Pub Date : 2024-10-02DOI: 10.1016/j.physb.2024.416592
The as-prepared Mn0.5Zn0.5Ni0.5Fe1.5O4 ferrite was prepared by the co-precipitation process and annealed at 300, 500, 900, and 1100 °C. The single-phase cubic spinel structure was confirmed by XRD patterns, Rietveld fitting, TEM imaging and several structural parameters, including crystalline size and lattice constant have been examined. The FTIR spectrum confirmed the main two absorption bands of tetrahedral and octahedral sites in ferrite, where the elastic parameters such as force constants and Debye temperature have been investigated. The saturation magnetization increases with the annealing temperature, while the energy band gap decreases with the annealing temperature, and also the ac conductivity decreases with annealing temperature.
通过共沉淀工艺制备了 Mn0.5Zn0.5Ni0.5Fe1.5O4 铁氧体，并在 300、500、900 和 1100 °C 下进行了退火处理。通过 XRD 图谱、里特维尔德拟合和 TEM 成像确认了单相立方尖晶石结构，并检测了多个结构参数，包括晶体尺寸和晶格常数。傅立叶变换红外光谱证实了铁氧体中四面体和八面体位点的两个主要吸收带，并对力常数和德拜温度等弹性参数进行了研究。饱和磁化率随退火温度的升高而升高，能带隙随退火温度的升高而减小，交流电导率随退火温度的升高而减小。
{"title":"Tunable annealing temperature for the structural, magnetic, optical, and dielectric characteristics of Mn0.5Zn0.5Ni0.5Fe1.5O4 nano-ferrite","authors":"","doi":"10.1016/j.physb.2024.416592","DOIUrl":"10.1016/j.physb.2024.416592","url":null,"abstract":"<div><div>The as-prepared Mn<sub>0.5</sub>Zn<sub>0.5</sub>Ni<sub>0.5</sub>Fe<sub>1.5</sub>O<sub>4</sub> ferrite was prepared by the co-precipitation process and annealed at 300, 500, 900, and 1100 °C. The single-phase cubic spinel structure was confirmed by XRD patterns, Rietveld fitting, TEM imaging and several structural parameters, including crystalline size and lattice constant have been examined. The FTIR spectrum confirmed the main two absorption bands of tetrahedral and octahedral sites in ferrite, where the elastic parameters such as force constants and Debye temperature have been investigated. The saturation magnetization increases with the annealing temperature, while the energy band gap decreases with the annealing temperature, and also the ac conductivity decreases with annealing temperature.</div></div>","PeriodicalId":20116,"journal":{"name":"Physica B-condensed Matter","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419203","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-01DOI: 10.1016/j.physb.2024.416585
A theoretical study is presented on the amplification of surface acoustic waves (SAWs) due to their interaction with conduction electrons in gate voltage-controlled bilayer graphene (BLG) in the presence of a dc electric field applied to the BLG sample. Using the Green’s function method, the SAW gain is calculated depending on the density of conduction electrons and the band gap in the electronic spectrum of BLG. It is found that the bias voltage-induced band gap opening in BLG significantly increases the SAW gain, which can be almost four times that of unbiased BLG at room temperature, provided the electron density is not too high ( cm−2). The theory developed also shows that the electron density dependence of the SAW gain is non-monotonic: as the electron density increases from to cm−2, the gain first increases, reaching a maximum, and then decreases.
