Julian Klein1,Thang Pham1,Myung-Geun Han2,Joachim Thomsen1,3,Michael Ziebel4,Jonathan Curtis3,Michael Lorke5,Matthias Florian5,Alexander Steinhoff5,Kate Reidy1,Kierstin Torres1,Ren Wiscons4,Xavier Roy4,Jan Luxa6,Zdeněk Sofer6,Frank Jahnke5,Yimei Zhu2,Prineha Narang3,Frances Ross1
Massachusetts Institute of Technology1,Brookhaven National Laboratory2,John A. Paulson School of Engineering and Applied Sciences3,Department of Chemistry, Columbia University4,Institut für Theoretische Physik, Universität Bremen5,Department of Inorganic Chemistry, University of Chemistry and Technology Prague6
Julian Klein1,Thang Pham1,Myung-Geun Han2,Joachim Thomsen1,3,Michael Ziebel4,Jonathan Curtis3,Michael Lorke5,Matthias Florian5,Alexander Steinhoff5,Kate Reidy1,Kierstin Torres1,Ren Wiscons4,Xavier Roy4,Jan Luxa6,Zdeněk Sofer6,Frank Jahnke5,Yimei Zhu2,Prineha Narang3,Frances Ross1
Massachusetts Institute of Technology1,Brookhaven National Laboratory2,John A. Paulson School of Engineering and Applied Sciences3,Department of Chemistry, Columbia University4,Institut für Theoretische Physik, Universität Bremen5,Department of Inorganic Chemistry, University of Chemistry and Technology Prague6
The experimental observation of long-range magnetic order in 2D van der Waals (vdW) layered materials has triggered great interest for the study of low-dimensional magnetism. [1] Recently, the layered magnetic semiconductor CrSBr [2] has been rediscovered, a material where vibrational, optical and electronic properties are strongly correlated with its magnetic order. The air stability, energy band gap of approximately 1.6eV and high Néel temperature (132 K) offer many exciting avenues for scientific exploration. [3, 4] Moreover, CrSBr exhibits an intriguing and mostly unexplored magnetic phase diagram with an intermediate ferromagnetic transition at ~132-150 K. [3] The unique properties of CrSBr motivate detailed studies with the goal to establish a new platform for the exploration and controlled design of low-dimensional magnetic excitations.<br/>Here, we explore the structural and magnetic properties of CrSBr using electron microscopy. In high-resolution scanning transmission electron microscopy, we observe that controlled dosing with electrons creates a local phase transformation. Strikingly, the new phase is also a 2D layered structure, but its layers are perpendicular to those in the original material. [5] Ab-initio and spin-wave theory suggest that the individual layers in the new phase are magnetic, and the material has an energy gap and a fully spin-polarized band structure. Moreover, we explore the magnetic structure of CrSBr using cryogenic Lorentz transmission electron microscopy. Throughout the temperature range associated with the antiferromagnetic to paramagnetic phase transition we observe the formation of magnetic textures. Most strikingly, the magnetic textures persist down to the monolayer limit, clearly reflecting the 2D character of the magnetic structure in CrSBr that persists throughout this magnetic phase transition. The observation suggests the emergence of skyrmion-like magnetic features and an exotic higher order phase transition.<br/>To conclude, we provide a broad electron microscopic study of the emergent 2D magnet CrSBr to reveal the intricate magnetic structure in the intermediate phase transition and explore new avenues to create magnetic textures on the nano scale. We suggest that CrSBr and other air-stable magnets that can show similar engineerability of their crystal structures have the potential to become versatile platforms for the design, measurement, and application of nanoscale magnetic textures for use in quantum and memory technologies.<br/>[1] Huang, B. et al. <i>Nature</i> <b>546</b>, 270–273 (2017)<br/>[2] Göser, O. et al. <i>J. Magn. Magn. Mater.</i> <b>92</b>, 129 (1990)<br/>[3] Telford, E. J. et al. <i>Adv. Mater.</i> <b>32</b>, 1 (2020)<br/>[4] Wilson, N. et al. <i>Nature Mater.</i> (2021)<br/>[5] Klein, J. et al. <i>arXiv:2107.00037</i> (2021)