Laboratory for the physics of transport phenomena

Laboratory equipment

Experimental setups

Conventional

New or under finalization

& Selected results

Thermopower and electrical resistivity

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Thermopower and electrical resistivity are measured simultaneously in the temperature interval from 2 to 300 K.
 

The thermopower is measured using differential method which gives thermopower of the sample without the need to calculate thermal gradient across the sample. For the thermopower measurement two chromel – gold with 0.07 % Fe thermocouples with 50 μm wires were used. Thermal gradient was achieved with two 1 kΩ RuO2 chip-resistors – one on each side of the sample (they were switched off and on alternately to produce thermal gradients in both directions of the sample). Gold wires of the thermocouples for the thermopower measurements were used as the voltage terminals in the electrical resistivity measurement.

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High temperature resistivity is measured using standard four probe method and a Carbolite furnace (1300 K) with a Eurotherm 3216 controller.
 

Samples were placed on a ceramic holder and connected to the gold wires by silver epoxy DuPont 6838.

Thermal conductivity

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Thermal Conductivity κ is measured in the temperature interval from 2 to 300 K in liquid helium cryostat.
 

The samples investigated are rod-shaped and one-dimensional approximation is assumed.
 

We use an absolute steady-state heat-flow method. The thermal flux through the sample is generated by a 1 kΩ RuO2 chip-resistor, glued to one end of the sample, while the other end is attached to a copper heat sink. For good thermal contacts and electrical isolation IMI 7031 varnish is used. The temperature gradient across the sample is monitored by a chromel – (gold+0.07 at.% Fe) differential thermocouple with the wires-diameter of 25 μm.

Hall effect

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The Hall effect measurements are performed by a standard AC technique and by a five point method.
 

The magnetic fields up to 1 T are produced by a conventional electromagnet.
 

The resolution is 1 nV in the Hall voltage
 

The measurements are performed in the temperature interval from 90 to 370 K.
 

For the analysis of the Hall effect in magnetic materials we use the results for the magnetic properties obtained by our collaborators from the other institutions (see page Collaboration: Informal International Collaboration)

New

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Magnetic fields up to 10 T

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Measurements in magnetic field are performed using a superconducting magnet from Oxford Instruments. Magnet is capable of reaching magnetic field of 8 T if cooled to 4.2 K by liquid helium. Field of 10 T can be reached if the helium surrounding the magnet is pumped and thus cooled to 2.1 K. The magnet is equiped with variable temperature insert (VTI) from the same company.

Experimental set up is now completed for electrical resistivity (magnetoresistivity) and thermal conductivity measurements. Some details of the methods for measurements of this properties are given abowe on this page.

For testing the new setup, first resistance measurements under high magnetic field have been made on a well known superconductor 2H-NbSe2 , and the effect of field is shown in the picture below.

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Archive pictures from the building of the equpment

Archive

High Pressure

Pressures:

0 - 3 GPa
in Pyston Cylinder pressure cell

0 - 10 GPa (and higher under the way)
in DAC (Diamond Anvil Cell)

Temperatures: 1.5 – 300 K

 

Magnetic fields: 0 – 10 T

Details:
Building of the high pressure facilities was a part of the UKF Project (1B # 65/10) and the details can be found on the project´s pages.

UKF

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Influence of hydrostatic pressure on inplane resistivity of Co0.33NbS2

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A note

Great skill for the preparation of electrical contacts with the help of the microscope is still required.

Selected results

Anisotropic thermopower and electrical resistivity of o-Al13Co4 single crystal along different crystalline directions

Electrical resistivity ρ of Ba(Fe0.92Co0.08)2As2 and Ba(Fe0.95Ni0.05)2As2 as a function of temperature, and electrical resistivity ρN, which originates from the narrow band and exhibits a hidden Fermi-liquid behavior, as a function of T2.

Anisotropic thermal conductivity and extracted fonon contribution of o-Al13Co4 single crystal along different crystalline directions

Anisotropic Hall RHceofficient of two single crystals of complex metallic alloys with magnetic field paralel2 to crystalline a(a*), b and c axes

More results
        and
        still open questions →

Institute of Physics, Zagreb, 2013.