Development of High-Field ESR System Using SQUID Magnetometer and its Application to Measurement under High Pressure

Abstract

We have developed a high-field and high-frequency ESR system using a commercially available magnetometer equipped with the superconducting quantum interference device (SQUID). This is magnetization detection type ESR and ESR is observed as a change of the magnetization at the resonance condition under irradiation of the electromagnetic wave. The frequency range is from 70 to 315 GHz and the maximum magnetic field is 5 T. The sensitivity is estimated to be 10 13 spins/G. The advantage of this system is that the high-field ESR measurements can be made very easily and quantitatively. Moreover, this high-field ESR can be applied to the measurements under pressure by using a widely used piston-cylinder pressure cell.

Electron paramagnetic resonance spectroscopy using a direct current-SQUID magnetometer directly coupled to an electron spin ensemble

“…Recently, metallic coplanar waveguides are also used 6 to perform on-chip ESR spectroscopy in wider temperature and magnetic field range. On the other hand, EPR spectroscopy has also been performed with a pickup coil and a direct current superconducting quantum interference device (dc-SQUID) amplifier 7,8 . In this method, the change of magnetization induced by EPR is detected by a pickup coil and the information is transferred to the dc-SQUID amplifier placed far from the sample to avoid high magnetic fields.…”

Frequency Extension to the THz Range in the High Pressure ESR System and Its Application to the Shastry–Sutherland Model Compound SrCu2(BO3)2

“…However, the ZrO 2 -based ceramic does not have enough transmission especially for the higher frequency region. 1,[16][17][18][19][20][21][22] In order to achieve the higher pressure and the wider frequency measurement simultaneously, finding a new material for the inner parts is an important factor. The ZrO 2 -based ceramic, which is known as the partially stabilized zirconia, is believed to have particular fracture toughness as compared with other ceramics in general.…”

“…Therefore, our high-pressure ESR systems have proved to be one of the most powerful means to study quantum spin systems. 1,[5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] So far, we developed the pressure cell with the moderate pres- Phase diagram for the Shastry-Sutherland model. 26 sure range below 1 GPa and the wide frequency region from 70 to 700 GHz, [5][6][7][8][9][10][11][12][13][14][15] and that with the higher pressure range up to 1.5 GPa and the limited frequency region from 70 to 400 GHz.…”

“…26 sure range below 1 GPa and the wide frequency region from 70 to 700 GHz, [5][6][7][8][9][10][11][12][13][14][15] and that with the higher pressure range up to 1.5 GPa and the limited frequency region from 70 to 400 GHz. 1,[16][17][18][19][20] Recently, we also developed a hybrid-type pressure cell with larger sample space and higher pressure region for large bore magnet, which covers the frequency region form 50 to 400 GHz and the pressure up to 2.5 GPa. 21,22 In order to achieve the high pressure and the wide frequency region simultaneously, the key factors are the toughness and the transmission property of the inner parts of the pressure cell.…”

“…On the other hand, in our systems, the frequency can be varied very widely, which includes the so-called THz region defined as the frequency region from 0.1 to 10 THz, since we simply combine the piston–cylinder pressure cells with the transmission-type high-field ESR system using the pulsed high magnetic field − or the static magnetic field. ,− The most characteristic point of our pressure cell is that all inner parts are made of sapphire and ZrO 2 -based ceramic. They have both the toughness and the transmission in the THz region, and this enables us to observe the transmitted light through the pressure cell in the wide frequency region.…”