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

Abstract

We have developed a new hybrid-type pressure cell for the high-pressure and high-field 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 GPa repeatedly. Using this new ESR system, high-pressure and high-field ESR measurement was performed on the triangular antiferromagnet CsCuCl 3 for H ∥ c at 4.2 K in the frequency region 60 GHz to 420 GHz. We succeeded in observing the significant pressure effect of this compound.

High-Pressure THz ESR

“…We developed systems that combined this pressure cell with a cryogen-free superconducting magnet with a maximum magnetic field of 10 T (abbreviated as 10T-CSM later) (2015) [16] and a cryogen-free superconducting magnet with a maximum magnetic field of 25 T (25T-CSM) (2018) [17]. In addition, we developed a system, where a slightly smaller pressure cell and a 15 T superconducting magnet (15T-SM) were combined (2019) [18]. The details of these systems will be described later.…”

“…Although the maximum pressure is slightly reduced (2.0 GPa), we also use the smaller outer diameter (23.5 mm) with the same inner diameter [Fig. 2 (b)] [18]. In both cases, the sample space inside the Teflon capsule before applying the load is 4 mm ×11 mm.…”

“…In addition to these systems, we also developed a system combined with 15T-SM, which used a reflection approach that was similar to that of the 25T-CSM system [18]. The pressure cell has a slightly smaller outer diameter (23.5 mm) as shown in Fig.…”

“…4.3 Hexagonal ABX 3 -type antiferromagnet CsCuCl 3 [18] This is an example of using the 15T-SM high-pressure ESR system. CsCuCl 3 (magnetic ion Cu 2+ , S = 1/2) is a well-known substance, which shows a remarkable quantum effect [44].…”

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

“…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. For example, we observed the pressure-induced quantum phase transition from the dimer singlet state to the plaquette singlet state in the two-dimensional orthogonal dimer spin system SrCu 2 (BO 3 ) 2 [37], the novel magnetic phases under pressure and high magnetic field in the triangular lattice antiferromagnet Cs 2 CuCl 4 [38], anomalies in the antiferromagnetic resonance mode corresponding to the 1/3 magnetization plateau in the hexagonal ABX 3 -type antiferromagnet CsCuCl 3 [39], and so on. On the other hand, KCuCl 3 , which is of interest in this paper, has not been studied sufficiently around the critical pressure from the microscopic point of view, as mentioned above.…”