Large negative thermal expansion in the cubic phase of 
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Gautam, K.; Shukla, D. K.; Francoual, S.; Bednarčı́k, J.; Mardegan, J. R. L.; Liermann, Hanns‐Peter; Sankar, Raman; Chou, F. C.; Phase, D. M.; Strempfer, J.

doi:10.1103/physrevb.95.144112

Cited by 15 publications

(13 citation statements)

References 28 publications

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“…The average CTE is obtained from the relative extension of the composite by the temperature change from 30 to 60 °C resulting in −2.28 × 10 −3 K −1 . We note that this value is the highest CTE among materials and composites, and the actuation is reversible (Figure d).…”

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confidence: 83%

“…However, compared to experimental results, the FEM simulations show the mechanical properties instantaneously responding to temperature changes because the model neglects the time delay of heat conduction. Figure f shows the simulated x ‐ and y ‐direction strains as a function of temperature, indicating that our metamaterial has much larger CTEs ( α x = ±6.44 × 10 −4 K −1 and α y = −4.2 × 10 −3 K −1 ) than other negative thermal expansion materials . Furthermore, the metamaterial exhibits a PPR mode below 45 °C and a NPR mode above the temperature.…”

mentioning

confidence: 91%

“…The present work demonstrates a novel strategy that leads to smart mechanical metamaterials with switching between positive and negative Poisson's ratios in response to temperature, where Poisson's ratio is the negative ratio of transverse strain to longitudinal strain. We utilize two‐way shape memory effects to obtain a thermoresponsive rod with an extremely large thermal expansion coefficient, which is the largest value reported thus far . A mechanical model for describing their large‐scale behaviors is further developed to predict their programmable mechanical deformations.…”

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confidence: 99%

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Mechanical Metamaterials with Thermoresponsive Switching between Positive and Negative Poisson's Ratios

Park

Kwon

et al. 2018

Physica Rapid Research Ltrs

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There have been many studies on smart mechanical materials that sensibly deform in response to external stimuli. However, most of the previous studies have focused on structure changes but largely neglected stimuli‐responsive and programmable mechanical properties. Here, we present a novel strategy of mechanical metamaterials, engineered materials with mechanical properties defined by their structure rather than their composition, to design smart materials that change their mechanical properties in response to external stimuli. The present work demonstrates mechanical metamaterials with thermoresponsive and reversible switching between positive and negative Poisson's ratios. In order to realize the thermoresponsive and reversible switching, a thermoresponsive rod with an extremely large thermal expansion coefficient is developed utilizing two‐way shape memory effects. As an application of our metamaterials, we propose soundproofing materials that selectively block sound waves in a specific frequency range depending on temperature.

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confidence: 83%

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confidence: 91%

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confidence: 99%

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Mechanical Metamaterials with Thermoresponsive Switching between Positive and Negative Poisson's Ratios

Park

Kwon

et al. 2018

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“…As the second type of single-phase multiferroic material, CaMn 7 O 12 has ferroelectric properties caused by its special helical magnetic structure, and produces a strong magneto-electric coupling effect. Therefore, CaMn 7 O 12 has potential applications in spin electronics, multi-state storage devices, and microelectromechanical system (MEMS) [6][7][8][9][10][11][12]. In recent years, while there have been more studies on the structure and performance of bulk CaMn 7 O 12 (including single crystals and polycrystalline samples), there have been few studies on CaMn 7 O 12 film [13][14][15][16][17][18].…”

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confidence: 99%

Preparation of Micro-Patterned CaMn7O12 Ceramic Films via a Photosensitive Sol-Gel Method

Wang

Zhao

et al. 2019

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Mn/acetylacetone chelate was synthesized using Mn(CH3COO)2·4H2O as raw material, methanol as the solvent, and acetylacetone as the chelating agent. The ultraviolet (UV)-absorption peak of the synthesized chelate was found around 298 nm. CaMn7O12 sol was subsequently prepared using the Mn/AcAc chelate as the Mn source and calcium nitrate as the calcium source. The UV test indicates that the CaMn7O12 sol has the UV-sensitive characteristics. Owing to its photo-sensitivity, micro-patterned CaMn7O12 ceramic film can be prepared without photoresist, only through dip-coating, drying, UV-irradiation, solvent-washing, and heat treatment. The magnetic test result indicates that the micro-patterned CaMn7O12 ceramic film has a saturation magnetization of 112.8 emu/cm3, which is close to that of non-patterned CaMn7O12 ceramic film.

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“…High-quality CaMn 7 O 12 crystals were grown by the selfflux method, as reported in our earlier study [26]. Details on the crystal structure, characterization, and alignment are provided in the Supplemental Material (see Fig.…”

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confidence: 99%

Magnetic and orbital correlations in multiferroic CaMn7O12 probed by x-ray resonant elastic scattering

et al. 2020

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The quadruple perovskite CaMn 7 O 12 is a topical multiferroic in which the hierarchy of electronic correlations driving structural distortions, modulated magnetism, and orbital order is not well known and may vary with temperature. X-ray resonant elastic scattering (XRES) provides a momentum-resolved tool to study these phenomena, even in very small single crystals, with valuable information encoded in its polarization and energy dependence. We present an application of this technique to CaMn 7 O 12. By polarization analysis, it is possible to distinguish superstructure reflections associated with magnetic order and orbital order. Given the high momentum resolution, we resolve a previously unknown splitting of an orbital-order superstructure peak, associated with a distinct locked-in phase at low temperatures. A second set of orbital-order superstructure peaks can then be interpreted as a second-harmonic orbital signal. Surprisingly, the intensities of the first-and secondharmonic orbital signal show disparate temperature and polarization dependence. This orbital reordering may be driven by an exchange mechanism that becomes dominant over the Jahn-Teller instability at low temperature.

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Large negative thermal expansion in the cubic phase of CaMn7O12

Cited by 15 publications

References 28 publications

Mechanical Metamaterials with Thermoresponsive Switching between Positive and Negative Poisson's Ratios

Mechanical Metamaterials with Thermoresponsive Switching between Positive and Negative Poisson's Ratios

Preparation of Micro-Patterned CaMn7O12 Ceramic Films via a Photosensitive Sol-Gel Method

Magnetic and orbital correlations in multiferroic CaMn7O12 probed by x-ray resonant elastic scattering

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