sr1/3MnO3 thin films on SrTiO3

Clamping of epitaxial La2/3Sr1/3MnO3 (LSMO) magnetic thin films on SrTiO3 (STO) substrates is shown to promote a clear modification of their magnetic properties at the STO cubic-tetragonal transition. Two distinct mechanisms triggered by the STO transition, namely magnetic domain pattern reconstruction and creation of regions within the magnetically soft LSMO with enhanced magnetic anisotropy, are proposed to be behind the observed anomalous magnetic responses at low ac-magnetic field and at high dc-field, respectively. The persistence of these anomalies in LSMO films as thick as 220 nm shines new light into the magnetoelastic coupling mechanisms across interfaces

Avalanches from charged domain wall motion in BaTiO3 during ferroelectric switching

We report two methods for direct observations of avalanches in ferroelectric materials during the motion of domain walls. In the first method, we use optical imaging techniques to derive changes in domain structures under an electric field. All changes occur through small jumps (jerks) that obey avalanche statistics. In the second method, we analyze jerks by their displacement current. Both methods reveal a power law distribution with an energy exponent of 1.6, in agreement with previous acoustic emission measurements, and integrated mean field theory. This new combination of methods allows us to probe both polarization and strain variations during the motion of domain walls and can be used for a much wider class of ferroelectrics, including ceramic samples, than acoustic emission

Characterization of the recently detected cathinone N-cyclohexyl butylone: From structure elucidation to in silico supported pharmacological/ toxicological considerations

One of the most widely consumed new psychoactive substances (NPS) families in Europe are synthetic cathinones. Cathinone structure can be easily modified resulting in new derivatives that rapidly reach drug markets. In this work, the recently detected synthetic cathinone N-cyclohexyl butylone has been characterized by gas chromatography coupled to mass spectrometry (GC–MS), liquid chromatography coupled to high-resolution mass spectrometry (HRMS), nuclear magnetic resonance (NMR) and Fourier-transformed infrared (FTIR) spectroscopy, using research chemicals samples collected by the drug analysis service Energy Control from anonymous users. Compound identification was performed by the combination of HRMS and NMR data. The elemental composition and putative moieties of the compound were determined based on the accurate-mass ions observed by HRMS. Then, different NMR experiments, including bidimensional, allowed the establishment of the chemical structure and confirmation of compound identity. Furthermore, FTIR spectrum was also acquired in order to provide a complete analytical characterization of the novel cathinone. Finally, pharmacological/toxicological characterization was attempted using in silico methods. Based on these predictions, N-cyclohexyl butylone probably has similar effects to stimulants like MDMA

The metasomatic enrichment of Li in psammopelitic units at San Jose-Valdeflorez, Central Iberian Zone, Spain: a new type of lithium deposit

A new type of Li mineralisation in hard rock has been found to occur in the Valdefórez area (Cáceres, Spain), where there is 111.3 Mt of resources and a mean value of 0.61 wt% of Li2O. Lithium is mainly held by very fne-grained micas, important constituents of Ordovician psammopelitic rocks belonging to the Palaeozoic metasedimentary sequence of the Cáceres syncline. The mineralised zone has an elliptical surface shape with a dimension of~ 700 × 500 m. Lithium-bearing rocks show a characteristic layered appearance, in which light grey quartz-micaceous laminae< 1 mm to some centimetres in thickness, with a variable ratio of quartz to mica, alternate with fne to very fne-grained, dark grey to black tourmalinite laminae parallel to the regional foliation. Subvertical quartz+ (montebrasite)-veins that cut the regional foliation at an extremely high angle are also common in this area. Mineralisation and the associated veins are likely to be linked to the intrusion of the nearby Cabeza de Araya pluton. The infltration of granite-derived Li-, F-, B- and P-rich aqueous fuids into the host rocks through fractures related to shearing processes is considered to be the cause of the formation of Li-rich micas and intense tourmalinisation at the expense of pre-existing phyllosilicates.Spanish Ministerio de Ciencia, Innovacion y Universidades RTI2018-094097-B-100Spanish Ministerio de Ciencia, Innovacion y Universidades (ERDF funds)University of Basque Country GIU18/08

Direct and Fast Screening of New Psychoactive Substances Using Medical Swabs and Atmospheric Solids Analysis Probe Triple Quadrupole with Data-Dependent Acquisition

