Article
Physics, Multidisciplinary
A. O. Scheie, E. A. Ghioldi, J. Xing, J. A. M. Paddison, N. E. Sherman, M. Dupont, L. D. Sanjeewa, Sangyun Lee, A. J. Woods, D. Abernathy, D. M. Pajerowski, T. J. Williams, Shang-Shun Zhang, L. O. Manuel, A. E. Trumper, C. D. Pemmaraju, A. S. Sefat, D. S. Parker, T. P. Devereaux, R. Movshovich, J. E. Moore, C. D. Batista, D. A. Tennant
Summary: We demonstrate the close proximity of the delafossite material KYbSe2 to the triangular-lattice Heisenberg quantum spin liquid. Using neutron scattering, we identify multipartite entanglement and analyze the magnetic-exchange couplings to confirm its proximity to the theoretical quantum spin-liquid phase. The experimental results are consistent with theoretical models, and a second-order quantum phase transition is observed.
Article
Materials Science, Multidisciplinary
Seungyeol Lee, Beom Hyun Kim, Maeng-Je Seong, Kwang-Yong Choi
Summary: The electronic structure, low-lying excitations, and lattice instabilities of K2IrCl6 have been investigated using Raman spectroscopy and numerical calculations. The results reveal the occurrence of local noncubic distortions at low temperatures and the presence of multiple spin-orbit excitons at high energies.
Article
Physics, Condensed Matter
I. N. Apostolova, A. T. Apostolov, J. M. Wesselinowa
Summary: The study reveals the geometric ferroelectricity in AgCrS2, which can be explained by atomic displacements and described by the transverse Ising model.
SOLID STATE COMMUNICATIONS
(2021)
Article
Materials Science, Multidisciplinary
A. V. Syromyatnikov
Summary: In this study, a spin-1/2 Heisenberg antiferromagnet on the triangular lattice was discussed using the bond-operator technique (BOT). It was found that high-energy collective excitations and another high-energy quasiparticle exist in the system. Quantum fluctuations considerably alter the properties of conventional magnons, and the anomalous spin dynamics observed experimentally recently cannot be described by SWT.
Article
Materials Science, Multidisciplinary
J. Okamoto, A. Chainani, Z. Y. Chen, H. Y. Huang, A. Singh, T. Sasagawa, D. I. Khomskii, A. Fujimori, C. T. Chen, D. J. Huang
Summary: In this study, x-ray spectral evidence is presented for the evolution of valence- and spin-specific tetragonal distortions in single-layer cobaltates. The measurements reveal changes in tetragonal splitting of high-spin Co2+ and low-spin Co3+ states as Sr-doping increases, shedding light on the origin of magnetic anisotropy and in-plane resistivity changes in mixed-valence cobaltates.
Article
Materials Science, Multidisciplinary
Yuan Gao, Yu-Chen Fan, Han Li, Fan Yang, Xu-Tao Zeng, Xian-Lei Sheng, Ruidan Zhong, Yang Qi, Yuan Wan, Wei Li
Summary: The recently synthesized NBCP compound is found to be an ideal realization of a S = 1/2 triangular-lattice antiferromagnet with significant easy-axis spin exchange anisotropy. By combining automatic parameter searching and tensor-network simulations, a microscopic model is established to accurately describe the material's properties, fitting well with experimental data.
NPJ QUANTUM MATERIALS
(2022)
Article
Chemistry, Physical
Yuji Ikeda, Konstantin Gubaev, Jorg Neugebauer, Blazej Grabowski, Fritz Kormann
Summary: Recent experiments have shown that the chemical composition of body-centered cubic (bcc) refractory high entropy alloys (HEAs) can be adjusted to enhance transformation-induced plasticity (TRIP), leading to improved ductility. A method utilizing symmetry analysis and ab initio calculations has been developed to identify the impact of local lattice distortions on the phase stability of HEAs.
NPJ COMPUTATIONAL MATERIALS
(2021)
Article
Chemistry, Physical
Yuan-Yuan Tan, Ming-Yao Su, Zhou-Can Xie, Zhong-Jun Chen, Yu Gong, Li-Rong Zheng, Zhan Shi, Guang Mo, Yong Li, Ling-Wei Li, Hai-Ying Wang, Lan-Hong Dai
Summary: A distinguishing feature of high-entropy alloys (HEAs) is the well-defined crystalline structure with chemical disorder. Local lattice distortion in HEAs is challenging and rarely related to chemical compositions. The study found that average lattice distortions are subtle, with a certain order of magnitude for specific alloying elements, and the flexibility of local electron structure might contribute to local lattice distortions.
