Physical Review Materials最新文献

{"title":"Generalizing the structural phase field crystal approach for modeling solid-liquid-vapor phase transformations in pure materials","authors":"Daniel L. Coelho, Duncan Burns, Emily Wilson, Nikolas Provatas","doi":"10.1103/physrevmaterials.8.093402","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.093402","url":null,"abstract":"In a recent class of phase field crystal (PFC) models, the density order parameter is coupled to powers of its mean field. This effectively introduces a phenomenology of higher-order direct correlation functions acting on long wavelengths, which is required for modeling solid-liquid-vapor systems. The present work generalizes these models by incorporating, into a single-field theory, higher-order direct correlations, systematically constructed in reciprocal space to operate across long <i>and</i> short wavelengths. The correlation kernels introduced are also readily adaptable to describe distinct crystal structures. We examine the three-phase equilibrium properties and phase diagrams of the proposed model, and reproduce parts of the aluminum phase diagram as an example of its versatile parametrization. We assess the dynamics of the model, showing that it allows robust control of the interface energy between the vapor and condensed phases (liquid and solid). We also examine the dynamics of solid-vapor interfaces over a wide range of parameters and find that dynamical artifacts reported in previous PFC models do not occur in the present formalism. Additionally, we demonstrate the capacity of the proposed formalism for computing complex microstructures and defects such as dislocations, grain boundaries, and voids in solid-liquid-vapor systems, all of which are expected to be crucial for investigating rapid solidification processes.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206099","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Deposition of highly crystalline AlScN thin films using synchronized high-power impulse magnetron sputtering: From combinatorial screening to piezoelectric devices","authors":"Jyotish Patidar, Kerstin Thorwarth, Thorsten Schmitz-Kempen, Roland Kessels, Sebastian Siol","doi":"10.1103/physrevmaterials.8.095001","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.095001","url":null,"abstract":"With the integration of 5G in day-to-day devices and the foreseeable 6G revolution, demand for advanced radio frequency (RF) microelectromechanical systems (MEMS) is growing. Aluminum scandium nitride (AlScN) has emerged as the material of choice for many of those applications due to its superior piezoelectric and electromechanical properties compared to aluminum nitride (AlN). However, synthesizing high-quality, textured AlScN thin films is challenging. Alloying of Sc in AlN induces structural frustration leading to strain, defects, disoriented grains, and disrupted crystal symmetry during growth. Higher deposition temperatures, while improving crystalline quality, risk undesirable phase precipitation and limit industrial sustainability. In addition, future MEMS technologies also demand conformal and textured coatings over diverse topographies. Addressing these challenges collectively requires new and innovative synthesis approaches. In this study, we investigate the feasibility of ionized physical vapor deposition to deposit highly oriented AlScN films with minimal defects at lower temperatures. To this end, we employ combinations of different deposition approaches, such as metal-ion synchronized (MIS) high-power impulse magnetron sputtering (HiPIMS). Leveraging the high ionization rates of HiPIMS and optimally timed substrate bias potentials, we selectively bombard the growing film with Al and/or Sc ions to enhance the adatom mobility at low temperatures while simultaneously providing the ability to tune stress and coat complex structures conformally. The nonequilibrium solubility of Sc in wurtzite AlN under different conditions is investigated using a combinatorial deposition approach. Promising candidates with <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mo>∼</mo><mn>20</mn><mo>%</mo></mrow></math> Sc composition are isolated and characterized for crystallinity and residual stress. Disoriented grains, a significant issue in growing AlScN films, are observed through atomic force microscopy and found to be completely removed by substrate rotation and application of substrate biasing. The measured piezoelectric response of the films with approximately 20% Sc concentration ranges from 6.3 to 8.8 <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>pm</mi><mo>/</mo><mi mathvariant=\"normal\">V</mi></mrow></math>, in line with density functional theory predictions and experimentally reported values for films deposited in a production tool with coplanar geometry. At the same time, MIS-HiPIMS-deposited films offer unique properties and flexibility to tune their stress state and structural properties, thus presenting exciting opportunities for the fabrication of advanced RF filters and next-generation MEMS devices.