High-frequency ESR measurements using pulsed magnetic fields in Kobe

Recent development of the high-field facility in Kobe University is presented. We installed a 3 kV, 100 kJ capacitor bank, this is four times larger in energy than the previous one, and we achieved 42 T recently using a Cu-Ag pulsed magnet. Recent high-field ESR studies of quantum spin systems such as high pressure phase (VO)₂P₂O₇ will be presented. The high-pressure phase of (VO)₂P₂O₇ is the S = 1/2 bond alternating antiferromagnet; we found an anomaly in the ESR mode of the high-pressure phase (VO)₂P₂O₇ single crystal at 20 T by observing the frequency dependence at 4.2 K. Finally, we refer to our new development of the high-field ESR system under high pressure. We developed a compact pressure cell with sapphire window which fits into our pulsed magnet. The ESR result using this pressure cell will be presented.