Article
Physics, Multidisciplinary
Wang Zhe, Xu Jie-Min, Wang Wen-Jun, Li He-Xuan, Zou You-Ming, Yu Lu, Qu Zhe
Summary: This study investigates the properties of trinagular oxide MnSb2O6 and reveals its unique magnetic and multiferroic behaviors, such as the selection of a single ferroelectric domain and the reversal of electric polarization induced by an external magnetic field. The measurements of magnetic susceptibility, magnetization, and electron spin resonance parameters provide insights into the magnetic structure and characteristics of MnSb2O6.
ACTA PHYSICA SINICA
(2022)
Article
Physics, Multidisciplinary
Katja Biswas
Summary: This article compares enhanced disconnectivity graphs for three different models of spin systems constrained to an Archimedean triangular lattice. The graphs show clear differences in structure for the three models, indicating different accessibility of ground states. The graphs can serve as a tool for understanding the difficulties faced by optimization routines and their effectiveness. Additionally, the graphs provide detailed insight into the structure of the energy landscape.
PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS
(2023)
Article
Materials Science, Multidisciplinary
Hodaka Kikuchi, Shinichiro Asai, Hirotaka Manaka, Masato Hagihala, Shinichi Itoh, Takatsugu Masuda
Summary: We conducted inelastic neutron scattering experiments to investigate the spin dynamics of CsCrF4, a potential spin tube material. The compound undergoes a phase transition from a paramagnetic phase to an intermediate-temperature phase and finally to a low-temperature phase. By comparing observed and calculated neutron spectra, we identified the spin Hamiltonian as antiferromagnetic spin tubes with perturbative terms. The phase diagram for the ground state was calculated and the spin Hamiltonian parameters obtained from the low-temperature phase spectra were close to the boundary of the intermediate-temperature phase.
Article
Chemistry, Physical
Sahil Tippireddy, Feridoon Azough, Vikram, Animesh Bhui, Philip Chater, Demie Kepaptsoglou, Quentin Ramasse, Robert Freer, Ricardo Grau-Crespo, Kanishka Biswas, Paz Vaqueiro, Anthony Powell
Summary: Partial substitution of germanium in chalcopyrite leads to an enhancement of thermoelectric properties due to local structural distortion, lattice softening, and the appearance of resonant phonon modes. The weak chemical bonding of germanium with sulphur also contributes to a high Seebeck coefficient and an improvement in the power factor.
JOURNAL OF MATERIALS CHEMISTRY A
(2022)
Article
Materials Science, Multidisciplinary
Ganesh Kumar Nayak, Andreas Kretschmer, Paul H. Mayrhofer, David Holec
Summary: High entropy alloys (HEAs) have attracted significant attention for their unique structural stability and excellent properties. The concept of high entropy has also been applied to protective coatings. Ab initio calculations reveal the atomic-level behavior of HEAs, particularly focusing on the interplay between high entropy, sluggish diffusion, and lattice distortions in HESN ceramics. The study shows that high entropy alone does not guarantee slow diffusion, and proposes a relationship between local distortions and activation energies. These findings emphasize the need to analyze each system individually to understand the core effects of HEAs.
Article
Materials Science, Ceramics
Yubin Wen, Yufu Liu
Summary: High-entropy oxides with novel structures are being explored for potential high-temperature applications. This study used advanced microscopy techniques to observe and analyze the lattice distortions in a high-entropy fluorite oxide. It was found that the random distribution of cations and oxygen vacancies led to variations in atomic column projections and bond angles, while strain distributions within the crystal structure were centered around +/- 4% and showed alternating positive and negative values.
CERAMICS INTERNATIONAL
(2023)
Article
Materials Science, Multidisciplinary
Yuki Kojima, Nobuyuki Kurita, Hidekazu Tanaka, Kenji Nakajima
Summary: This article reports on the magnetic orderings and excitations in Ba2CoTeO6 composed of two subsystems. The excitation spectra of both subsystems are independent and well separated. The Ising-like subsystem shows stripy ordering, while the other subsystem exhibits elastic scattering.
Article
Chemistry, Multidisciplinary
Pierre Bouvier, Alireza Sasani, Eric Bousquet, Mael Guennou, Joaquim Agostinho Moreira
Summary: This study investigated the lattice dynamics of lead vanadate (PbVO3) using Raman spectroscopy and first-principle calculations. The phonon eigenvectors were found to be highly comparable to those of lead titanate (PbTiO3), and significant splitting of the B-1+E modes was observed in the supertetragonal phase.
JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS
(2023)
Article
Crystallography
Goncalo N. P. Oliveira, Pedro R. Rodrigues, Joao G. Correia, Joao P. E. Araujo, Armandina M. L. Lopes
Summary: In this study, the importance of local distortions in perovskite-like orthochromites for their exhibited properties was investigated through structural and DC magnetisation measurements combined with local probe studies in polycrystalline ErCrO3. The evolution of electric field gradient (EFG) parameters with temperature showed two clear signals of local environment changes, one at the ferroelectric phase transition (T-FE) and the other below 250 K. The observed changes in EFG and the development of a magnetic hyperfine field (MHF) at around 250 K were consistent with the magnetisation measurements, which showed a relatively strong coercive field well above the Cr sub-lattice ordering temperature.
Article
Chemistry, Applied
Renata Matos, Iwona Kuzniarska-Biernacka, Mariana Rocha, Joao H. Belo, Joao Pedro Araujo, Ana C. Estrada, Joana L. Lopes, Tushti Shah, Brian A. Korgel, Clara Pereira, Tito Trindade, Cristina Freire
Summary: This study presents the preparation and characterization of nanocomposites of graphene flakes (GF) combined with CuS, Fe3O4, and CuS-Fe3O4. The adsorption and photocatalytic properties of the nanocomposites were evaluated using Rhodamine B (RhB) as the model contaminant. The results showed successful attachment of CuS and/or Fe3O4 nanoparticles onto GF. The GF@CuS-Fe3O4 nanocomposite exhibited the highest RhB adsorption efficiency and photocatalytic activity, completely eliminating the dissolved RhB after 60 minutes of irradiation.
Article
Chemistry, Physical
B. G. F. Eggert, J. F. H. Belo, J. P. Araujo, B. C. Hauback, C. Frommen
Summary: A series of Mn1-xNi1-xFe2xSi0.95Al0.05 MM'X-type compounds were investigated as potential magnetocaloric materials. The martensitic transition temperatures of the compounds were adjusted by double substitution of Fe in Mn and Ni sites. The isothermal entropy changes were calculated and found to be comparable to those of similar MnNi(SiAl)-based compounds. High magnetic fields were found to be necessary for inducing the magnetostructural transition due to the presence of secondary phases and/or disorder.
Article
Physics, Applied
Rui M. Costa, Edmund Lovell, R. Almeida, R. M. C. Pinto, Lesley F. Cohen, A. M. Pereira, Joao P. Araujo, J. H. Belo
Summary: The magnetocaloric effect is largest near a first-order phase transition and can be used in magnetocaloric refrigeration, eliminating the need for greenhouse gases. However, this transition is accompanied by hysteresis and unique dynamical effects, which can be detrimental for refrigeration applications.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2023)
Article
Polymer Science
Fernanda R. Vieira, Nuno V. Gama, Dmitry V. Evtuguin, Carlos O. Amorim, Vitor S. Amaral, Paula C. O. R. Pinto, Ana Barros-Timmons
Summary: Rigid polyurethane foams (RPUFs) were synthesized using lignin-based polyol obtained through the reaction of kraft lignin with propylene carbonate. The formulations were optimized to achieve low thermal conductivity and low density for lightweight insulation. The resulting bio-based RPUFs exhibited comparable properties to commercial RPUFs and showed potential as a replacement for petroleum-based RPUFs. This study introduces a novel approach using 100% unpurified lignin-based polyol in the production of RPUFs.
Article
Chemistry, Multidisciplinary
Sara C. Freitas, Joao H. Belo, Andreia Granja, Miguel Canhota, Ana S. Silva, Salette Reis, Helder Crespo, Joao P. Araujo, Celia T. Sousa
Summary: This study systematically investigated the heating performance of gold nanorods under near-infrared radiation and evaluated the influence of nanorods concentration, total volume, laser output power, and spot area. The experimental results showed that the lowest concentration of nanorods (24 μg/mL) exhibited the most promising heating results, with a Specific Absorption Rate (SAR) value of 24.6 kW/g(Au) under the highest laser power, spot area, and volume conditions. Laser output power and concentration were identified as the key parameters for the global heating of the sample.
ADVANCED MATERIALS INTERFACES
(2023)
Article
Chemistry, Multidisciplinary
Ana Rita F. Pacheco, Beatriz D. Cardoso, Ana Pires, Andre M. Pereira, Joao P. Araujo, Violeta M. Carvalho, Raquel O. Rodrigues, Paulo J. G. Coutinho, Teresa Castelo-Grande, Paulo A. Augusto, Domingos Barbosa, Rui A. Lima, Senhorinha F. C. F. Teixeira, Ana Rita O. Rodrigues, Elisabete M. S. Castanheira
Summary: Late diagnosis and systemic toxicity associated with conventional treatments pose challenges in cancer therapy. Nanomedicine offers a new approach for prevention, diagnosis, and treatment of cancer. This study developed pH-sensitive solid magnetoliposomes (SMLs) for controlled release of the chemotherapeutic drug doxorubicin (DOX). The SMLs showed efficient drug release at pH = 5 and significantly reduced cell viability when exposed to tumor cells, suggesting their potential for synergistic cancer therapy with magnetic targeting and dual hyperthermia.
