Submillimeter wave ESR system in Kobe University is presented. It covers the frequency region from 60 to 383GHz and can apply the pulsed magnetic field up to 30T. The measurement of Y2Cu2O5 single crystals using our system is presented.

Submillimeter wave ESR measurements of metamagnetic Y2Cu2O5

EPR and AFMR of Li 2 CuO 2 in Submillimeter Wave Region

New systems for millimeter and submillimeter wave ESR have been developed in Kobe University. In the previous system the pulsed magnetic field was limited up to 17 T in the temperature range from 1.8 to 86 K. Using the new systems, we can measure in the field range up to 30 T in the temperature range from 1.8 K to 4.2 K and from 18 K to room temperature. The resolution of the magnetic field has been also improved in the new ESR system. The details of our new ESR systems are presented. In addition, the measurements of Yb2Cu2O5 using these new systems are presented.

Millimeter and Submillimeter Wave ESR System: Using 30 T Pulsed Magnetic Field

High field ESR measurements of Cu 3 (CO 3 ) 2 (OH) 2 have been performed in the frequency region from 50 to 900 GHz and in the temperature region from 1.8 to 265 K using the pulsed magnetic field up to 36 T. The large g -shifts below 23 K and the characteristic temperature dependence of the linewidth are discussed in connection with the two maxima of magnetic susceptibility observed at 5 and 23 K. Our ESR results together with the magnetization and theoretical results suggest that the ground state of the system is in the spin fluid (SF) phase at low field and low temperature. From the frequency–field dependence measurements at 1.8 K, the direct transition, which is closely related to the magnetization plateau from 16 to 26 T at 1.5 K, is observed for the first time. The observed frequency–field diagram suggests that the exchange interaction in the dimer is estimated to be about 50 K (1057 GHz).

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High Field ESR Study of the S=1/2 Diamond-Chain Substance Cu3(CO3)2(OH)2 up to the Magnetization Plateau Region

The development of a high frequency electron spin resonance (ESR) spectrometer with a wide frequency range using a gyrotron as the radiation power source is described. GYROTRON FU-E, optimized for use in an ESR spectrometer in the millimeter wave range, was developed in Fukui University. In order to test the normal operation of the spectrometer, the ESR of two standard samples, single crystal and polycrystalline DPPH, has been measured, in the pulsed mode over the frequency range from 65 GHz to 135 GHz.

ESR spectrometer with a wide frequency range using a gyrotron as a radiation power source

We found new effect which changes g-values of pair and trimer Co2+ spins by EPR of Rb2Co0.3Mg0.7F4 at 220, 370, 762.2 and 693.6 GHz in pulsed high magnetic fields. The anomalous g-values come from mixing of 1LS and strong exchange interaction.

Naoki Maki

Papers

Submillimeter EPR of Co:Rb2MgF4 and anomalous g-values