{"title":"Amplification of surface acoustic waves through interaction with drifting conduction electrons in gate voltage-controlled bilayer graphene","authors":"","doi":"10.1016/j.physb.2024.416585","DOIUrl":"10.1016/j.physb.2024.416585","url":null,"abstract":"<div><div>A theoretical study is presented on the amplification of surface acoustic waves (SAWs) due to their interaction with conduction electrons in gate voltage-controlled bilayer graphene (BLG) in the presence of a dc electric field applied to the BLG sample. Using the Green’s function method, the SAW gain is calculated depending on the density of conduction electrons and the band gap in the electronic spectrum of BLG. It is found that the bias voltage-induced band gap opening in BLG significantly increases the SAW gain, which can be almost four times that of unbiased BLG at room temperature, provided the electron density is not too high (<span><math><mrow><mo>≲</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>12</mn></mrow></msup></mrow></math></span> cm<sup>−2</sup>). The theory developed also shows that the electron density dependence of the SAW gain is non-monotonic: as the electron density increases from <span><math><mrow><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>11</mn></mrow></msup></mrow></math></span> to <span><math><mrow><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>13</mn></mrow></msup></mrow></math></span> cm<sup>−2</sup>, the gain first increases, reaching a maximum, and then decreases.</div></div>","PeriodicalId":20116,"journal":{"name":"Physica B-condensed Matter","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419231","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-01DOI: 10.1016/j.physb.2024.416591
This paper reveals the mechanism of Hf and Ti doping promoting hydrogen release in ZrCoH3. Different from previous experimental methods, this study employs the plane wave pseudopotential method and density functional theory to predict the relationship between the formation energy and electronic structure of the ZrCoH3-Hf/Ti system, and uses theoretical calculations to guide the modification design of ZrCoH3. Firstly, by calculating the thermodynamic properties of the ZrCoH3-Hf/Ti system and combining the density of states theory, the bonding characteristics and dehydrogenation preference between H atoms and neighboring metal atoms in the ZrCoH3-Hf/Ti system are determined. Additionally, the electronic structure of the ZrCoH3-Hf/Ti system is calculated to elucidate the hybridization of bonding and antibonding orbitals between atoms in the ZrCoH3-Hf/Ti system. Moreover, DCo-d is utilized to measure the strength of antibonding interactions in the ZrCoH3-Hf/Ti system. The main cause of antibonding interactions in the ZrCoH3-Hf/Ti system is attributed to the variation in formation energy, and the change in antibonding interactions is sensitive to the variation in formation energy. Finally, a feasible method to improve the properties of ZrCoH3 is proposed, which involves modifying the electronic structure to increase the partial density of states at the Fermi energy level, making the formation energy of hydrides less negative and forcing the structure to be more unstable. This method has potential application value in the modification of ZrCoH3.
{"title":"First-principles study on the mechanism of Hf and Ti doping promoting hydrogen release in ZrCoH3","authors":"","doi":"10.1016/j.physb.2024.416591","DOIUrl":"10.1016/j.physb.2024.416591","url":null,"abstract":"<div><div>This paper reveals the mechanism of Hf and Ti doping promoting hydrogen release in ZrCoH<sub>3</sub>. Different from previous experimental methods, this study employs the plane wave pseudopotential method and density functional theory to predict the relationship between the formation energy and electronic structure of the ZrCoH<sub>3</sub>-Hf/Ti system, and uses theoretical calculations to guide the modification design of ZrCoH<sub>3</sub>. Firstly, by calculating the thermodynamic properties of the ZrCoH<sub>3</sub>-Hf/Ti system and combining the density of states theory, the bonding characteristics and dehydrogenation preference between H atoms and neighboring metal atoms in the ZrCoH<sub>3</sub>-Hf/Ti system are determined. Additionally, the electronic structure of the ZrCoH<sub>3</sub>-Hf/Ti system is calculated to elucidate the hybridization of bonding and antibonding orbitals between atoms in the ZrCoH<sub>3</sub>-Hf/Ti system. Moreover, D<sub>Co-d</sub> is utilized to measure the strength of antibonding interactions in the ZrCoH<sub>3</sub>-Hf/Ti system. The main cause of antibonding interactions in the ZrCoH<sub>3</sub>-Hf/Ti system is attributed to the variation in formation energy, and the change in antibonding interactions is sensitive to the variation in formation energy. Finally, a feasible method to improve the properties of ZrCoH<sub>3</sub> is proposed, which involves modifying the electronic structure to increase the partial density of states at the Fermi energy level, making the formation energy of hydrides less negative and forcing the structure to be more unstable. This method has potential application value in the modification of ZrCoH<sub>3</sub>.</div></div>","PeriodicalId":20116,"journal":{"name":"Physica B-condensed Matter","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419199","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-30DOI: 10.1016/j.physb.2024.416586
Using the first-principles calculations, we investigate the electronic and magnetic properties of armchair silicon carbide nanoribbon (aSiCNR) with different combinations of edge dual-hydrogenation. The dual-hydrogenation on the boundary Si or C atom changes it from sp2 hybridization to sp3 hybridization, which will have an important role on the stability of aSiCNR. Only the full dual-hydrogenation on the one edge or two edges don't change the band structure and magnetic moment of aSiCNR. However, the other different combinations of edge dual-hydrogenation can result in aSiCNR exhibiting metallic, semiconductor, and half-metallic properties under non-magnetism state, ferromagnetic and anti-ferromagnetic states. These results may present a new avenue for band engineering of aSiCNR, as well as valuable suggestions for the practical application of SiC based nanomaterials in spintronics and multifunctional nanodevices.