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206100","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Atomic-structure changes of 30∘ partial-dislocation cores due to excess carriers in GaP","authors":"Sena Hoshino, Shuji Oi, Yu Ogura, Tatsuya Yokoi, Yan Li, Atsutomo Nakamura, Katsuyuki Matsunaga","doi":"10.1103/physrevmaterials.8.093605","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.093605","url":null,"abstract":"It was experimentally reported that light illumination leads to reduced deformation stresses in some III-V compound semiconductors such as GaP. This phenomenon is known as the negative photoplastic effect, which is expected to originate from interactions between photoexcited carriers and glide dislocations. To clarify its physical origin at the atomic and electronic levels, density-functional-theory calculations were performed for Shockley <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mn>30</mn><mo>∘</mo></msup></math> partial dislocations in GaP. In the absence of excess carriers, both Ga and P cores of the partial dislocations were found to have reconstructed structures that are energetically most stable. This can be understood by the fact that dangling-bond-like states at undercoordinated atoms of the dislocation cores are removed by core reconstruction. In the presence of excess carriers that would be formed by light illumination, the reconstructed Ga and P cores were able to trap excess holes and electrons, respectively, and were subsequently transformed to unreconstructed structures. It was also found that the unreconstructed structures due to excess carriers tend to have smaller potential barrier heights for dislocation glide, as compared to the pristine reconstructed structures without any excess carriers. This is in good agreement with the increased dislocation mobility in GaP under external light illumination that has been experimentally reported.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206101","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tc and resistivity variation induced by external bending strain in flexible film of strain-sensitive (La,Sr)2CuO4","authors":"Tomoya Horide, Tomoaki Maekawa, Tatsuro Aikawa, Takanori Kitamura, Kazuma Nakamura","doi":"10.1103/physrevmaterials.8.094802","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.094802","url":null,"abstract":"Strain in materials changes their electronic structure, and the strain response realizes rich material properties and devices. Superconductivity under hydrostatic pressure and epitaxial strain suggests significant response to an external variable strain in a single sample, but this has not yet been demonstrated because the strain is usually a fixed parameter after sample fabrication. <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mrow><mo>(</mo><mrow><mi>La</mi><mo>,</mo><mi>Sr</mi></mrow><mo>)</mo></mrow><mn>2</mn></msub><mi>Cu</mi><msub><mi mathvariant=\"normal\">O</mi><mn>4</mn></msub></mrow></math> films were fabricated on flexible metal substrates, and bending strain was applied to them to observe the critical temperature <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mo>(</mo><msub><mi>T</mi><mi mathvariant=\"normal\">c</mi></msub><mo>)</mo></mrow></math> and resistivity variation induced by strain. The compressive bending strain of −0.005 increased the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>T</mi><mi mathvariant=\"normal\">c</mi></msub></math> from 23.4 to 27.3 K. The magnitude of the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>T</mi><mi mathvariant=\"normal\">c</mi></msub></math> change by the bending strain is independent of the doping level and initial epitaxial strain. Furthermore, the irreversibility temperature was also improved by the compressive bending, and reasonable <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>T</mi><mi mathvariant=\"normal\">c</mi></msub></math> variation with respect to the reversible strain was observed. <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>A</mi></mrow></math><i>b initio</i> density