All van der Waals Fe 3 GeTe 2 /Cr 2 Ge 2 Te 6 /graphite magnetic heterojunctions have been fabricated via mechanical exfoliation and stacking, and their magnetotransport properties are studied in detail. At low bias voltages, large negative junction magnetoresistances have been observed and are attributed to spin-conserving tunneling transport across an insulating Cr 2 Ge 2 Te 6 layer. With increasing bias, a crossover to Fowler–Nordheim tunneling takes place. The negative sign of the tunneling magnetoresistance suggests that the bottom of a conduction band in Cr 2 Ge 2 Te 6 belongs to minority spins, opposite to the findings of some first-principles calculations. This work shows that the vdW heterostructures based on 2D magnetic insulators are a valuable platform to gain further insight into spin polarized tunneling transport, which is the basis for pursuing high performance spintronic devices and a large variety of quantum phenomena.
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Electronic structure and magnetic exchange interactions of Cr-based van der Waals ferromagnets. A comparative study between CrBr 3 and Cr 2 Ge 2 Te 6
Low dimensional magnetism has been powerfully boosted as a promising candidate for numerous applications. The stability of the long-range magnetic order is directly dependent on the electronic structure and the relative strength of the competing magnetic exchange constants. Here, we report a comparative pressure-dependent theoretical and experimental study of the electronic structure and exchange interactions of two-dimensional ferromagnets CrBr 3 and Cr 2 Ge 2 Te 6 . While CrBr 3 is found to be a Mott–Hubbard-like insulator, Cr 2 Ge 2 Te 6 shows a charge-transfer character due to the broader character of the Te 5p bands at the Fermi level. This different electronic behaviour is responsible for the robust insulating state of CrBr 3 , in which the magnetic exchange constants evolve monotonically with pressure, and the proximity to a metal–insulator transition predicted for Cr 2 Ge 2 Te 6 , which causes a non-monotonic evolution of its magnetic ordering temperature. We provide a microscopic understanding for the pressure evolution of the magnetic properties of the two systems.
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- NSF-PAR ID:
- 10284580
- Date Published:
- Journal Name:
- Journal of Materials Chemistry C
- Volume:
- 8
- Issue:
- 39
- ISSN:
- 2050-7526
- Page Range / eLocation ID:
- 13582 to 13589
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D0TC02003F