我们利用第一性原理计算，研究了不同边缘双氢化组合的臂向碳化硅纳米带（aSiCNR）的电子和磁性能。边界 Si 原子或 C 原子上的双氢化使其从 sp2 杂化变为 sp3 杂化，这将对 aSiCNR 的稳定性产生重要影响。只有单边或双边的完全双氢化不会改变 aSiCNR 的带状结构和磁矩。然而，其他不同的边缘双氢化组合可使 aSiCNR 在非磁态、铁磁态和反铁磁态下表现出金属、半导体和半金属特性。这些结果为 aSiCNR 的能带工程提供了一条新途径，也为 SiC 基纳米材料在自旋电子学和多功能纳米器件中的实际应用提供了宝贵建议。
{"title":"Effect of edge dual-hydrogenation on electronic and magnetic properties of armchair silicon carbide nanoribbons","authors":"","doi":"10.1016/j.physb.2024.416586","DOIUrl":"10.1016/j.physb.2024.416586","url":null,"abstract":"<div><div>Using the first-principles calculations, we investigate the electronic and magnetic properties of armchair silicon carbide nanoribbon (aSiCNR) with different combinations of edge dual-hydrogenation. The dual-hydrogenation on the boundary Si or C atom changes it from <em>sp</em><sup>2</sup> hybridization to <em>sp</em><sup>3</sup> hybridization, which will have an important role on the stability of aSiCNR. Only the full dual-hydrogenation on the one edge or two edges don't change the band structure and magnetic moment of aSiCNR. However, the other different combinations of edge dual-hydrogenation can result in aSiCNR exhibiting metallic, semiconductor, and half-metallic properties under non-magnetism state, ferromagnetic and anti-ferromagnetic states. These results may present a new avenue for band engineering of aSiCNR, as well as valuable suggestions for the practical application of SiC based nanomaterials in spintronics and multifunctional nanodevices.</div></div>","PeriodicalId":20116,"journal":{"name":"Physica B-condensed Matter","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419230","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-30DOI: 10.1016/j.physb.2024.416588
Numerous diverse grown-in point defects in hexagonal boron nitride exhibit properties of single photon emitters stimulating the development of controllable methods for their local formation. In this work the defects created in hexagonal boron nitride by helium ion irradiation were investigated by means of cathodoluminescence and Raman spectroscopy. The irradiation with ion fluence above 1015 cm−2 resulted in a new Raman spectral band at about 1295 cm−1, which can be attributed to the formation of vacancies or divacancies. The intensity of the defect-related luminescence was found to vary non-monotonically with ion fluence and possessed a maximum at about 1014 cm−2. On the basis of this result a new procedure to fabricate light emitting discs by means of the focused helium ion beam was suggested and demonstrated.
