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In helimagnetic metals, ac current-driven spin motions can generate emergent electric fields acting on conduction electrons, leading to emergent electromagnetic induction (EEMI). Recent experiments reveal the EEMI signal generally shows a strongly current-nonlinear response. In this study, we investigate the EEMI of Tb5Sb3, a short-period helimagnet. Using small angle neutron scattering we show that Tb5Sb3 hosts highly disordered helimagnetism with a distribution of spin-helix periodicity. The current-nonlinear dynamics of the disordered spin helix in Tb5Sb3 indeed shows up as the nonlinear electrical resistivity (real part of ac resistivity), and even more clearly as a nonlinear and huge EEMI (imaginary part of ac resistivity) response. The magnitude of the EEMI reaches as large as several tens of μH for Tb5Sb3 devices on the scale of several tens of μm, originating to noncollinear spin textures possibly even without long-range helimagnetic order. Ac current-driven spin motions in helimagnetic metals can generate emergent electric fields acting on conduction electrons, leading to emergent electromagnetic induction (EEMI). In this study, we revealed that a short-period helimagnet Tb5Sb3 may have disordered spin helix structure and provides large EEMI. [ABSTRACT FROM AUTHOR]

Magnetic skyrmions, topological vortex-like spin textures, garner significant interest due to their unique properties and potential applications in nanotechnology. While they typically form a hexagonal crystal with distinct internal magnetisation textures known as Bloch- or Néel-type, recent theories suggest the possibility for direct transitions between skyrmion crystals of different lattice structures and internal textures. To date however, experimental evidence for these potentially useful phenomena have remained scarce. Here, we discover the polar tetragonal magnet EuNiGe3 to host two hybrid skyrmion phases, each with distinct internal textures characterised by anisotropic combinations of Bloch- and Néel-type windings. Variation of the magnetic field drives a direct transition between the two phases, with the modification of the hybrid texture concomitant with a hexagonal-to-square skyrmion crystal transformation. We explain these observations with a theory that includes the key ingredients of momentum-resolved Ruderman–Kittel–Kasuya–Yosida and Dzyaloshinskii-Moriya interactions that compete at the observed low symmetry magnetic skyrmion crystal wavevectors. Our findings underscore the potential of polar magnets with rich interaction schemes as promising for discovering new topological magnetic phases.Magnetic skyrmions typically form hexagonal crystals with either uniquely Bloch or Néel-type textures. Here, a polar magnet EuNiGe3 is shown to host two skyrmion crystal phases with hexagonal and square structures, and hybrid Bloch-Néel textures. [ABSTRACT FROM AUTHOR]

Magnetic skyrmions are topologically stable swirling spin textures with particle-like character, and have been intensively studied as a candidate of high-density information bit. While magnetic skyrmions were originally discovered in noncentrosymmetric systems with Dzyaloshinskii-Moriya interaction, recently a nanometric skyrmion lattice has also been reported for centrosymmetric rare-earth compounds, such as Gd2PdSi3 and GdRu2Si2. For the latter systems, a distinct skyrmion formation mechanism mediated by itinerant electrons has been proposed, and the search of a simpler model system allowing for a better understanding of their intricate magnetic phase diagram is highly demanded. Here, we report the discovery of square and rhombic lattices of nanometric skyrmions in a centrosymmetric binary compound EuAl4, by performing small-angle neutron and resonant elastic X-ray scattering experiments. Unlike previously reported centrosymmetric skyrmion-hosting materials, EuAl4 shows multiple-step reorientation of the fundamental magnetic modulation vector as a function of magnetic field, probably reflecting a delicate balance of associated itinerant-electron-mediated interactions. The present results demonstrate that a variety of distinctive skyrmion orders can be derived even in a simple centrosymmetric binary compound, which highlights rare-earth intermetallic systems as a promising platform to realize/control the competition of multiple topological magnetic phases in a single material. Typically, skyrmions appear in magnet systems which are non-centrosymmetric. Here, using neutron and X-ray scattering, Takagi et al show the emergence of a skyrmion phase in the centrosymmetric material EuAl4. This expands the range of materials potential hosting skyrmions. [ABSTRACT FROM AUTHOR]

