Development of High-Field and High-Pressure ESR System and Application to Triangular Antiferromagnet $$hbox {CsCuCl}_{3}$$ CsCuCl 3

We have developed a new hybrid-type pressure cell for the high-pressure and high-field electron spin resonance (ESR) measurement using a widely used Oxford 15 T superconducting magnet with the variable temperature insert (VTI). The size of the pressure cell was optimized and a probe was also specially designed so as to be fitted to the VTI. We confirmed that the new pressure cell can generate the pressure up to at least 2.0 GPa repeatedly. Using this new ESR system, high-pressure and high-field ESR measurement was performed on the triangular antiferromagnet $$\hbox {CsCuCl}_{3}$$ for $$H \parallel c$$ at 4.2 K in the frequency region 60 GHz–420 GHz. We succeeded in observing the significant pressure effect of this compound. Moreover, a new ESR mode which is expected to correspond to the 1/3 magnetization plateau was observed at 0.80 GPa.