Laboratory for transport
properties measurements (Hall effect setup)
is equipped with a conventional electromagnet (magnetic field up
to 1.5 T), a Hall effect setup and an ARS Displex DE202N
closedcyclehelium cryostat (for low temperature measurements between 7
and 300 K).
The transport
properties measurements (Hall effect experiment) consists of:

The Electromagnet
(hand made). This electromagnet can realize a magnetic field of up
to 1.5 T for pole distance of 1 cm. In case of low temperature
measurements, the pole distance is 7 cm and the maximum value ofthe
magntic field is 0.5 T.

The Power
supply for electromagnet is Delta electronika
series 3000, model SMD: 120 V
 25
A.

The Keithley 220
Programmable Current Source: (DC current
range: 2 nA – 100 mA).

The Keithley 705
Scanner with Keithley 7065 Hall Effect Card, which is
designed to assist in making resistivity and Hall voltage
measurements on several types of semiconductor speciments.

The Keithley 196
System DMM is a five function autoranging digital multimeter.
The DC voltage measurements from 100 nV to 300 V. Resistance
measurements from 100 mW to 300 M W. AC voltage measurements from 1
mV to 300 V. DC current measurement from 1 nA to 3 A., and AC
current measurements from 1 nA to 3A.

The Close cycle
helium gas cryostat (ARS, model Displex DE202N) for temperature
measurements between 6 and 300 K.

The Lake Shore
DRC91CA Temperature Controller.

A Pfeiffer Vacuum
pump for air evacuation from cryostat.

A PC computer
for experiment running and data collecting.
Measurements:
Using the Halleffect set
up it is possible to measure:
1. Specific electrical resistivity using the Van der Pauw method.
2. The Hall voltage, i.e. the Hall constant. Combying this and the
electrical resistivity data it is possible to determine carriers type,
concentration and mobility.
Specific electrical resistivity measurements are done using the
Van der Pauw method. At first, it is necessary to create 4 electrical
contacts on the sample. The electrical resistivity is measured by
applying the current between two adjacent terminals and reading the
voltage at the other two terminals. The total of 8 measurements is made
for all possible combinations of measurements among the 4 contacts. A
specific electrical resistivity is calculated according to the Ohms law
using values of applied currents and measured voltages, taking into
account the proportionality coefficients based on the shape of the
sample.

Electrical resistivity of YBa_{2}Cu_{3}O_{7}
superconducting oxide. 
