Optical Studies of RuO2 Thin Films

Rutile RuO2 was proposed as a textbook room temperature d-wave altermagnet because of its predicted large non-relativistic spin splitting. However, recent results on bulk crystals and epitaxial thin films suggest that bulk RuO2 doesn't magnetically order. Instead, it's proposed that thin films may magnetically order under the right strain and chemical potential. Here, I'll present our optical magnetic circular dichroism and second harmonic generation measurements on RuO2 thin films to study their magnetic and crystal structure. Our results suggest the properties of RuO2 thin films aren't intricately linked to sample thickness, further highlighting the need to fully characterize RuO2 thin films.