functional calculation for the mother compound <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi mathvariant=\"normal\">L</mi><msub><mi mathvariant=\"normal\">a</mi><mn>2</mn></msub><mi>Cu</mi><msub><mi mathvariant=\"normal\">O</mi><mn>4</mn></msub></mrow></math> clarified that the low-energy electronic structures are sensitive to the bending strain. While the carriers (holes) are preferentially injected into the in-plane orbitals of the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>Cu</mi><msub><mi mathvariant=\"normal\">O</mi><mn>2</mn></msub></mrow></math> plane under the compressive strain, the tensile strain leads to the carrier injection into the perpendicular orbitals which is unfavorable to the superconductivity. The strain-sensitive high-<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>T</mi><mi mathvariant=\"normal\">c</mi></msub></math> superconductor under the external strain highlights a new aspect for cuprate superconductors, which opens monitoring of the stress situation in the cryogenic systems such as superconducting magnet and liquid hydrogen container.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206103","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Accuracy of metaGGA functionals in describing transition metal fluorides","authors":"Dereje Bekele Tekliye, Gopalakrishnan Sai Gautam","doi":"10.1103/physrevmaterials.8.093801","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.093801","url":null,"abstract":"Accurate predictions of material properties within the chemical space of transition metal fluorides (TMFs), using computational frameworks such as density functional theory (DFT), is important for advancing several technological applications. The state-of-the-art semilocal exchange-correlation functionals within DFT include the strongly constrained and appropriately normed (SCAN) and the restored regularized SCAN (&lt;math xmlns=\"http://www.w3.org/1998/Math/MathML\"&gt;&lt;mrow&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi mathvariant=\"normal\"&gt;r&lt;/mi&gt;&lt;/mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/msup&gt;&lt;mi&gt;SCAN&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;), both of which are meta generalized gradient approximation (metaGGA) functionals. Given their semilocal nature, both SCAN and &lt;math xmlns=\"http://www.w3.org/1998/Math/MathML\"&gt;&lt;mrow&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi mathvariant=\"normal\"&gt;r&lt;/mi&gt;&lt;/mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/msup&gt;&lt;mi&gt;SCAN&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt; are susceptible to self-interaction errors (SIEs) while modeling highly correlated &lt;math xmlns=\"http://www.w3.org/1998/Math/MathML\"&gt;&lt;mi&gt;d&lt;/mi&gt;&lt;/math&gt; electrons of transition metals. Hence, in this work, we evaluate the accuracy of both SCAN and &lt;math xmlns=\"http://www.w3.org/1998/Math/MathML\"&gt;&lt;mrow&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi mathvariant=\"normal\"&gt;r&lt;/mi&gt;&lt;/mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/msup&gt;&lt;mi&gt;SCAN&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt; functionals in estimating several properties of TMFs, including redox enthalpies, lattice geometries, on-site magnetic moments, and band gaps. Specifically, we consider binary fluorides of Ti, V, Cr, Mn, Fe, Co, Ni, and Cu. We observe both SCAN and &lt;math xmlns=\"http://www.w3.org/1998/Math/MathML\"&gt;&lt;mrow&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi mathvariant=\"normal\"&gt;r&lt;/mi&gt;&lt;/mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/msup&gt;&lt;mi&gt;SCAN&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt; exhibit poor accuracy in estimating fluorination enthalpies among TMFs, which can be primarily attributed to SIEs among the &lt;math xmlns=\"http://www.w3.org/1998/Math/MathML\"&gt;&lt;mi&gt;d&lt;/mi&gt;&lt;/math&gt; electrons, given both functionals bind &lt;math xmlns=\"http://www.w3.org/1998/Math/MathML\"&gt;&lt;msub&gt;&lt;mi mathvariant=\"normal\"&gt;F&lt;/mi&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt;&lt;/math&gt; accurately. Thus, we derive optimal Hubbard &lt;math xmlns=\"http://www.w3.org/1998/Math/MathML\"&gt;&lt;mrow&gt;&lt;mi&gt;U&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt; corrections for both functionals based on experimental fluorination (or oxidation) enthalpies within binary TMFs. Note that our attempts at using the linear response theory to derive &lt;math