Journal of Physics: Condensed Matter最新文献_第6页

Magnetic irreversibility and magnetization processes in Ni₅Al₃/NiO core/shell nanoparticle system. Ni5Al3/NiO 核/壳纳米粒子系统中的磁不可逆性和磁化过程。

IF 2.3 4区物理与天体物理

Journal of Physics: Condensed Matter Pub Date : 2024-08-14 DOI: 10.1088/1361-648X/ad69ee

P V Prakash Madduri, S N Kaul

{"title":"Magnetic irreversibility and magnetization processes in Ni5Al3/NiO core/shell nanoparticle system.","authors":"P V Prakash Madduri, S N Kaul","doi":"10.1088/1361-648X/ad69ee","DOIUrl":"10.1088/1361-648X/ad69ee","url":null,"abstract":"This work brings out many interesting facets of magnetism in the Ni5Al3/NiO core/shell nanoparticle system. Theweakandstrongmagnetic irreversibility lines (TWI(H)andTSI(H)) reproduce the previously reportedH - Tphase diagram at fieldsH⩽30 Oe, but strong departures occur forH > 30 Oe. Comparison with the theoretically predictedH - Tphase diagram allows us to identifyTWIwithTCG+SG, where the paramagnetic (PM)-chiral glass (CG) and PM-spin glass (SG) phase transitions occursimultaneously, andTSIwithTSG, the temperature at which transition to the replica symmetry breakingSGstate takes place. TheTSI(H)transition line abruptly ends at the point (H≃30 Oe,T≃90K). AsHexceeds 30 Oe, a new transition appears which gets completely suppressed at fieldsH>1 kOewhere the magnetic irreversibility ceases to exist. Nointrinsiclong-range ferromagnetic ordering exists but fields as low as 3 kOe suffice to induce long-range ferromagnetic order. At fixed temperatures, the magnetocrystalline anisotropy fluctuations essentially govern the 'approach-to-saturation' in magnetization for fields in the range 3 - 70 kOe. The present nanocrystalline system behaves as an isotropic system with random easy axis in which the magnetization reversal occurs through the coherent rotation of the magnetizations of weakly-interacting single-domain Ni5Al3particles. Saturation magnetization, likeM(T) atH⩾2 kOe, exhibits an anomalous upturn at temperatures below ≈ 30 K. This upturn is associated with the anomalous softening of spin-wave modes which results in the thermal excitation of a large number of non-equilibrium (finite lifetime) magnons. At sub-Kelvin temperatures, these magnons undergo Bose-Einstein condensation.","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141860130","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}

引用次数: 0

Magnetization dynamics in single and trilayer nanowires. 单层和三层纳米线的磁化动力学。

IF 2.3 4区物理与天体物理

Journal of Physics: Condensed Matter Pub Date : 2024-08-14 DOI: 10.1088/1361-648X/ad6c9a

Mahathi Kuchibhotla, Arabinda Haldar, Adekunle Olusola Adeyeye

{"title":"Magnetization dynamics in single and trilayer nanowires.","authors":"Mahathi Kuchibhotla, Arabinda Haldar, Adekunle Olusola Adeyeye","doi":"10.1088/1361-648X/ad6c9a","DOIUrl":"10.1088/1361-648X/ad6c9a","url":null,"abstract":"We have studied the magnetization dynamics of single Py(t) (t= 20 nm, 50 nm) and trilayer [Py(50)/Pd(tPd)/Py(20)] nanowire arrays fabricated over large areas using deep ultraviolet lithography technique. The dynamic properties are sensitive to the field orientation and magnetic film thicknesses. A single resonant mode corresponding to the excitations at the bulk part of the wire is detected in all the single-layer nanowire arrays. Furthermore, the spacer layer thickness influenced the dynamic properties in trilayer samples due to the different coupling mechanisms. A single resonant mode is observed intPd= 2 nm trilayer nanowires with a sharp frequency jump from 13 GHz to 15 GHz across the reversal regime. This indicates the exchange coupling and the coherence in magnetization precession in the ferromagnetic layers. On the other hand, wires with 10 nm-spacer display two well-resolved modes separated by ∼3 GHz with a gradual change in frequency across the reversal regime from-26mT to-46mT, indicating the presence of long-range dipolar interactions instead of exchange coupling. The spacer layer of the proposed spin-valve-type structure can be tailored for desired microwave splitters or combiners.","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141902033","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}