{"title":"Tuning luminescence properties of hexagonal boron nitride with focused helium ion beam","authors":"","doi":"10.1016/j.physb.2024.416588","DOIUrl":"10.1016/j.physb.2024.416588","url":null,"abstract":"<div><div>Numerous diverse grown-in point defects in hexagonal boron nitride exhibit properties of single photon emitters stimulating the development of controllable methods for their local formation. In this work the defects created in hexagonal boron nitride by helium ion irradiation were investigated by means of cathodoluminescence and Raman spectroscopy. The irradiation with ion fluence above 10<sup>15</sup> cm<sup>−2</sup> resulted in a new Raman spectral band at about 1295 cm<sup>−1</sup>, which can be attributed to the formation of vacancies or divacancies. The intensity of the defect-related luminescence was found to vary non-monotonically with ion fluence and possessed a maximum at about 10<sup>14</sup> cm<sup>−2</sup>. On the basis of this result a new procedure to fabricate light emitting discs by means of the focused helium ion beam was suggested and demonstrated.</div></div>","PeriodicalId":20116,"journal":{"name":"Physica B-condensed Matter","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419200","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-30DOI: 10.1016/j.physb.2024.416583
Theoretical research has introduced two-dimensional structures of thin sheets known as the pristine C2N monolayer and the Zn-doped C2N monolayer. These sheets show promise as nanocarriers for delivering the anticancer drug purinethol (PU). Through calculations of binding energy (Eb), it was observed that both the pristine C2N monolayer (−0.505 eV) and the Zn-decorated C2N monolayer (−0.762 eV) exhibit favorable characteristics for drug delivery. Eb values fall within range of physisorption, indicating their suitability as candidates for transporting drugs. An observed charge transfer (CT) of 0.035 e occurs in the Zn-decorated C2N monolayer, leading to a depletion of charge in the Zn-doped C2N monolayer system. The primary contributor to this charge loss is the Zn atom, which experiences a charge reduction of 0.035 e. To understand the phenomenon of drug release, the binding energy was recalculated under biological conditions, specifically in an acidic environment. The results indicate a decline in Eb (−0.218 eV) as well as a short recovery time, suggesting successful release of PU within body. The theoretical predictions we have made are expected to serve as inspiration for experimental researchers in their efforts to design drug delivery systems (DDSs) based on C2N monolayers.
{"title":"Assessing pristine and metal doped C2N monolayer as a nanocarriers for anticancer drug","authors":"","doi":"10.1016/j.physb.2024.416583","DOIUrl":"10.1016/j.physb.2024.416583","url":null,"abstract":"<div><div>Theoretical research has introduced two-dimensional structures of thin sheets known as the pristine C<sub>2</sub>N monolayer and the Zn-doped C<sub>2</sub>N monolayer. These sheets show promise as nanocarriers for delivering the anticancer drug purinethol (PU). Through calculations of binding energy (E<sub>b</sub>), it was observed that both the pristine C<sub>2</sub>N monolayer (−0.505 eV) and the Zn-decorated C<sub>2</sub>N monolayer (−0.762 eV) exhibit favorable characteristics for drug delivery. E<sub>b</sub> values fall within range of physisorption, indicating their suitability as candidates for transporting drugs. An observed charge transfer (CT) of 0.035 e occurs in the Zn-decorated C<sub>2</sub>N monolayer, leading to a depletion of charge in the Zn-doped C<sub>2</sub>N monolayer system. The primary contributor to this charge loss is the Zn atom, which experiences a charge reduction of 0.035 e. To understand the phenomenon of drug release, the binding energy was recalculated under biological conditions, specifically in an acidic environment. The results indicate a decline in E<sub>b</sub> (−0.218 eV) as well as a short recovery time, suggesting successful release of PU within body. The theoretical predictions we have made are expected to serve as inspiration for experimental researchers in their efforts to design drug delivery systems (DDSs) based on C<sub>2</sub>N monolayers.</div></div>","PeriodicalId":20116,"journal":{"name":"Physica B-condensed Matter","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419225","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-29DOI: 10.1016/j.physb.2024.416576
In this study, the frequency/voltage dependent profiles of the real/imaginary parts of the complex-dielectric (ε′, ε"), electric-modulus (M′, M"), impedance (Z′, Z"), loss-tangent (tanδ), ac electrical-conductivity (σac) and phase-angle (θ) were investigated in the frequency and voltage ranges of 2kHz/1 MHz and -2V/4V, respectively. The increase in ε′ and ε” values with decreasing frequency is attributed to surface-states (Nss), surface/dipole-polarizations at the diamond-like carbon (DLC)/Si interface. This behavior of ε′ and ε” is known as Maxwell-Wagner type polarization. The M''-V plot has clear peak for each frequency and its position shifts from −0.6V (at 2 kHz) to 1.65V (at 1 MHz) due to the relaxation process and Nss at low-mid frequencies. Values of ε′ and ε” changed from 16.27 to 8.12 and 456.93 to 8.73 for 3V in the range of 2 kHz and 1 MHz, respectively. Therefore, the fabricated Al/DLC/p-Si can be used as an alternative to insulators for further electronic-charging/energy-storage.