xmlns=\"http://www.w3.org/1998/Math/MathML\"&gt;&lt;mrow&gt;&lt;mi&gt;U&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt; corrections yielded unphysical values for V, Fe, and Ni fluorides. While adding the fluorination-enthalpy-derived &lt;math xmlns=\"http://www.w3.org/1998/Math/MathML\"&gt;&lt;mrow&gt;&lt;mi&gt;U&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt; corrections to the metaGGA functionals does not significantly affect the lattice volumes and on-site magnetic moments (and in turn, the accuracy of these property estimations versus experiments), it does cause a significant increase in calculated band gaps. Note that the &lt;math xmlns=\"http://www.w3.org/1998/Math/MathML\"&gt;&lt;mrow&gt;&lt;mi&gt;U&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;-corrected band gaps in several fluorides deviate to a lesser extent from band gaps calc","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206102","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Giant spin splitting and its origin in methylhydrazinium lead halide perovskites","authors":"Nikhilesh Maity, Ravi Kashikar, S. Lisenkov, I. Ponomareva","doi":"10.1103/physrevmaterials.8.l091402","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.l091402","url":null,"abstract":"Spin splitting, or removal of spin degeneracy in the electronic energy band/level, is often a measure of spin-orbit coupling strength and a way to manipulate spin degrees of freedom. We use first-principles simulations to predict giant spin splitting in methylhydrazinium lead halide (<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>MHyPbX</mi><mn>3</mn></msub><mo>,</mo><mo> </mo><mrow><mi>MHy</mi><mo>=</mo><msub><mi>CH</mi><mn>3</mn></msub><msub><mi>NH</mi><mn>2</mn></msub><msub><mi>NH</mi><mn>2</mn></msub></mrow><mo>,</mo><mo> </mo><mrow><mi>X</mi></mrow></math> = Br and Cl) hybrid organic-inorganic perovskites. The values can reach up to 408.0 meV at zero Kelvin and 281.6 meV at room temperature. The origin of the effect is traced to the large distortion of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>PbX</mi><mn>3</mn></msub></math> framework, driven primarily by Pb ions in the ferroelectric <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mi mathvariant=\"normal\">Γ</mi><mrow><mn>3</mn><mo>−</mo></mrow></msup></math> mode. The Pb displacements consist of a combination of polar and antipolar arrangements and result in up to 39.2 meV/atom enhancement of the spin-orbit coupling energy in the polar phase of the materials. The spin-orbit coupling gives origin to persistent spin textures in <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>MHyPbX</mi><mn>3</mn></msub></math>, which are desirable for applications in spintronics and quantum computing. Our findings reveal an additional functionality for hybrid organic-inorganic perovskite and open a way for the design of more materials with giant spin splitting.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206104","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Core structure of dislocations in ordered ferromagnetic FeCo","authors":"Aleksei Egorov, Antoine Kraych, Matous Mrovec, Ralf Drautz, Thomas Hammerschmidt","doi":"10.1103/physrevmaterials.8.093604","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.093604","url":null,"abstract":"We elucidated the core structure of screw dislocations in ordered B2 FeCo using a recent magnetic bond-order potential (BOP) [Egorov <i>et al.</i>, <span>Phys. Rev. Mater.</span> <b>7</b>, 044403 (2023)]. We corroborated that dislocations in B2 FeCo exist in pairs separated by antiphase boundaries. The equilibrium separation is about 50 Å, which demands large-scale atomistic simulations—inaccessible for density functional theory but attainable with BOP. We performed atomistic simulations of these separated dislocations with BOP and predicted that they reside in degenerate core structures. Additionally, dislocations induce changes in the local electronic structure and magnetic moments.