arXiv:1001.0454v1 [cond-mat.str-el] 4 Jan 2010 APS/123-QED Evaluations of pressure-transmitting media for cryogenic experiments with diamond anvil cell ∗ Naoyuki Tateiwa † and Yoshinori Haga Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Naka, Ibaraki 319-1195, Japan (Dated: October 13, 2018) The fourteen kinds of pressure-transmitting media were evaluated by the ruby fluorescence method at room temperature, 77 K using the diamond anvil cell (DAC) up to 10 GPa in order to find ap- propriate media for use in low temperature physics. The investigated media are a 1:1 mixture by volume of Fluorinert FC-70 and FC-77, Daphne 7373 and 7474, NaCl, silicon oil (polydimethyl- siloxane), Vaseline, 2-propanol, glycerin, a 1:1 mixture by volume of n -pentane and isopentane, a 4:1 mixture by volume of methanol and ethanol, petroleum ether, nitrogen, argon and helium. The nonhydrostaticity of the pressure is discussed from the viewpoint of the broadening effect of the ruby R$_{1}$ fluorescence line. The R$_{1}$ line basically broadens above the liquid-solid transition pressure at room temperature. However, the nonhydrostatic effects do constantly develop in all the media from the low-pressure region at low temperature. The relative strength of the nonhydrostatic effects in the media at the low temperature region is discussed. The broadening effect of the ruby R$_{1}$ line in the nitrogen, argon and helium media are significantly small at 77 K, suggesting that the media are more appropriate for cryogenic experiments under high pressure up to 10 GPa with the DAC. The availability of the three media was also confirmed at 4.2 K. PACS numbers: I. INTRODUCTION The development of the diamond anvil cell (DAC) has revolutionized high-pressure research in various scientific fields such as physics, chemistry, geophysics, materials science and biology [1, 2]. Various types of experiments can be performed with the DAC. For instance, X-ray diffraction experiments, optical absorption and reflectiv- ity measurements, Raman and Brillouin scattering stud- ies, and transport and thermal measurements under high pressure above 10 GPa have become possible. These methods have been successfully applied in low temper- ature physics where many interesting pressure-induced phenomena such as superconductivity have been exten- sively studied [3, 4]. In high-pressure experiments, nonhydrostatic effects such as inhomogeneous pressure distribution (pressure gradient) and uniaxial (deviatoric) stress need to be re- duced because the effects can strongly influence the phys- ical state of a sample. It is important to use a pressure- tranmistting medium in a pressure region where it is in a liquid state. However, a liquid medium solidifies through a liquid-solid transition on cooling from room tempera- ture. The shear stress of a solid medium causes nonhy- drostatic pressure in the low temperature region. The purpose of the present study is to evaluate the pressure-qualities of media used in low temperature physics, and in particular for the strongly correlated elec- tron system in which novel types of physical phenomena such as non-Fermi liquid behavior or unconventional su- $^{∗}$Review of Scientific Instruments 80 , 123901 (2009) $^{†}$Electronic address: tateiwa.naoyuki@jaea.go.jp The fourteen kinds of investigated media are a 1:1 mixture by volume of Flourinert FC-70 and FC-77 (Flourinert FC70/77, Sumitomo 3M), Daphne 7373 and 7474 (Idemitsu Kosan), NaCl, Vaselin, silicon oil (polydimethylsiloxane with a kinematic viscosity of 1 mm $^{2}$· s − $^{1}$, Shin-Etsu Chemical), 2-propanol, glycerin, 1:1 mixture by volume of n -pentane and isopentane (pen- tane mixture), a 4:1 mixture by volume of methanol and ethanol (4:1 M-E mixture), petroleum ether (Wako Chemical Industries), nitrogen, argon and helium. The II. EXPERIMENTAL Most of previous studies on pressure-media have con- cerned the hydrostaticity of the pressure at room tem- perature [10–13]. Very few studies have been carried out on the pressure-qualities of media in the low temperature region up to 3 GPa [14, 15]. In this study, therefore, the fourteen kinds of pressure-transmitting media were stud- ied by the ruby fluorescence technique up to 10 GPa at room temperature, 77 and 4.2 K. perconductivity have been extensively studied [5, 6]. The electronic state of the system is generally sensitive to small amounts of impurities or nonhydrostatic effects. A recent example is the case of the “FeAs-based supercon- ductor” CaFe 2 As 2 in which superconductivity was dis- covered above 0.5 GPa in high-pressure studies using or- ganic media [7, 8], while it was not observed with a he- lium medium [9]. This discrepancy may result from sen- sitive structural instability to the uniaxial stress of the compound. nonhydrostatic effects cannot be avoided in the low temperature region. It is necessary to compare quantitatively the strength of the nonhydrostatic effects of various kinds of pressure-media.