引用次数: 0

The spin-SHeisenberg antiferromagnet on the orthogonal-dimer lattice. 正交二聚体晶格上的自旋-海森堡反铁磁体

IF 2.3 4区物理与天体物理

Journal of Physics: Condensed Matter Pub Date : 2024-08-13 DOI: 10.1088/1361-648X/ad6522

Hiroki Nakano, Toru Sakai

引用次数: 0

Triplon analysis of magnetic disorder and order in maple-leaf Heisenberg magnet. 枫叶海森堡磁体中磁性无序和有序的 Triplon 分析。

IF 2.3 4区物理与天体物理

Journal of Physics: Condensed Matter Pub Date : 2024-08-13 DOI: 10.1088/1361-648X/ad69f4

Pratyay Ghosh

引用次数: 0

A thorough investigation of the antiferromagnetic resonance. 对反铁磁共振的深入研究

IF 2.3 4区物理与天体物理

Journal of Physics: Condensed Matter Pub Date : 2024-08-13 DOI: 10.1088/1361-648X/ad69f0

A R Moura

引用次数: 0

A complex magnetic study: evidence of spin-glass transition below long-range magnetic ordering and its correlation with renormalization of phonon modes. 复杂磁性研究：长程磁有序化以下自旋玻璃转变的证据及其与声子模式重正化的相关性。

IF 2.3 4区物理与天体物理

Journal of Physics: Condensed Matter Pub Date : 2024-08-12 DOI: 10.1088/1361-648X/ad69f2

Sipun Mohanty, Samrat Mukherjee

{"title":"A complex magnetic study: evidence of spin-glass transition below long-range magnetic ordering and its correlation with renormalization of phonon modes.","authors":"Sipun Mohanty, Samrat Mukherjee","doi":"10.1088/1361-648X/ad69f2","DOIUrl":"10.1088/1361-648X/ad69f2","url":null,"abstract":"In this paper, we report a complex magnetic behavior arising due to the interplay of three active magnetic cations (Nd/Sm, Co and Ir), forming 3d-5d-4f magnetic sublattices. The B-site ordered double perovskites Nd2CoIrO6and Sm2CoIrO6were successfully prepared by conventional solid-state method. Detailed structural analysis revealed that both samples crystallized in monoclinic structure with P21/n (No.-14) space group. X-ray photoelectron spectroscopy analysis confirms the presence of multiple oxidation states of Ir (i.e. Ir4+and Ir5+). Both samples show a paramagnetic-ferrimagnetic (TFiM) transition around 100 K, additionally, a low temperature transition is observed at around 10 K in the SCIO sample. This FM-like behavior of the samples is attributed to the antiparallel alignment of the Co2+and Ir4+spins, resulting in FiM ordering. The ac susceptibility analysis confirms a spin glass type transition just below the long-range ordering temperature in NCIO sample, The obtained characteristic flipping time of a single spin from both the law (Power law and Vogel-Fulcher law) and nonzero Vogel-Fulcher temperature (T0≃ 89.1 K) further verified the existence of cluster spin-glass behavior below the ordering temperature. The temperature evolution of phonon modes (up to 4 K) suggests that the phonon mode above the magnetic ordering temperature is mainly governed by the lattice degrees of freedom; notable renormalization of the mode frequency below the ordering temperature is due to the coupling of lattice with the underlying magnetic degrees of freedom.","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2024-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141860084","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}

引用次数: 0

Topological tight binding models on some non-trivial lattices: union of geometry, flat bands and topology. 一些非三维网格上的拓扑紧密结合模型：几何、平带和拓扑的结合。