{"title":"On a detail examination of frequency and voltage dependence of dielectric, electric modulus, ac conductivity (σac) of the Al/DLC/p-Si structures between 2 kHz and 1 MHz","authors":"","doi":"10.1016/j.physb.2024.416576","DOIUrl":"10.1016/j.physb.2024.416576","url":null,"abstract":"<div><div>In this study, the frequency/voltage dependent profiles of the real/imaginary parts of the complex-dielectric (ε′, ε\"), electric-modulus (M′, M\"), impedance (Z′, Z\"), loss-tangent (tanδ), ac electrical-conductivity (σac) and phase-angle (θ) were investigated in the frequency and voltage ranges of 2kHz/1 MHz and -2V/4V, respectively. The increase in ε′ and ε” values with decreasing frequency is attributed to surface-states (Nss), surface/dipole-polarizations at the diamond-like carbon (DLC)/Si interface. This behavior of ε′ and ε” is known as Maxwell-Wagner type polarization. The M''-V plot has clear peak for each frequency and its position shifts from −0.6V (at 2 kHz) to 1.65V (at 1 MHz) due to the relaxation process and Nss at low-mid frequencies. Values of ε′ and ε” changed from 16.27 to 8.12 and 456.93 to 8.73 for 3V in the range of 2 kHz and 1 MHz, respectively. Therefore, the fabricated Al/DLC/p-Si can be used as an alternative to insulators for further electronic-charging/energy-storage.</div></div>","PeriodicalId":20116,"journal":{"name":"Physica B-condensed Matter","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419227","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-28DOI: 10.1016/j.physb.2024.416580
The properties of the selenide compound Fe7Se8 with a layered crystal structure of the NiAs type are strongly influenced by substitutions and the distribution of vacancies. The Cr-substituted compound Fe6.5Cr0.5Se8 was obtained in single-crystalline form and studied by x-ray diffraction, energy-dispersive x-ray spectroscopy, thermal expansion and magnetization measurements. It was observed that the partial replacement of iron with chromium led to a twofold decrease in spontaneous volume magnetostriction due to changes in competing magnetoelastic contributions to thermal expansion along and perpendicular to the c axis of the crystal. The replacement of iron with chromium slightly decreases the Néel temperature (from 440 to 435 K) and significantly enhances the critical temperature of spin reorientation transition Tsr (from 115 to 160 K), apparently due to a change in the crystal electric field. Below 160 K, the Fe6.5Cr0.5Se crystal is found to exhibit metamagnetic-like behavior of the magnetization when the magnetic field is applied along the c axis. A jump-like change of the magnetization at a critical field up to ∼10 kOe is attributed to the presence of pinning centers of domain walls presumably due the ordering of chromium atoms substituting iron in cationic layers.
