DC Magnetoresistance and High-pressure Resistivity Measurements

Specification, General Description

[Photo: Uni Stuttgart]

Figure 1: Setup overview (top), cryostat sketch (bottom left) and magnet photo (bottom right).
Photo: PI1 Uni Stuttgart
Photo: PI1 Uni Stuttgart

Specification

Temperature He bath cryostat: 4.2 K - 300 K (2.5 K with pumping) 
Magnetic fields Oxford IPS 120: up to 6.5 Tesla (Reversible)
Pressure

Easylab Pcell: up to 30 kbar
Rotation Uniaxial 360°
Optimum measurement value 10-9 - 106 Ωcm

General Description

Even though it sounds classics, resistivity measurements have always been and still are a powerful technique to study the nature of materials. Introduced by the German physicist Georg Ohm in early 1800s, this method has been vastly developed since then. The idea itself is simple: one applies current and measures voltage or vice versa. In our lab, a multi-purpose resistivity measurement setup has been developed utilizing a He cryostat (Figure 1). With this setup, we have been able to investigate the electronic properties of many exotic materials, ranging from Mott-insulators to topological semimetals. Our setup allows us to go down to 4.2 K and, with pumping, to 2.5 K. Additionally, magnetic field of up to 6.5 T can be applied. There are two sample holders available, one of them for magnetoresistance, the other one for high-pressure measurements. With this setup we can measure resistivity from 10-9 to 10 6 Ωcm with high precision.

DC Magnetoresistance and High-Pressure Measurements Configuration

 

Depending on the sample, 2 or 4 contact measurement techniques can be utilized. In total, there are 8 pins that can be used (Figure 2). The sample holder itself can be used to mount samples from 5 mm down to 100 micron in size. Since we have 3 nanovoltmeters, 3 measurements can be done simultaneously. The sample holder itself is 360° rotatable; with this, measurement error due to the alignment can be minimized. We can arrange the setup for the measurements of longitudinal and transversal magnetoresistance, as well as for Hall measurements.

Figure 2: Magnetoresistance configuration (left) and a typical sample (right).
Photo: PI1 Uni Stuttgart
Figure 3: High pressure parts: the pressure setup overview (top), a sketch of the pressure cell (middle) and a feedtrough with a sample (buttom).
Photo: PI1 Uni Stuttgart

With this setup, we are able to reveal important properties of the samples studied including, magnetoresistance (Figure 4), charge concentration and mobility (Figure 5), gap opening (Figure 6) and Hall resistance (Figure 7).

Figure 4: Magnetoresistance of YbPtBi [1]. ----- Figure 5: Carrier concentration and mobility of YbPtBi [1].
Figure 6: Gap opening in Weyl semimetal NbP [2]. --- Figure 7: Hall resistance and Hall conductivity in YbPtBi [1].
Figure 8: Metal-insulator transition in a kappa-type BEDT-TTF organic conductor [3].

References:

[1] M. B. Schilling, A. Löhle, D. Neubauer, C. Shekhar, C. Felser, M. Dressel, and A. V. Pronin, Phys. Rev. B 95, 155201 (2017).
[2] D. Neubauer, PhD thesis, Stuttgart University (2017).
[3] A. Löhle, E. Rose, S. Singh, R. Beyer, E. Tafra, T. Ivek, E. I. Zhilyaeva, R. N. Lyubovskaya and M. Dressel, J. Phys.: Condens. Matter 29, 055601 (2017).

Contact

This image shows Martin Dressel

Martin Dressel

Prof. Dr. rer. nat.

Head of Institute

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