Abstract
The research on layered van der Waals (vdW) magnets is rapidly progressing owing to exciting fundamental science and potential applications. In bulk crystal form, CrCl3 is a vdW antiferromagnet with in-plane ferromagnetic ordering below 17 K, and CrI3 is a vdW ferromagnet below 61 K. Here, we report on the electron spin resonance (ESR) properties of CrCl3 and CrI3 single crystals upon photo-excitation in the visible range. We noticed remarkable changes in the ESR spectra upon illumination. In the case of CrCl3, at 10 K, the ESR signal is shifted from g = 1.492 (dark) to 1.661 (light), the linewidth increased from 376 to 506 Oe, and the signal intensity is reduced by 1.5 times. Most interestingly, the observed change in the signal intensity is reversible when the light is cycled on/off. We observed almost no change in the ESR spectral parameters in the paramagnetic phase (>20 K) upon illumination. Upon photo-excitation of CrI3, the ESR signal intensity is reduced by 1.9 times; the g-value increased from 1.956 to 1.990; the linewidth increased from 1170 to 1260 Oe at 60 K. These findings are discussed by taking into account the skin depth, the slow relaxation mechanism, and the appearance of low-symmetry fields at the photo-generated Cr2+ Jahn-Teller centers. Such an increase in the g-value as a result of photo-generated Cr2+ ions is further supported by our many-body wavefunction calculations. This work has the potential to extend to monolayer vdWs magnets by combining ESR spectroscopy with optical excitation and detection.
Original language | English |
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Article number | 082406 |
Journal | Applied Physics Letters |
Volume | 117 |
Issue number | 8 |
DOIs | |
State | Published - Aug 24 2020 |
Funding
S.R.S. and L.M.M. acknowledge support from a UTEP start-up grant. L.M.M. acknowledges the NSF-LSAMP BD fellowship. Crystal growth and characterization at the Oak Ridge National Laboratory (M.A.M.) was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. J.N. and O.G.P. gratefully acknowledge support from the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences, through the Argonne National Laboratory under Contract No. DE-AC02-06CH11357. R.Y. was supported by the Sinergia Network NanoSkyrmionics (Grant No. CRSII5-71003). M.P. was supported by the Swiss National Science Foundation (Grants Nos. 162612 and 172543). Calculations were performed at the Swiss National Supercomputing Centre (CSCS) under Project No. s832.