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206113","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Direct evidence for carbon incorporation on the nitrogen site in AlN","authors":"Darshana Wickramaratne, Mackenzie Siford, Md Shafiqul Islam Mollik, John L. Lyons, M. E. Zvanut","doi":"10.1103/physrevmaterials.8.094602","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.094602","url":null,"abstract":"We use photo-electron paramagnetic resonance (EPR) measurements and first-principles calculations to identify and explain the properties of carbon in AlN. We present clear evidence for carbon substitution on the nitrogen site (<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi mathvariant=\"normal\">C</mi><mi mathvariant=\"normal\">N</mi></msub></math>). We also clarify the origin of a widely observed EPR spectra in AlN that, although often attributed to a deep donor defect, we demonstrate is surprisingly due to <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi mathvariant=\"normal\">C</mi><mi mathvariant=\"normal\">N</mi></msub></math>. Finally, we show the presence of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi mathvariant=\"normal\">C</mi><mi mathvariant=\"normal\">N</mi></msub></math> is consistent with the absorption spectra at 4.7 eV observed in AlN.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206106","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"First-principles study of the order-disorder transition in the AlCrTiV high entropy alloy","authors":"Michael Widom","doi":"10.1103/physrevmaterials.8.093603","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.093603","url":null,"abstract":"The AlCrTiV high entropy alloy undergoes an order-disorder transition from body-centered cubic (Strukturbericht A2) at high temperatures to the CsCl structure (B2) at intermediate temperatures. We model this transition using first principles Monte Carlo/molecular dynamics simulations. Simulation results yield the temperature-dependent energy, entropy, heat capacity, occupancy fluctuations, and diffraction patterns. The contribution of chemical disorder to the entropy is calculated on the basis of point and pair cluster frequencies. The simulated structures exhibit compensated ferrimagnetism, and the Fermi level lies in a pseudogap. Sensitivity of structure and magnetism to the exchange-correlation functional is discussed, and neutron diffraction experiments are proposed to help resolve the true chemical order.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206105","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Magnetic properties of the quasi-XY Shastry-Sutherland magnet Er2Be2SiO7","authors":"A. Brassington, Q. Ma, G. Sala, A. I. Kolesnikov, K. M. Taddei, Y. Wu, E. S. Choi, H. Wang, W. Xie, J. Ma, H. D. Zhou, A. A. Aczel","doi":"10.1103/physrevmaterials.8.094001","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.094001","url":null,"abstract":"Polycrystalline and single-crystal samples of the insulating Shastry-Sutherland compound <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Er</mi><mn>2</mn></msub><msub><mi>Be</mi><mn>2</mn></msub><msub><mi>SiO</mi><mn>7</mn></msub></mrow></math> were synthesized via a solid-state reaction and the floating zone method, respectively. The crystal structure, Er single-ion anisotropy, zero-field magnetic ground state, and magnetic phase diagrams along high-symmetry crystallographic directions were investigated with bulk measurement techniques, x-ray and neutron diffraction, and neutron spectroscopy. We establish that <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Er</mi><mn>2</mn></msub><msub><mi>Be</mi><mn>2</mn></msub><msub><mi>SiO</mi><mn>7</mn></msub></mrow></math> crystallizes in a tetragonal space group with planes of orthogonal Er dimers and a strong preference for the Er moments to lie in the local plane perpendicular to each dimer bond. We also find that this system has a noncollinear ordered ground state in zero field with a transition temperature of 0.841 K consisting of antiferromagnetic dimers and in-plane moments. Finally, we mapped out the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>H</mi><mtext>−</mtext><mi>T</mi></mrow></math> phase diagrams for <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Er</mi><mn>2</mn></msub><msub><mi>Be</mi><mn>2</mn></msub><msub><mi>SiO</mi><mn>7</mn></msub></mrow></math> along the directions <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>H</mi><mo>∥</mo></mrow></math> [001], [100], and [110]. While an increasing in-plane field simply induces a phase transition to a field-polarized phase, we identify three metamagnetic transitions in the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>H</mi><mo>∥</mo></mrow></math> [001] case. Single-crystal neutron diffraction results reveal that the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>H</mi><mo>∥</mo></mrow></math> [001] phase diagram can be explained predominantly by the expected field-induced behavior of classical, anisotropic moments, although the microscopic origin of one phase requires further investigation.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206107","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}