Tracking Polar Mesospheric Clouds Using Unbinned Correlation Methods

We are experimenting with a correlation method that allows us to cross-correlate images that have geolocated pixels without having to bin the pixels and lose resolution. In addition to preserving resolution, this correlation method also allows us to perform transformations on the images that would be difficult to perform with other correlation methods. We are working on this correlation method in order to use cross-correlations to track polar mesospheric clouds (PMCs) using the data from the Cloud Imaging and Particle Size (CIPS) instrument on the Aeronomy of Ice in the Mesosphere (AIM) satellite

Fundamental Spin Interactions Underlying the Magnetic Anisotropy in the Kitaev Ferromagnet CrI3_3

We lay the foundation for determining the microscopic spin interactions in the two-dimensional (2D) ferromagnets by combining our angle-dependent ferromagnetic resonance (FMR) experiments on high quality CrI$_3$ single crystals with theoretical modeling based on symmetries. In the 2D limit, ferromagnetism is stabilized by magnetic anisotropy. We find the largest anisotropy arises from Kitaev interactions of strength $K~\sim-5.2$ meV, larger than the Heisenberg exchange $J~\sim-0.2$ meV. We further discover that the symmetric off-diagonal anisotropy $\Gamma\sim-67.5$ $\mu$eV, though small, plays the crucial role of opening a gap in the magnon spectrum and stabilizing ferromagnetism in the 2D limit. The resolution of the FMR data is sufficient to reveal a $\mu$eV-scale quadrupolar contribution in the $S=3/2$ magnet. Our identification of the interactions underlying ferromagnetism and exchange anisotropies opens paths towards 2D ferromagnets with higher T_\rm{C} and magnetically frustrated quantum spin liquids based on Kitaev physics.Comment: 5 pages, 4 figure

Distinct magneto-Raman signatures of spin-flip phase transitions in CrI3_{3}

The discovery of 2-dimensional (2D) materials, such as CrI$_{3}$, that retain magnetic ordering at monolayer thickness has resulted in a surge of both pure and applied research in 2D magnetism. Here, we report a magneto-Raman spectroscopy study on multilayered CrI$_{3}$, focusing on two additional features in the spectra that appear below the magnetic ordering temperature and were previously assigned to high frequency magnons. Instead, we conclude these modes are actually zone-folded phonons. We observe a striking evolution of the Raman spectra with increasing magnetic field applied perpendicular to the atomic layers in which clear, sudden changes in intensities of the modes are attributed to the interlayer ordering changing from antiferromagnetic to ferromagnetic at a critical magnetic field. Our work highlights the sensitivity of the Raman modes to weak interlayer spin ordering in CrI$_{3}$

Distinct magneto-Raman signatures of spin-flip phase transitions in CrI3

The discovery of 2-dimensional (2D) materials, such as CrI3, that retain magnetic ordering at monolayer thickness has resulted in a surge of research in 2D magnetism from both pure and applied perspectives. Here, we report a magneto-Raman spectroscopy study on multilayered CrI3, focusing on two new features in the spectra which appear at temperatures below the magnetic ordering temperature and were previously assigned to high frequency magnons. We observe a striking evolution of the Raman spectra with increasing magnetic field in which clear, sudden changes in intensities of the modes are attributed to the interlayer ordering changing from antiferromagnetic to ferromagnetic at a critical magnetic field. Our work highlights the sensitivity of the Raman modes to weak interlayer spin ordering in CrI3. In addition, we theoretically examine potential origins for the new modes, which we deduce are unlikely single magnons