The synthesis of two-dimensional van der Waals magnets has paved the way for both technological applications and fundamental research on magnetism confined to ultra-small length scales. Edge magnetic moments in ferromagnets are expected to be less magnetized than in the sample interior because of the reduced amount of neighboring ferromagnetic spins at the sample edge. We recently demonstrated that CrGeTe3(CGT) flakes thinner than 10 nm are hard ferromagnets; i.e., they exhibit an open hysteresis loop. In contrast, thicker flakes exhibit zero net remnant field in the interior, with hard ferromagnetism present only at the cleaved edges. This experimental observation suggests that a nontrivial interaction exists between the sample edge and the interior. Here, we demonstrate that artificial edges fabricated by focus ion beam etching also display hard ferromagnetism. This enables us to write magnetic nanowires in CGT directly and use this method to characterize the magnetic interaction between the interior and edge. The results indicate that the interior saturation and depolarization fields depend on the lateral dimensions of the sample. Most notably, the interior region between the edges of a sample narrower than 300 nm becomes a hard ferromagnet, suggesting an enhancement of the magnetic exchange induced by the proximity of the edges. Last, we find that the CGT regions amorphized by the gallium beam are nonmagnetic, which introduces a novel method to tune the local magnetic properties of CGT films, potentially enabling integration into spintronic devices.
Bibliographical noteFunding Information:
We would like to thank A. Capua, Y. Paltiel and B. Yan for fruitful discussions. Devices for this project were fabricated at the Hebrew University center for Nanoscience. This work was supported by the European Research Council (ERC) Foundation grant No. 802952. The international collaboration on this work was fostered by the EU-COST Action CA21144. H.S. acknowledges funding provided by the DFG Priority program grant 443404566 and Israel Science Foundation (ISF) grant 861/19. O.M. is grateful for support from the Academia Sinica – Hebrew University Research Program, the ISF grant no. 576/21, and the Harry de Jur Chair in Applied Science. S.G. acknowledges support from the ISF grant No. 586/22. H.S. and E.H. acknowledge support from the Spanish State Research Agency (PID2020-114071RB-I00, CEX2018-000805-M) and the Comunidad de Madrid through the NANOMAGCOST-CM program (Program No.S2018/NMT-4321).
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- edge magnetism
- magnetic imaging
- scanning SQUID microscopy
- van der Waals ferromagnet