Bulk materials are routinely characterised using electrical resistivity measurements as a function of temperature, pressure doping and applied field. However, as the dimensionality of the sample decreases, the orientation of the magnetic field to the sample becomes more important.
For highly anisotropic materials, the alignment of the field to the sample allows for the study of exotic phases of matter including electron gases in semiconductors and topological insulators.
As the dimensions further decrease, magnetic fields can be used to control electron transport, revealing new physics such as Majorana fermions and quantised transport.
For measurements requiring high magnetic fields, a mechanical motor can be used to rotate the sample within the magnetic field. Flexible electrical connections are possible with a rotating sample.
For measurements where a high magnetic field is required, but where it is not possible to install a drive rod a piezoelectric rotator can be used. In this configuration the rotator is driven electrically and an encoder can be used to determine the angle of the sample
A vector magnet, comprising 2 or more orthogonal superconducting coils allows the field orientation to be controlled by varying the current in each coil. This allows for the field to be swept through complex paths in multiple axes.
With the sample that is fixed, measurements requiring higher frequency lines or optical access to the sample are possible.
|Magnetic field||Number of rotation axes||Typical performance||Typical configuration|
|Mechanical/Piezo Rotator||<16 T||1 (or 2 if Mechanical and Piezoelectric Rotator are combined)||±180 ° rotation (limited by sample wiring)||
14 T TeslatronPT with mechanical rotator measurement probe
|2, 3|| 2.5 ⁰ tilt full field
1 T rotation sphere
Triton 500 with 6/1/1 Vector Magnet and 72 mm bottom-loading sample exchange system