Article
Materials Science, Multidisciplinary
Maria J. Pereira, Tiago Santos, Rafael Correia, Joao S. Amaral, Vitor S. Amaral, Simone Fabbrici, Franca Albertini
Summary: An innovative study of the magnetocaloric effect (MCE) was conducted using infrared thermography on a Co-doped Ni-Mn-Ga bulk sample with microscopic resolution. MCE maps were created for different sample temperatures, revealing spatially heterogeneous behavior during heating and cooling processes. Significant differences were observed between heating and cooling, with greater amplitude and inhomogeneity on heating. The study also identified varying temperatures and magnitudes of the structural transformation occurring in different micro-regions.
JOURNAL OF PHYSICS-MATERIALS
(2023)
Article
Polymer Science
Silvia D. Martinho, Virginia Cruz Fernandes, Sonia A. Figueiredo, Rui Vilarinho, J. Agostinho Moreira, Cristina Delerue-Matos
Summary: This study simulated the aging process of six types of microplastics in freshwater and seawater ecosystems and evaluated the effects using various analysis methods. The results showed that aging caused changes in the surface characteristics of microplastics and their interaction with other pollutants.
Article
Materials Science, Multidisciplinary
Rui Pinho, Rui Vilarinho, J. Agostinho Moreira, Fatima Zorro, Paulo Ferreira, Maxim Ivanov, Alexander Tkach, M. Elisabete Costa, Paula M. Vilarinho
Summary: The impact of stress on the performance of lead-free potassium sodium niobate (KNN) thin films was investigated. It was found that films with compressive residual stress showed the lowest dielectric losses, highest electric permittivity, and maximum electric polarization. On the other hand, films with tensile residual stress exhibited the smallest polarization and almost negligible out-of-plane piezoresponse. These findings are important for understanding lead-free ferroelectric/piezoelectric behavior and its potential applications.
JOURNAL OF MATERIALS CHEMISTRY C
(2023)
Article
Chemistry, Multidisciplinary
Ana Cristina Rodrigues, Ligia Costa, Ricardo Silva-Carvalho, Renato Mota, Sara Duarte-Silva, Andreia Teixeira-Castro, Nuno Lamas, Goncalo N. P. Oliveira, Yizao Wan, Fernando Dourado, Miguel Gama
Summary: In this study, it was found that BNC nanofibers are not absorbed at the intestine after oral administration in Wistar rats, suggesting that BNC can be considered a safe food additive.
ENVIRONMENTAL SCIENCE-NANO
(2023)
Article
Materials Science, Multidisciplinary
R. Vilarinho, R. C. Vilao, H. Alberto, A. G. Marinopoulos, J. M. Gil, H. Luetkens, Z. Guguchia, M. Mihalik, M. Mihalik Jr, J. Agostinho Moreira
Summary: This study presents a comprehensive investigation into the spin dynamics and fluctuations in the ordered magnetic phases of the prototypical multiferroic material TbMnO3. Strong local magnetic-field disorder arising from the modulated Mn3+ spin arrangement and the effect of Tb3+ ordering at low temperatures is demonstrated through the temperature dependence of the dynamical and static components of the asymmetry. Evidence for an unusual magnetostructural coupling in the paramagnetic phase of TbMnO3 is provided using muon spin spectroscopy. The temperature dependence of the magnetic susceptibility in the paramagnetic phase is attributed to this magnetostructural coupling, likely involving oxygen displacements.
Article
Materials Science, Multidisciplinary
A. Maia, R. Vilarinho, C. Kadlec, M. Lebeda, M. Mihalik Jr, M. Zentkova, M. Mihalik, J. Agostinho Moreira, S. Kamba
Summary: We conducted a comprehensive study on the effect of low-level substitution of Mn3+ by Fe3+ on the magnetoelectric coupling in TbMn1-xFexO3. The substitution of cations has a significant impact on the stability of magnetic structures and ferroelectric phase at low temperatures. Different mechanisms for static and dynamic magnetoelectric coupling were observed. Our findings also reveal the existence of spin-phonon coupling in pure TbMnO3, which increases with Fe concentration.