New psychoactive substances (NPS) have become a serious public health problem, as they are continuously changing their structures and modifying their potency and effects on humans, and therefore, novel compounds are unceasingly appearing. One of the major challenges in forensic analysis, particularly related to the problem of NPS, is the development of fast screening methodologies that allow the detection of a wide variety of compounds in a single analysis. In this study, a novel application of the atmospheric solids analysis probe (ASAP) using medical swabs has been developed. The swab–ASAP was coupled to a triple quadrupole mass analyzer working under a data-dependent acquisition mode in order to perform a suspect screening of NPS in different types of samples as well as on surfaces. The compounds were automatically identified based on the observed fragmentation spectra using an in-house built MS/MS spectra library. The developed methodology was applied for the identification of psychoactive substances in research chemicals and herbal blends. The sensitivity of the method, as well as its applicability for surface analysis, was also assessed by identifying down to 1 μg of compound impregnated onto a laboratory table. Another remarkable application was the identification of cathinones and synthetic cannabinoids on the fingers of potential consumers. Interestingly, our data showed that NPS could be identified on the fingers after being in contact with the product and even after cleaning their hands by shaking off with a cloth. The methodology proposed in this paper can be applied for routine analyses of NPS in different matrix samples without the need to establish a list of target compounds prior to analysis

Surface symmetry-breaking and strain effects on orbital occupancy in transition metal perovskite epitaxial films

The electron occupancy of 3d-orbitals determines the properties of transition metal oxides. This can be achieved, for example, through thin-film heterostructure engineering of ABO(3) oxides, enabling emerging properties at interfaces. Interestingly, epitaxial strain may break the degeneracy of 3d-e(g) and t(2g) orbitals, thus favoring a particular orbital filling with consequences for functional properties. Here we disclose the effects of symmetry breaking at free surfaces of ABO(3) perovskite epitaxial films and show that it can be combined with substrate-induced epitaxial strain to tailor at will the electron occupancy of in-plane and out-of-plane surface electronic orbitals. We use X-ray linear dichroism to monitor the relative contributions of surface, strain and atomic terminations to the occupancy of 3z(2)-r(2) and x(2)-y(2) orbitals in La(2/3)Sr(1/3)MnO(3) films. These findings open the possibility of an active tuning of surface electronic and magnetic properties as well as chemical properties (catalytic reactivity, wettability and so on)

Multiple strain-induced phase transitions in LaNiO3 thin films

Weber, M.C. et al.Strain effects on epitaxial thin films of LaNiO3 grown on different single crystalline substrates are studied by Raman scattering and first-principles simulation. New Raman modes, not present in bulk or fully-relaxed films, appear under both compressive and tensile strains, indicating symmetry reductions. Interestingly, the Raman spectra and the underlying crystal symmetry for tensile and compressively strained films are different. Extensive mapping of LaNiO3 phase stability is addressed by simulations, showing that a variety of crystalline phases are indeed stabilized under strain which may impact the electronic orbital hierarchy. The calculated Raman frequencies reproduce the principal features of the experimental spectra, supporting the validity of the multiple strain-driven structural transitions predicted by the simulations.J.K., M.W., M.G., and J.I. acknowledge support from the National Research Fund, Luxembourg through a Pearl grant (Grant No. FNR/P12/4853155). ICMAB-CSIC authors acknowledge financial support from the Spanish Ministry of Economy and Competitiveness, through the “Severo Ochoa” Programme for Centres of Excellence in R&D (SEV-2015- 0496) and the MAT2014-56063-C2-1-R and MAT2013- 40581-P projects, and from Generalitat de Catalunya (2014 SGR 734). UB authors acknowledge financial support from the Spanish Ministry of Economy and Competitiveness, project MAT2013-41506-P and from Generalitat de Catalunya (2014 SGR 672).Peer reviewe

Glasslike Dynamics of Polar Domain Walls in Cryogenic SrTiO3

Polar and highly mobile domain walls in SrTiO3 move under electric and elastic fields. Two vastly different timescales dominate their dynamical behavior. The previously observed fast changes lead to anomalies near 40 K where the elastic moduli soften and the polarity of the walls becomes strong. Keeping the sample under isothermal conditions leads to a new and unexpected phenomenon: The softening vanishes over timescales of days while the piezoelectricity of the sample remains unchanged. The hardening follows glass dynamics below an onset at T∗≈40  K. The timescale of the hardening is strongly temperature dependent and can be followed experimentally down to 34 K when the relaxation is not completed within two days. The relaxation time of a stretched exponential decay increases exponentially with the decreasing temperature. This relaxation process follows similar dynamics after zero-field cooling and after applying or removing an electric field. The sluggish behavior is attributed to collective interactions of domain patterns following overdamped glass dynamics rather than ballistic dynamics