Tuning the Magnetic Properties of CrI₃ Using Ni Thin Film Deposition for Applications in Spintronic Devices

Journal Article · Thu Jan 30 00:00:00 EST 2025 · ACS Applied Nano Materials

DOI:https://doi.org/10.1021/acsanm.4c06641· OSTI ID:2574561

Nnokwe, Cynthia ^[1]; Cunningham, Connor J. ^[2]; Liu, Wenhao ^[3]; Ye, Gaihua ^[1]; Nguyen, Tri ^[1]; Wu, Kai ^[1]; Hemesath, Colin ^[4]; Sadler, Caden ^[4]; Lukashev, Pavel ^[4]; Zhai, Zixin ^[3]; Lv, Bing ^[3]; Yan, Jia-An ^[5]; Shand, Paul M. ^[4]; Stollenwerk, Andrew James ^[4]; He, Rui ^[1]

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1. Texas Tech University, Lubbock, TX (United States)
2. Department of Physics; University of Northern Iowa
3. The University of Texas at Dallas, Richardson, TX (United States)
4. University of Northern Iowa, Cedar Falls, IA (United States)
5. Towson University, MD (United States)

Chromium triiodide (CrI₃), a van der Waals magnet, has recently been shown to host Ising ferromagnetism down to the monolayer limit. It is a potentially important material in 2D magnet-based applications, such as magnetic sensors and spintronic devices. Prior studies have revealed the coexistence of two different types of interlayer magnetic coupling, the antiferromagnetic (AFM) coupling near the surface and ferromagnetic (FM) coupling in the deep bulk layers, in pristine CrI₃ crystals below the Curie temperature. In this study, we used Ni thin film deposition to tune the surface magnetic states in bulk CrI₃. A nanometer thickness (4 nm thick) of Ni was deposited on the surface of CrI₃ using electron-beam evaporation to form a Ni/CrI₃ heterostructure. The deposited Ni thin layer forms nanoclusters that completely cover the CrI₃ surface. Magnetic states of CrI₃ before and after Ni deposition are probed by ultralow-frequency magneto-Raman spectroscopy. Instead of seeing three spin wave branches in Raman scattering below 2 T, as in pristine bulk CrI₃, in Ni/CrI₃, we observe only a single spin wave branch, which is softened compared to that in pristine CrI₃ and displays a Zeeman shift under an out-of-plane magnetic field up to 7 T. This observation reveals that the AFM layers on pristine CrI₃ crystal surfaces transit into FM layers, so the entire CrI₃ crystal is in the FM state after Ni deposition. First-principles calculations show that Ni atoms tend to diffuse into the CrI₃ lattice, and the FM interlayer coupling has a much lower energy than AFM coupling in the presence of Ni atoms. As a result, our studies show that the magnetic state of CrI₃ can be modified through deposition of a thin metal layer on the surface, offering a route for controlling the spin degree of freedom in van der Waals magnets.

• Research Organization: Texas Tech University, Lubbock, TX (United States); The University of Texas at Dallas, Richardson, TX (United States); Towson University, MD (United States); University of Northern Iowa, Cedar Falls, IA (United States)
• Sponsoring Organization: Air Force Office of Scientific Research (US AFOSR); NSF Expanding Capacity in Quantum Information Science and Engineering (ExpandQISE); National Science Foundation (NSF); Office of Naval Research (ONR); USDOE Office of Science (SC)
• Grant/Contract Number: SC0020334
• OSTI ID: 2574561
• Journal Information: ACS Applied Nano Materials, Journal Name: ACS Applied Nano Materials Journal Issue: 5 Vol. 8; ISSN 2574-0970
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English

Related Subjects

CrI3
Ni thin film
Raman spectroscopy
crystals
deposition
first-principles calculation
layers
magnetic properties
quantum mechanics
spin wave
van der Waals magnet