Laboratory of high pressure physics

Instrumentation development in our group plays a vital role in the research of material properties under extreme conditions. Number of high pressure cells has been designed and built in the High Pressure Laboratory to study the magnetic, transport and thermodynamic properties of materials under high pressures, low temperatures and high magnetic fields.

Piston-cylinder cell for the SQUID magnetometry is shown in Fig.1. Pressure cell provides large sample volume (~10mm³) for experiments under pressures up to ~1.2GPa, allowing the excellent sensitivity of measurement and detailed investigation of magnetic properties of measured samples in this pressure region. For accessing higher pressures ~ 10 GPa in SQUID experiments, the diamond anvil cell (Fig. 2) has been built recently. The cell geometry has been optimized to reduce its background signal, partially compensating the small sample volume. Both types of pressure cells are based on non-magnetic CuBe alloys.

Fig.1. CuBe piston-cylinder cell for SQUID magnetometer, 1) upper clamping bolt, 2) plug, 3) plug sealing rings, 4) sample, 5) cell body, 6) lead manometer, 7) piston, 8) piston backup, 9) lower clamping bolt.

Fig.2. DAC pressure cell for the SQUID magnetometer: 1) body of the cell, 2) bottom locking nut, 3) springs, 4) piston-guide for the diamond anvils, 5) gasket, 6) diamond anvils, 7) highly polished zirconia ceramic washer with a MoS lubricant, 8) position lock for the upper spring.

In addition, the double-layered CuBe/NiCrAl piston-cylinder cell (Fig. 3) for experiments within the PPMS apparatus (Quantum Design) has been acquired. The limit for the pressure is 3GPa, feedthrough with 12-16 electrical leads allows measurement of electrical resistivity, magnetoresistance and Hall effect (default setting), AC susceptibility (custom built detection coils) and heat capacity (AC calorimetry) under high pressures in the temperature region 2-400K and magnetic fields up to 14T. Recently, Merryll-Bassett type DAC (fig.4) has been built in our lab to extend the range of the transport measurements in PPMS14 to pressures up to ~ 10GPa. Additionally, both PPMS – based pressure cells can be used in the dilution refrigerator in the Joint laboratory for magnetic studies (JLMS link), extending the accessible temperature region down to ~ 50mK and magnetic fields up to 15T.

Fig.3. Double layered CuBe/NiCrAl piston-cylinder pressure cell for the PPMS. 1- body of the cell, 2a-plug, 2b-plug with sealed Cu wires, 3-CuBe sealing rings, 4-PTFE capsule, 5-nonmagnetic WC piston, 6-upper clamping bolt with the WC piston support, 7-lower clamping bolt with the WC plug back-up, 8-modified PPMS puck, 9-WC rod for applying the load in the hydraulic press.

Fig.4. DAC pressure cell for transport measurements in the PPMS.

Helium refrigerator cryostat

The helium refrigerator - cryostat completed with a set of high pressure Cu-Be pressure cells. This equipment enables to measure susceptibility, transport properties, compressibility and elongation in the pressure range of 15 kbar and a temperature interval from 4 to 320 K.

Fig.5. Helium refrigerator - cryostat completed with a high pressure cell.

The Magnetic Property Measurement System

The Magnetic Property Measurement System (MPMS XL 7T) offers advanced performance in all areas of magnetometry. It can be used for basic characterization of magnetic properties of all kinds of materials. Studies can be performed in magnetic field up to 7 Tesla in temperature range 1.9 – 400 K (with furnace up to 800 K) in the range of magnetization up to 5 emu with sensitivity 10-8 emu. Most of the materials can be studied under hydrostatic pressure up to 1.2 GPa and under uniaxial pressure up to the elastic limit.

Fig.6. The Magnetic Property Measurement System.

Multifunctional Measurement Instrument

The MMI (Multifunctional Measurement Instrument) represents laboratory equipment with an open architecture, variable temperature-field system, designed for variety of physical property measurements. The device is uniquely equipped with the direct magnetocaloric measurement of adiabatic temperature change of a sample with respect to magnetic field change as fast as 12 Ts^-1. Other measurement options are represented by resistivity, magneto-resistivity and AC magnetic susceptibility measurement. Sample environment controls include magnetic field up to 5 T, temperature control in range from 80 K to 800 K and hydrostatic pressure up to 1.5 GPa (in temperature range from 80 K to 700 K), for details see above.

Fig.7. The MMI in configuration for direct measurement of magnetocaloric effect.