We report a large and nonvolatile bipolar-electric-field-controlled magnetization at room temperature in a Co40Fe40B20/Pb(Mg1/3Nb2/3)0.7Ti0.3O3 structure, which exhibits an electric-field-controlled looplike magnetization. Investigations on the ferroelectric domains and crystal structures with in~situ electric fields reveal that the effect is related to the combined action of 109\ifmmode^\circ\else\textdegree\fi{} ferroelastic domain switching and the absence of magnetocrystalline anisotropy in Co40Fe40B20. This work provides a route to realize large and nonvolatile magnetoelectric coupling at room temperature and is significant for applications.

Significance: The sun (∼6,000 K) and outer space (∼3 K) are two natural energy resources for humans. However, most of the approaches of energy harvesting from the sun and rejecting energy to outer space are achieved independently using absorbers and emitters with static spectral properties. Herein, a spectrally self-adaptive structure with strong solar absorption and switchable emissivity within the atmospheric window (i.e., 8 to 13 μm) is experimentally demonstrated to achieve diurnal solar thermal and nocturnal radiative cooling efficiently. The experiment shows that the proposed structure not only can be heated to 185°C in diurnal mode but also be cooled to −12°C in nocturnal mode. This work opens new possibilities for continuously efficient energy harvesting utilizing the sun and the universe.

Mechanism of metal-insulator transition (MIT) in strained VO₂ thin films is very complicated and incompletely understood despite three scenarios with potential explanations including electronic correlation (Mott mechanism), structural transformation (Peierls theory) and collaborative Mott-Peierls transition. Herein, we have decoupled coactions of structural and electronic phase transitions across the MIT by implementing epitaxial strain on 13-nm-thick (001)-VO₂ films in comparison to thicker films. The structural evolution during MIT characterized by temperature-dependent synchrotron radiation high-resolution X-ray diffraction reciprocal space mapping and Raman spectroscopy suggested that the structural phase transition in the temperature range of vicinity of the MIT is suppressed by epitaxial strain. Furthermore, temperature-dependent Ultraviolet Photoelectron Spectroscopy (UPS) revealed the changes in electron occupancy near the Fermi energy E_F of V 3d orbital, implying that the electronic transition triggers the MIT in the strained films. Thus the MIT in the bi-axially strained VO₂ thin films should be only driven by electronic transition without assistance of structural phase transition. Density functional theoretical calculations further confirmed that the tetragonal phase across the MIT can be both in insulating and metallic states in the strained (001)-VO₂/TiO₂ thin films. This work offers a better understanding of the mechanism of MIT in the strained VO₂ films.

Instability of emerging perovskite organometallic halide in humidity environment is the biggest obstacle for its potential applications in solar energy harvest and electroluminescent display. Understanding the detailed decay mechanism of these materials in moisture is a critical step towards the final appropriate solutions. As a model study presented in this work, in situ synchrotron radiation x-ray diffraction was combined with microscopy and gravimetric analysis to study the degradation process of CH₃NH₃PbI₃ in moisture and the results reveal that: 1) intermediate monohydrated CH₃NH₃PbI₃·H₂O is detected in the degradation process of CH₃NH₃PbI₃ and the final decomposition products are PbI₂ and aqueous CH₃NH₃I; 2) the aqueous CH₃NH₃I could hardly further decompose into volatile CH₃NH₂, HI or I₂; 3) the moisture disintegrate CH₃NH₃PbI₃ and then alter the distribution of the decomposition products, which leads to an incompletely-reversible reaction of CH₃NH₃PbI₃ hydrolysis and degrades the photoelectric properties. These findings further elucidate the picture of hydrolysis process of perovskite organometallic halide in humidity environment.

Strain has been widely used to manipulate the properties of various kinds of materials, such as ferroelectrics, semiconductors, superconductors, magnetic materials, and [ldquo]strain engineering[rdquo] has become a very active field. For strain-based information storage, the non-volatile strain is very useful and highly desired. However, in most cases, the strain induced by converse piezoelectric effect is volatile. In this work, we report a non-volatile strain in the (001)-oriented Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals and demonstrate an approach to measure the non-volatile strain. A bipolar loop-like S-E curve is revealed and a mechanism involving 109[deg] ferroelastic domain switching is proposed. The non-volatile high and low strain states should be significant for applications in information storage.