IF 2.3 4区物理与天体物理

Journal of Physics: Condensed Matter Pub Date : 2024-08-12 DOI: 10.1088/1361-648X/ad5c32

Bharathiganesh Devanarayanan

{"title":"Topological tight binding models on some non-trivial lattices: union of geometry, flat bands and topology.","authors":"Bharathiganesh Devanarayanan","doi":"10.1088/1361-648X/ad5c32","DOIUrl":"10.1088/1361-648X/ad5c32","url":null,"abstract":"We introduce a topological tight binding model based on certain rules that we have formulated to study systems with certain non-trivial bulks. These rules allow us to study bulks that have twists and branching. We discuss certain cases in the SAB model with different number of bands, exhibiting several interesting physical properties. For every bulk there can be two sets of configurations: the orientable and the non-orientable configuration. The later exhibits several non-trivial physical properties like exact flat bands (exactly at particle hole symmetry level), zero energy states localised in the bulk, topological edge states etc. We then discuss a three band non-orientable SAB model which is easy to visualise. We also investigate the effects of disorder (both chiral symmetry preserving and breaking) in the non-orientable configurations hosting flat bands. We find for chiral symmetry preserving disorders, some of them (non-degenerate flat band) are robust to large disorders while others (degenerate flat band) exhibit an insulator to metal transition beyond certain critical disorder strength due to band gap closing as a result of the broadening of the zero energy states. For chiral symmetry breaking disorders, in both the cases the zero energy bulk states broaden and close the gap beyond certain critical disorder strength.","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2024-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141457606","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}

引用次数: 0

The Casimir-like effect induced by active nematics. 主动线粒体诱发的卡西米尔效应

IF 2.3 4区物理与天体物理

Journal of Physics: Condensed Matter Pub Date : 2024-08-12 DOI: 10.1088/1361-648X/ad69f1

Fahimeh Karimi Pour Haddadan

{"title":"The Casimir-like effect induced by active nematics.","authors":"Fahimeh Karimi Pour Haddadan","doi":"10.1088/1361-648X/ad69f1","DOIUrl":"https://doi.org/10.1088/1361-648X/ad69f1","url":null,"abstract":"We consider an active nematic phase and use hydrodynamical equations of it to model the activity as an internal field. The interaction of this field with the nematic director in a confined geometry is included in the Hamiltonian of the system. Based on this model Hamiltonian and the standard field theoretical approach, the Casimir-like force induced between the boundaries of such a confined film is discussed. The force depends on the geometrical shape and the dynamical character of the constituents of our active phase, as well as the anchoring conditions. For homeotropically aligned rod-like particles which in principle tend to align along a planar flow field, extensile activity enhances the attraction present in a thin nematic film. As the film thickness increases the force reduces. Beyond a critical thickness, a planar flow field instantaneous to a bend distortion sets in. Near but below the threshold of this activity-induced instability, the force crosses zero and repulsively diverges right at the critical threshold of this so-called flow instability. For contractile rods, in the same geometry as above, the structure is stable and the Casimir-like force diminishes by an exponential factor as a function of the film thickness. On the other side for a planar director alignment, rod-like contractile particles can induce opposite shear flows at the boundaries creating a splay distortion for the director between the plates. In this configuration, we obtain the same universal pretransitional behavior for the force as above. Vice versa, for extensile rod-like particles in this geometry, the director fluctuations become massive and the Casimir-like force diminishes again by an exponential factor as the film thickness increases. The effect of the active field on thermal fluctuations of the director and the fluctuation-induced Casimir force per area is derived through a \"semi\"-dynamical approach as well. However, the results of the calculation due to a mathematical sum over the fluctuating modes do not lead to an approved closed form.","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2024-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141916932","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}

引用次数: 0

Phase shift of coherent magnetization dynamics after ultrafast demagnetization in strongly quenched nickel thin films. 强淬火镍薄膜超快退磁后相干磁化动力学的相移。