We succeeded in growing single crystals of $$\hbox {Yb}_{4}\hbox {Sb}_{3}$$ , Ullmannite(NiSbS)-type compounds, $$\hbox {Pd}_{3}\hbox {Bi}_{2}\hbox {Si}_{2}$$ , EuPtSi, and EuPtGe with the non-centrosymmetric cubic structures by the Bridgman method. Split Fermi surface properties are clarified for $$\hbox {Yb}_{4}\hbox {Sb}_{3}$$ and $$\hbox {Pd}_{3}\hbox {Bi}_{2}\hbox {Si}_{2}$$ . As for EuPtSi and EuPtGe with the cubic chiral structure, we observed the first-order like antiferromagnetic ordering at the Néel temperatures $$T_N=4.0\,{\rm K}$$ and 3.4 K, respectively, which are small in magnitude compared with ordering temperatures of 10-100 K in the usual divalent Eu compounds, reflecting the frustration of spins in the chiral structure. [ABSTRACT FROM AUTHOR]

In heavy-fermion compounds, f electrons show both itinerant and localized behaviour depending on the temperature. Above a characteristic temperature, T*, their magnetic properties can be described by completely ‘localized’ f-electron models. On the other hand, well below T*, their Fermi surfaces can be explained by the ‘itinerant’ f-electron model. These two models assume totally different natures of the f electrons, and how they transform between these states as a function of temperature has never been understood at the level of their electronic structures. Here, we use angle-resolved photoelectron spectroscopy to study the band structure of the heavy-fermion antiferromagnetic superconductor UPd2Al3 below and above T*, and find that the f bands, which form the Fermi surfaces at low temperatures, are excluded from the Fermi surfaces at high temperatures. This result demonstrates how the same f electrons can be both itinerant and localized. [ABSTRACT FROM AUTHOR]

We have performed 238U Mössbauer spectroscopy of uranium-based heavy fermion superconductors, UPd2Al3 and URu2Si2, in order to investigate their physical properties, mainly their magnetic properties. The slow relaxation of magnetic hyperfine interaction in a paramagnetic state and the static hyperfine field has been observed in an antiferromagnetic ordered state for each compound. The line-widths have maximum at their characteristic temperatures where their magnetic susceptibilities have maximum values. [ABSTRACT FROM AUTHOR]

In heavy-fermion compounds, f electrons show both itinerant and localized behaviour depending on the temperature. Above a characteristic temperature, T*, their magnetic properties can be described by completely ‘localized’ f-electron models. On the other hand, well below T*, their Fermi surfaces can be explained by the ‘itinerant’ f-electron model. These two models assume totally different natures of the f electrons, and how they transform between these states as a function of temperature has never been understood at the level of their electronic structures. Here, we use angle-resolved photoelectron spectroscopy to study the band structure of the heavy-fermion antiferromagnetic superconductor UPd2Al3 below and above T*, and find that the f bands, which form the Fermi surfaces at low temperatures, are excluded from the Fermi surfaces at high temperatures. This result demonstrates how the same f electrons can be both itinerant and localized. [ABSTRACT FROM AUTHOR]

In helimagnetic metals, ac current-driven spin motions can generate emergent electric fields acting on conduction electrons, leading to emergent electromagnetic induction (EEMI). Recent experiments reveal the EEMI signal generally shows a strongly current-nonlinear response. In this study, we investigate the EEMI of Tb 5 Sb 3 , a short-period helimagnet. Using small angle neutron scattering we show that Tb 5 Sb 3 hosts highly disordered helimagnetism with a distribution of spin-helix periodicity. The current-nonlinear dynamics of the disordered spin helix in Tb 5 Sb 3 indeed shows up as the nonlinear electrical resistivity (real part of ac resistivity), and even more clearly as a nonlinear and huge EEMI (imaginary part of ac resistivity) response. The magnitude of the EEMI reaches as large as several tens of μH for Tb5Sb3 devices on the scale of several tens of μm, originating to noncollinear spin textures possibly even without long-range helimagnetic order., Competing Interests: Competing interestsThe authors declare no competing interests., (© The Author(s) 2024.)