具有 NiAs 型层状晶体结构的硒化物 Fe7Se8 的性质受到取代和空位分布的强烈影响。我们获得了单晶形式的铬取代化合物 Fe6.5Cr0.5Se8，并通过 X 射线衍射、能量色散 X 射线光谱、热膨胀和磁化测量对其进行了研究。研究发现，用铬部分替代铁会导致自发体积磁致伸缩降低两倍，这是由于沿晶体 c 轴和垂直于晶体 c 轴的热膨胀的磁弹性竞争贡献发生了变化。用铬替代铁后，奈尔温度略有降低（从 440 K 降至 435 K），而自旋重新定向转变临界温度 Tsr 则显著升高（从 115 K 升至 160 K），这显然是由于晶体电场发生了变化。在 160 K 以下，当磁场沿 c 轴施加时，Fe6.5Cr0.5Se 晶体的磁化表现出类似元磁性。在临界磁场高达 ∼10 kOe 时，磁化率会发生跳跃式变化，这可能是由于在阳离子层中以铬原子取代铁的有序化作用导致了畴壁钉住中心的存在。
{"title":"Thermal expansion, quasi-metamagnetism and spin-reorientation in Fe7Se8 substituted with chromium","authors":"","doi":"10.1016/j.physb.2024.416580","DOIUrl":"10.1016/j.physb.2024.416580","url":null,"abstract":"<div><div>The properties of the selenide compound Fe<sub>7</sub>Se<sub>8</sub> with a layered crystal structure of the NiAs type are strongly influenced by substitutions and the distribution of vacancies. The Cr-substituted compound Fe<sub>6.5</sub>Cr<sub>0.5</sub>Se<sub>8</sub> was obtained in single-crystalline form and studied by x-ray diffraction, energy-dispersive x-ray spectroscopy, thermal expansion and magnetization measurements. It was observed that the partial replacement of iron with chromium led to a twofold decrease in spontaneous volume magnetostriction due to changes in competing magnetoelastic contributions to thermal expansion along and perpendicular to the <em>c</em> axis of the crystal. The replacement of iron with chromium slightly decreases the Néel temperature (from 440 to 435 K) and significantly enhances the critical temperature of spin reorientation transition <em>T</em><sub>sr</sub> (from 115 to 160 K), apparently due to a change in the crystal electric field. Below 160 K, the Fe<sub>6.5</sub>Cr<sub>0.5</sub>Se crystal is found to exhibit metamagnetic-like behavior of the magnetization when the magnetic field is applied along the <em>c</em> axis. A jump-like change of the magnetization at a critical field up to ∼10 kOe is attributed to the presence of pinning centers of domain walls presumably due the ordering of chromium atoms substituting iron in cationic layers.</div></div>","PeriodicalId":20116,"journal":{"name":"Physica B-condensed Matter","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419201","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-28DOI: 10.1016/j.physb.2024.416567
To meet the high energy demand of society, a conversion to renewable energy sources has become essential and energy should be appropriately stored for future use. This has led to the development of energy-storing devices such as supercapacitors (SCs). To enhance capacitive behavior, the concept of quantum capacitance ( is unveiled, which results from the confinement of electrons in their energy states. In this work, 1T phase of MoS2 is studied as it has received a lot of attention because of its wide applications in the energy storage devices and electronics. Here, the electronic structure, and surface charge density (σ) of one, two and three-layered structures of 1T phase is studied using Density Functional Theory. No bandgap is obtained in the Density of States (DOS) and the bands plot of 1T structure indicates their metallic character and the DOS is continuous in all three layers. The of three-layered structure dominates over the other two layers throughout the potential window. The larger and σ values are obtained as 1718.06 μF cm−2 and -1299.50 μC cm−2 for three-layered structure at −0.27 V and −1 V respectively. For analyzing the mechanical strength, Young's modulus is evaluated for optimized structure by applying uni-axial strain. The value is obtained as 177.37 GPa, which is a measure of elastic deformation behavior. The results suggest that the capacitive performance of 1T MoS2 for SC applications is better and it can function as flexible cathode material for asymmetric SC applications.
