Date of Award
Master of Science
Srinivasa Rao Singamaneni
Broadening the knowledge and understanding on the magnetic correlations in van der Waals layered magnets is critical in realizing their potential next-generation applications in devices such as spintronics. In this study, we employ high frequency (ν = 120 GHz, 240 GHz) electron spin resonance (ESR) spectroscopy on plate-like CrX3 (where X = Cl, Br, I) to gain insight into the magnetic interactions as a function of temperature (200 – 4.4 K) and the angle of rotation θ (degrees). We find that the temperature dependence of the ESR linewidth is well described by the Ginzburg-Landau critical model, indicative of antiferromagnetic correlations and the presence of two-dimensional (2D) correlations. Furthermore, our findings show that the resonance field in CrX3 follows a (3cos2��−1)-like angular dependence, while the linewidth follows a (3cos2��−1)2-like angular dependence, a behavior indicative of 2D correlations that is likely due to the interaction of the external magnetic field applied during the ESR experiment. The external magnetic field presumably induces an interaction between the long-range spin vortices and spin clusters that may have formed during magnetic phase separation, as evidenced from the bifurcation between zero-field- and field-cooled temperature dependent magnetic susceptibility measurements performed on CrBr3, further confirming the coexistence of antiferromagnetism and ferromagnetism in the bulk compound. Frequency dependent ESR measurements performed on CrCl3 shows a frequency dependence of the ESR linewidth and BKT transition temperature, TBKT, indicative of magnetic field induced behavior in the system. This study demonstrates the significance of employing spin sensitive techniques such as ESR to better understand the magnetic correlations in similar van der Waals magnets.
Received from ProQuest
Saiz, Christian, "High Frequency Electron Spin Resonance Investigations On Quasi-Two-Dimensional Chromium Halide Magnets" (2021). Open Access Theses & Dissertations. 3344.