IF 2.3 4区物理与天体物理

Journal of Physics: Condensed Matter Pub Date : 2024-08-12 DOI: 10.1088/1361-648X/ad68b2

Akira Lentfert, Anulekha De, Laura Scheuer, Benjamin Stadtmüller, Georg von Freymann, Martin Aeschlimann, Philipp Pirro

{"title":"Phase shift of coherent magnetization dynamics after ultrafast demagnetization in strongly quenched nickel thin films.","authors":"Akira Lentfert, Anulekha De, Laura Scheuer, Benjamin Stadtmüller, Georg von Freymann, Martin Aeschlimann, Philipp Pirro","doi":"10.1088/1361-648X/ad68b2","DOIUrl":"10.1088/1361-648X/ad68b2","url":null,"abstract":"The remagnetization process after ultrafast demagnetization can be described by relaxation mechanisms between the spin, electron, and lattice reservoirs. Thereby, collective spin excitations in form of spin waves and their angular momentum transfer play an important role on the longer timescales. In this work, we address the question whether the magnitude of demagnetization-the so-called quenching-affects the coherency and the phase of the excited spin waves. We present a study of coherent magnetization dynamics in thin nickel films after ultrafast demagnetization using the all-optical, time-resolved magneto-optical Kerr-effect technique. The largest coherent precession amplitude was observed for strongly quenched systems, indicating a well-defined precession phase for all pump pulses at a demagnetization of up to 90% in this system. Moreover, the phase of the excited spin-waves in Ni increases with the pump fluence, indicating a delayed start of the precession during the remagnetization. We compare these findings to recent studies in Ni80Fe20(permalloy), to evaluate the influence of the magneto-elastic coupling and non-linear spin-wave dynamics on the magnetization dynamics.","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2024-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141792749","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}

引用次数: 0

Iso-structural phase transition in pyrochlore iridates (Sm _{1-x}$Bi_x)₂Ir₂O₇(x= 0, 0.02, and 0.10): high-pressure Raman and x-ray diffraction studies. 热绿石铱酸盐 (Sm1-xBix)2Ir2O7 (x = 0、0.02 和 0.10) 中的等结构相变：高压拉曼和 X 射线衍射研究。

IF 2.3 4区物理与天体物理

Journal of Physics: Condensed Matter Pub Date : 2024-08-09 DOI: 10.1088/1361-648X/ad69ed

M Rosalin, K A Irshad, Boby Joseph, Prachi Telang, Surjeet Singh, D V S Muthu, A K Sood

{"title":"Iso-structural phase transition in pyrochlore iridates (Sm _{1-x}$Bix)2Ir2O7(x= 0, 0.02, and 0.10): high-pressure Raman and x-ray diffraction studies.","authors":"M Rosalin, K A Irshad, Boby Joseph, Prachi Telang, Surjeet Singh, D V S Muthu, A K Sood","doi":"10.1088/1361-648X/ad69ed","DOIUrl":"10.1088/1361-648X/ad69ed","url":null,"abstract":"The pyrochlore iridates,A2Ir2O7, show a wide variety of structural, electronic, and magnetic properties controlled by the interplay of different exchange interactions, which can be tuned by external pressure. In this work, we report pressure-induced iso-structural phase transitions at ambient temperature using synchrotron-based x-ray diffraction (up to ∼20 GPa) and Raman-scattering measurements (up to ∼25 GPa) of the pyrochlore series (Sm_{1-x}Bix)2Ir2O7(x= 0, 0.02, and 0.10). Our Raman and x-ray data suggest an iso-structural transition in Sm2Ir2O7atPc∼ 11.2 GPa, associated with the rearrangement of IrO6octahedra in the pyrochlore lattice. The transition pressure decreases to ∼10.2 and 9 GPa forx= 0.02 and 0.10, respectively. For all the samples, the linewidth of three phonons associated with Ir-O-Ir (A1gandEg) and Ir-O (T2g4) vibrations show anomalous decrease up toPc, due to decrease in electron-phonon interaction.","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141860129","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}

引用次数: 0