{"title":"Computational analysis of 1T-MoS2: Probing the interplay of layer-dependent electronic structure, quantum capacitance, charge density and mechanical properties","authors":"","doi":"10.1016/j.physb.2024.416567","DOIUrl":"10.1016/j.physb.2024.416567","url":null,"abstract":"<div><div>To meet the high energy demand of society, a conversion to renewable energy sources has become essential and energy should be appropriately stored for future use. This has led to the development of energy-storing devices such as supercapacitors (SCs). To enhance capacitive behavior, the concept of quantum capacitance (<span><math><mrow><msub><mi>C</mi><mi>Q</mi></msub><mo>)</mo></mrow></math></span> is unveiled, which results from the confinement of electrons in their energy states. In this work, 1T phase of MoS<sub>2</sub> is studied as it has received a lot of attention because of its wide applications in the energy storage devices and electronics. Here, the electronic structure, <span><math><mrow><msub><mi>C</mi><mi>Q</mi></msub></mrow></math></span> and surface charge density (σ) of one, two and three-layered structures of 1T phase is studied using Density Functional Theory. No bandgap is obtained in the Density of States (DOS) and the bands plot of 1T structure indicates their metallic character and the DOS is continuous in all three layers. The <span><math><mrow><msub><mi>C</mi><mi>Q</mi></msub></mrow></math></span> of three-layered structure dominates over the other two layers throughout the potential window. The larger <span><math><mrow><msub><mi>C</mi><mi>Q</mi></msub></mrow></math></span> and σ values are obtained as 1718.06 μF cm<sup>−2</sup> and -1299.50 μC cm<sup>−2</sup> for three-layered structure at −0.27 V and −1 V respectively. For analyzing the mechanical strength, Young's modulus is evaluated for optimized structure by applying uni-axial strain. The value is obtained as 177.37 GPa, which is a measure of elastic deformation behavior. The results suggest that the capacitive performance of 1T MoS<sub>2</sub> for SC applications is better and it can function as flexible cathode material for asymmetric SC applications.</div></div>","PeriodicalId":20116,"journal":{"name":"Physica B-condensed Matter","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419314","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-27DOI: 10.1016/j.physb.2024.416582
In this study, we investigated the ANiSn (A = Ti, Th, U) half-Heusler materials for various properties, including structural, electronic, mechanical, elastic anisotropic, optical, and thermal properties, using Density Functional Theory (DFT) with the Cambridge Serial Total Energy Package (CASTEP) code. The elastic constants satisfied Born's criteria, confirming the thermodynamic and mechanical stability of the ANiSn compounds. Mechanical stability was further assessed through bulk modulus, shear modulus, and Poisson's ratio. Our analysis revealed that TiNiSn and ThNiSn exhibit ductile behaviour, whereas UNiSn is brittle. The calculated elastic modulus indicated that the compounds we studied are elastically anisotropic. The electronic and optical properties confirmed the semiconducting nature of these materials, with significant absorption and conductivity observed in the ultraviolet region. ANiSn is suitable for manufacturing various optoelectronic devices, such as laser diodes (LDs), photodetectors, LEDs, and UV sensors, due to its high absorption coefficient in the IR to UV regions. Additionally, measured Debye and melting temperatures confirmed that TiNiSn is more thermally conductive and can be used in high-temperature structural substances. The low minimum thermal conductivity suggests that UNiSn may be a more efficient material for thermal barrier coatings (TBC) compared to TiNiSn and ThNiSn.
{"title":"Theoretical investigation of structural, mechanical, electronic, optical, and thermal properties of ternary compounds of heusler alloy ANiSn (A= TI, TH, U) using first principles calculations","authors":"","doi":"10.1016/j.physb.2024.416582","DOIUrl":"10.1016/j.physb.2024.416582","url":null,"abstract":"<div><div>In this study, we investigated the ANiSn (A = Ti, Th, U) half-Heusler materials for various properties, including structural, electronic, mechanical, elastic anisotropic, optical, and thermal properties, using Density Functional Theory (DFT) with the Cambridge Serial Total Energy Package (CASTEP) code. The elastic constants satisfied Born's criteria, confirming the thermodynamic and mechanical stability of the ANiSn compounds. Mechanical stability was further assessed through bulk modulus, shear modulus, and Poisson's ratio. Our analysis revealed that TiNiSn and ThNiSn exhibit ductile behaviour, whereas UNiSn is brittle. The calculated elastic modulus indicated that the compounds we studied are elastically anisotropic. The electronic and optical properties confirmed the semiconducting nature of these materials, with significant absorption and conductivity observed in the ultraviolet region. ANiSn is suitable for manufacturing various optoelectronic devices, such as laser diodes (LDs), photodetectors, LEDs, and UV sensors, due to its high absorption coefficient in the IR to UV regions. Additionally, measured Debye and melting temperatures confirmed that TiNiSn is more thermally conductive and can be used in high-temperature structural substances. The low minimum thermal conductivity suggests that UNiSn may be a more efficient material for thermal barrier coatings (TBC) compared to TiNiSn and ThNiSn.</div></div>","PeriodicalId":20116,"journal":{"name":"Physica B-condensed Matter","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419208","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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