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Permanent magnets are applied in many large-scale and emerging applications and are crucial components in numerous established and newly evolving technologies. Rare-earth magnets exhibit excellent hard magnetic properties; however, their applications are limited by the price and supply risk of the strategic rare-earth elements. Therefore, there is an increasing demand for inexpensive magnets without strategic elements. Here, the authors report the intrinsic highly-anisotropic magnetic properties of Co and Si co-doped single crystals (Fe1−yCoy)2P1−xSix (y ≈ 0.09). Co increases Curie temperature TC; Si doping decreases magnetocrystalline anisotropy K1 and also increases TC significantly because of the enhanced interlayer interaction. The maximum room temperature magnetocrystalline anisotropy K1 = 1.09 MJ m−3 is achieved for x = 0.22, with saturation magnetization µ0Ms = 0.96 T and TC = 506 K. The theoretical maximum energy product is one of the largest for any magnet without a rare earth or Pt. Besides its promising intrinsic magnetic properties and absence of any strategic elements, other advantages are phase stability at high temperatures and excellent corrosion resistance, which make this material most promising for permanent magnetic development that will have a positive influence in industry and daily life. © 2021 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH. ; This work was financially supported by the Joint Initiative for Research and Innovation within the Fraunhofer and Max Planck cooperation program, an Advanced Grant from the European Research Council (no. 742068) "TOPMAT," the European Union's Horizon 2020 research and innovation programme (no. 824123) "SKYTOP," the European Union's Horizon 2020 research and innovation programme (no. 766566) "ASPIN," the Deutsche Forschungsgemeinschaft (project ID 258499086) "SFB 1143," the Deutsche Forschungsgemeinschaft (project IDs FE 633/30‐1, RE 1164/6‐1, and LU 2261/2‐1) "SPP Skyrmionics", and the DFG through the Würzburg‐Dresden Cluster ...

The topological Hall effect (THE), induced by the Berry curvature that originates from non-zero scalar spin chirality, is an important feature for mesoscopic topological structures, such as skyrmions. However, the THE might also arise from other microscopic non-coplanar spin structures in the lattice. Thus, the origin of the THE inevitably needs to be determined to fully understand skyrmions and find new host materials. Here, we examine the Hall effect in both, bulk- and micron-sized lamellar samples of MnBi. The sample size affects the temperature and field range in which the THE is detectable. Although a bulk sample exhibits the THE only upon exposure to weak fields in the easy-cone state, in micron-sized lamella the THE exists across a wide temperature range and occurs at fields near saturation. Our results show that both the non-coplanar spin structure in the lattice and topologically non-trivial skyrmion bubbles are responsible for the THE, and that the dominant mechanism depends on the sample size. Hence, the magnetic phase diagram for MnBi is size-dependent. Our study provides an example in which the THE is simultaneously induced by two mechanisms, and builds a bridge between mesoscopic and microscopic magnetic structures. © 2022. ; This work was financially supported by an Advanced Grant from the European Research Council (No. 742068 ) "TOPMAT," the European Union's Horizon 2020 research and innovation programme (No. 824123 ) "SKYTOP," the European Union's Horizon 2020 research and innovation programme (No. 766566 ) "ASPIN," the Deutsche Forschungsgemeinschaft (Project-ID 258499086) "SFB 1143," the Deutsche Forschungsgemeinschaft (Project-IDs FE 633/30-1, RE 1164/6-1 and LU 2261/2-1) "SPP Skyrmionics," the DFG through the Würzburg-Dresden Cluster of Excellence on Complexity and Topology in Quantum Matter ct.qmat (EXC 2147, Project-ID 39085490). I.S. is grateful to Deutsche Forschungsgemeinschaft for supporting this work through project SO 1623/2-1. D.W. has received funding from the European Research ...

Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC). Weyl semimetals are crystals in which electron bands cross at isolated points in momentum space. Associated with each crossing point (or Weyl node) is a topological invariant known as the Berry monopole charge. The circular photogalvanic effect (CPGE), whereby circular polarized light generates a helicity-dependent photocurrent, is a notable example of a macroscopic property that emerges directly from the topology of the Weyl semimetal band structure. Recently, it was predicted that the amplitude of the CPGE associated with optical transitions near a Weyl node is proportional to its monopole charge. In chiral Weyl systems, nodes of opposite charge are nondegenerate, opening a window of wavelengths where the CPGE resulting from uncompensated Berry charge can emerge. Here, we report measurements of CPGE in the chiral Weyl semimetal RhSi, revealing a CPGE response in an energy window that closes at 0.65 eV, in agreement with the predictions of density functional theory.

The increasing demand for computer data storage with a higher recording density can be addressed by using smaller magnetic objects, such as bubble domains. Small bubbles predominantly require a strong saturation magnetization combined with a large magnetocrystalline anisotropy to resist self-demagnetization. These conditions are well satisfied for highly anisotropic materials. Here, we study the domain structure of thin Nd2Fe14B lamellae. Magnetic bubbles with a minimum diameter of 74 nm were observed at room temperature, approaching even the range of magnetic skyrmions. The stripe domain width and the bubble size are both thickness dependent. Furthermore, a kind of bubble was observed below the spin-reorientation transition temperature that combine bubbles with opposite helicity. In this paper, we reveal Nd2Fe14B to be a good candidate for a high-density magnetic bubble-based memory. © 2022 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Open access publication funded by the Max Planck Society. ; This paper was financially supported by an Advanced Grant from the European Research Council (No. 742068) "TOPMAT," the European Union's Horizon 2020 research and innovation program (No. 824123) "SKYTOP," the European Union's Horizon 2020 research and innovation program (No. 766566) "ASPIN," the Deutsche Forschungsgemeinschaft (Project-ID 258499086) "SFB 1143," the Deutsche Forschungsgemeinschaft (DFG; Project-IDs FE 633/30-1, RE 1164/6-1, and LU 2261/2-1) "SPP Skyrmionics," the DFG through the Würzburg-Dresden Cluster of Excellence on Complexity and Topology in Quantum Matter ct.qmat (EXC 2147, Project-ID 39085490). I.S. would like to express his gratitude to the DFG for supporting this paper through Project SO ...