Influence of magnetism, strain and pressure on the band topology of EuCd2_2As2_2

Motivated by the wealth of proposals and realizations of nontrivial topological phases in EuCd$_2$As$_2$, such as a Weyl semimetallic state and the recently discussed semimetallic versus semiconductor behavior in this system, we analyze in this work the role of the delicate interplay of Eu magnetism, strain and pressure on the realization of such phases. For that we invoke a combination of a group theoretical analysis with ab initio density functional theory calculations and uncover a rich phase diagram with various non-trivial topological phases beyond a Weyl semimetallic state, such as axion and topological crystalline insulating phases, and discuss their realization

Crystal Thermal Transport in Altermagnetic RuO2

We demonstrate the emergence of a pronounced thermal transport in the recently discovered class of magnetic materials-altermagents. From symmetry arguments and first principles calculations performed for the showcase altermagnet, RuO2, we uncover that crystal Nernst and crystal thermal Hall effects in this material are very large and strongly anisotropic with respect to the Neel vector. We find the large crystal thermal transport to originate from three sources of Berry's curvature in momentum space: the pseudo-nodal surfaces, the Weyl fermions due to crossings between well-separated bands, and the spin-flip ladder transitions, defined by transitions among very weakly spin-split states of similar dispersion crossing the Fermi surface. Moreover, we reveal that the anomalous thermal and electrical transport coefficients in RuO2 are linked by an extended Wiedemann-Franz law in a temperature range much wider than expected for conventional magnets. Our results suggest that altermagnets may assume a leading role in realizing concepts in spincaloritronics not achievable with ferromagnets or antiferromagnets.Comment: 6 page

Saturation of the anomalous Hall effect at high magnetic fields in altermagnetic RuO2

Observations of the anomalous Hall effect in RuO2 and MnTe have demonstrated unconventional time-reversal symmetry breaking in the electronic structure of a recently identified new class of compensated collinear magnets, dubbed altermagnets. While in MnTe, the unconventional anomalous Hall signal accompanied by a vanishing magnetization is observable at remanence, the anomalous Hall effect in RuO2 is excluded by symmetry for the Néel vector pointing along the zero-field [001] easy-axis. Guided by a symmetry analysis and ab initio calculations, a field-induced reorientation of the Néel vector from the easy-axis toward the [110] hard-axis was used to demonstrate the anomalous Hall signal in this altermagnet. We confirm the existence of an anomalous Hall effect in our RuO2 thin-film samples, whose set of magnetic and magneto-transport characteristics is consistent with the earlier report. By performing our measurements at extreme magnetic fields up to 68 T, we reach saturation of the anomalous Hall signal at a field Hc ≃ 55 T that was inaccessible in earlier studies but is consistent with the expected Néel-vector reorientation field

Saturation of the anomalous Hall effect at high magnetic fields in altermagnetic RuO2

Observations of the anomalous Hall effect in RuO$_2$ and MnTe have demonstrated unconventional time-reversal symmetry breaking in the electronic structure of a recently identified new class of compensated collinear magnets, dubbed altermagnets. While in MnTe the unconventional anomalous Hall signal accompanied by a vanishing magnetization is observable at remanence, the anomalous Hall effect in RuO$_2$ is excluded by symmetry for the N\'eel vector pointing along the zero-field [001] easy-axis. Guided by a symmetry analysis and ab initio calculations, a field-induced reorientation of the N\'eel vector from the easy-axis towards the [110] hard-axis was used to demonstrate the anomalous Hall signal in this altermagnet. We confirm the existence of an anomalous Hall effect in our RuO$_2$ thin-film samples whose set of magnetic and magneto-transport characteristics is consistent with the earlier report. By performing our measurements at extreme magnetic fields up to 68 T, we reach saturation of the anomalous Hall signal at a field $H_{\rm c} \simeq$ 55 T that was inaccessible in earlier studies, but is consistent with the expected N\'eel-vector reorientation field.Comment: 4 figure

Direct observation of altermagnetic band splitting in CrSb thin films

Altermagnetism represents an emergent collinear magnetic phase with compensated order and an unconventional alternating even-parity wave spin order in the non-relativistic band structure. We investigate directly this unconventional band splitting near the Fermi energy through spinintegrated soft X-ray angular resolved photoemission spectroscopy. The experimentally obtained angle-dependent photoemission intensity, acquired from epitaxial thin films of the predicted altermagnet CrSb, demonstrates robust agreement with the corresponding band structure calculations. In particular, we observe the distinctive splitting of an electronic band on a low-symmetry path in the Brilliouin zone that connects two points featuring symmetry-induced degeneracy. The measured large magnitude of the spin splitting of approximately 0.6 eV and the position of the band just below the Fermi energy underscores the signifcance of altermagnets for spintronics based on robust broken time reversal symmetry responses arising from exchange energy scales, akin to ferromagnets, while remaining insensitive to external magnetic fields and possessing THz dynamics, akin to antiferromagnets.Comment: 10 pages, 7 figures (including supplementary information

