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Transport Measurements

All of the following systems are designed to measure the electrical properties of our samples. Measurements include I-V curves, resistivity, magnetoresistance, Hall effect and dynamic conductance. Typically we measure tens of mA to pA level and from tens of V to tens of nV.

Adiabatic Demagnetisation Refrigerator

Cryostat system that utilises the changes in entropy generated when a magnetic field is applied to a paramagnetic salt. The salt is placed in a low entropy state by the applied magnetic field. As the field is removed, the salt becomes more disordered, in the process removing entropy from the sample and thus cooling it. By varying the current in the superconducting magnet used to generate the field, one can achieve low temperatures stable to mK levels.

Temperature: 40 mK to 300 K
Magnetic Field: -6 T to 6 T

Helium Flow Cryostats

Two low temperature measurement systems. The sample is cooled by a flow of liquid helium, which is introduced to the evacuated sample chamber. The temperature is controlled by varying the helium flow rate, and using heaters situated near the sample.

An optional helium-3 insert allows measurements at 300mK.

Temperature: 300 mK to 300 K
Magnetic field: -9 T to 9 T.

Helium Dip Probe

System for simple transport measurements at liquid helium temperature . This system works essentially like a vacuum flask, with liquid helium in the central chamber. The sample is lowered into the helium using a sliding seal mechanism. Higher temperatures can be achieved by gradually lifting the sample away from the helium bath, but the stability is poor.

Temperature: 4.2 K to 300 K
Magnetic field: -5 T to 5 T

Magnetoresistance (MR) Rigs

The group possesses a variety of magnets for MR measurements. These include a probe station for contacting smaller complex samples, a furnace allowing measurements up to 650K and three dimensional control over the field/sample orientation.

Temperature: 300 K to 650 K
Magnetic Field: -6 T to 6 T

GHz Pulsed Measurement System

A magnetoresistance pulsed measurement system with a 1 GHz bandwidth. Primarily used for spin torque and domain wall motion experiments.

Temperatre: Room Only
Magnetic Field: 1 T to - 1 T

Point Contact Andreev Reflection

A system designed to measure the dynamic conductance of a point contact.  A three-dimensional piezoelectric motor allows lateral movement of the tip across the sample, and is used to form the point contact. Superconducting point contacts are used to measure the spin polarisation of a current flowing in a ferromagnet.

Temperature 4.2K
Magnetic Field: -5 T to 5 T