Since 1944 when Ye. K. Zavoisky performed the first electron paramagnetic resonance (EPR) experiments in Kazan (USSR), there was vast development in the field of magnetic resonance.¹  Probably one of the most significant advances in EPR was achieved by increasing the operating microwave (mw) frequency and corresponding spectrometer's static magnetic field, which enables accurate studies of paramagnetic species that would not be accessible at low fields (see, e.g. Fig. 1). In 1957, G. Feher foresaw such importance of increasing the irradiation frequency to enhance both sensitivity and resolution of EPR spectrometers.²  However, it took a few decades...