Saturation of the anomalous Hall effect at high magnetic fields in altermagnetic RuO2

Observations of the anomalous Hall effect in RuO2 and MnTe have demonstrated unconventional time-reversal symmetry breaking in the electronic structure of a recently identified new class of compensated collinear magnets, dubbed altermagnets. While in MnTe, the unconventional anomalous Hall signal accompanied by a vanishing magnetization is observable at remanence, the anomalous Hall effect in RuO2 is excluded by symmetry for the Néel vector pointing along the zero-field [001] easy-axis. Guided by a symmetry analysis and ab initio calculations, a field-induced reorientation of the Néel vector from the easy-axis toward the [110] hard-axis was used to demonstrate the anomalous Hall signal in this altermagnet. We confirm the existence of an anomalous Hall effect in our RuO2 thin-film samples, whose set of magnetic and magneto-transport characteristics is consistent with the earlier report. By performing our measurements at extreme magnetic fields up to 68 T, we reach saturation of the anomalous Hall signal at a field Hc ≃ 55 T that was inaccessible in earlier studies but is consistent with the expected Néel-vector reorientation field

Commented translation of a text on science and technology

Cílem této bakalářské práce je překlad technického textu z českého jazyka do anglického a okomentovat aspekty překladu a problémy s tím spojené. Vybraný text jsou elektronická skripta, sdílená na e-learningu a používána Vysokým Učením Technickým v Brně výhradně pro výukové účely v oboru mikroelektrotechnika. Teoretická část uvádí teorii překladu, její procedury, postupy a typy. Také obsahuje popis funkčních stylů, obzvláště stylu odborného. Praktická část je reprezentována překladem prvních dvou kapitol – Úvodem a technologií CMOS. Závěrečná – analytická část obsahuje komentáře různých problémů z odlišných lingvistických hledisek.The aim of this bachelor thesis is a translation of a technical text from Czech to the English language and comment on the aspects of the translation and its problems. The chosen text is an electronic textbook, distributed on e-learning and used by the Brno University of Technology solely for educational purposes on the microelectronics field. Theoretical part presents the translation theory, its processes, procedures and types. It also contains a description of the functional styles, especially the style of science and technology. The practical part is represented by the translation of the first two chapters - Introduction and the CMOS technology. The final – analytical part contains the commentary on various issues from different linguistic perspectives.

Inverse Faraday Effect in altermagnets from first-principles

While the understanding of altermagnetism is still in a very early stage,it is expected to play a role in various fields of condensed matterresearch, for example spintronics, caloritronics and superconductivity[1]. Concerning the field of optical magnetism, it is intriguing to studywhether altermagnets can host magnetization dynamic effects withdifferent properties from ferromagnets and antiferromagnets. Here wechoose RuO2, a prototype metallic altermagnet with a giant spinsplitting, and CoF2, an experimentally well studied insulatingaltermagnet, and calculate the inverse Faraday effect (IFE), i.e., laserinducedspin and orbital magnetizations, from first-principles

Competitive actions of MnSi in the epitaxial growth of Mn5Si3 thin films on Si(111)

International audienceSome magnetically ordered phases of the Mn5Si3 crystal are proving to be prototypes for the study of thenew fundamental spin physics related to the spontaneous breaking of the time-reversal symmetry despite a zeronet magnetization. Here, we report on a route to grow epitaxial Mn5Si3 thin films on Si(111). To this end, weuse Mn and Si codeposition in a molecular beam epitaxy system and carefully tune the deposition rates, thegrowth temperature, and the annealing temperature. We assessed the silicide phase-formation and morphologyusing reflection high-energy electron diffraction, x-ray diffraction, high-resolution transmission electron mi-croscopy (HRTEM) and atomic force microscopy. Layers containing only Mn5Si3 could be stabilized undervery restrictive conditions, by tuning the Mn/Si flux ratio to match the compound stoichiometry and adjustingthe substrate temperature during growth to 443 K. HRTEM imaging revealed the existence of an interfacialamorphous layer of few nanometers thickness. Annealing the heterostructure up to 573 K led to the formationof MnSi at the vicinity of the Mn5Si3/Si(111) interface, which significantly reduced the nucleation barrier ofMn5Si3. High-quality crystalline Mn5Si3 thin films were then formed with the following epitaxial relationships:Mn5Si3 (0001)[011̄0]//MnSi(111)[2̄11]//Si(111)[11̄0]. Our experiments showed that the formation of MnSi isenhanced at a growth temperature above 473 K or for a longer annealing step, while the crystalline quality of theMn5Si3 overlayer is correspondingly degraded leading to textured thin films. The growth pathways and structuralproperties of the manganese silicides can be rationalized in terms of reactions maximizing the free-energylowering rate. Moreover, we found that the magnetic and the magnetotransport properties can be used as anefficient tool to track both Mn5Si3 crystallinity and proportion in the deposited layers