Development and application of 2.5 GPa–25 T high-pressure high-field electron spin resonance system using a cryogen-free superconducting magnet

Abstract

We have developed a high-pressure electron spin resonance probe and successfully installed into the world's highest-field cryogen-free superconducting magnet having a maximum central field of 24.6 T. The high pressure of 2.5 GPa is achieved by the specially designed piston-cylinder pressure cell using THz-wave-transparent components. In the first application of this high-pressure high-field ESR system, we observed that the orthogonal dimer spin system SrCu(BO) undergoes a quantum phase transition from the dimer singlet ground to the plaquette singlet ground states.

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

“…Therefore, its design can be optimized to match the upper limit of the toughness of the ceramics. The light pipe of 9ϕ and the same sample space (5ϕ× ∼ 10 mm) are required to keep the sensitivity [6], while the whole probe is inserted into an insert pipe chamber with the outer diameter of 35 mm with the He exchange gas [ Fig. 1 (a)].…”

“…The details are found in Refs. [4,6]. Gunn oscillators and backward traveling wave oscillators (BWOs) are used.…”

“…Recently, novel pressure-induced phases have attracted much attention and been studied intensively especially in quantum magnets. So far we have developed high-pressure and high-field ESR systems and applied them to quantum magnets [1][2][3][4][5][6]. We use a transmission technique in our ESR systems and we have developed specially designed piston-cylinder type pressure cells using ceramics inner parts which have good transmittance to millimeter and submillimeter waves.…”

“…Although this propagation way of the electromagnetic wave is more lossy as compared with the previous 10 T system with no reflection point from top to the detector [4], we confirmed that the sensitivity is unchanged or more improved by the use of the commercial InSb detector. Using this technique, we succeeded in performing ESR measurement with the world highest cryogen-free superconducting magnet up to 25 T in the user facility of Tohoku University [6].…”

First ESR Detection of Higgs Amplitude Mode and Analysis with Extended Spin-Wave Theory in Dimer System KCuCl$$_3$$

“…The high-pressure ESR is a very powerful means to know the spin states of magnetic materials under pressure. In particular, the recently developed our broadband high-pressure ESR system in the THz region has features of high pressure up to 2.5 GPa and a wide frequency range up to 0.8 THz [35,36]. These features are very useful for observing pressure changes in the ground state and the low-lying excited states of quantum magnets, because the THz region matches their energy levels of the low-lying excited states.…”