We have performed high-field electron spin resonance (ESR) measurements of the isolated antiferromagnetic dimer system Na2Co2(C2O4)3(H2O)2 by illuminating circularly polarized microwaves at 162 GHz. Different from a usual ESR signal by the magnetic dipole transition, the resonance signal, coming from the direct transition between the singlet and triplet states in this compound, is suggested to show absence of circular dichroism. From this curious behavior, we consider that the direct transition in Na2Co2(C2O4)3(H2O)2 is driven by oscillating electric fields of microwaves. We propose that the spin current mechanism is responsible to induce a finite probability for the electric-dipole-active transition between the singlet and the triplet states in Na2Co2(C2O4)3(H2O)2.
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics