Mechanical Rotator: A Solution for Measurements Requiring High Magnetic Fields

Bulk materials are typically characterized using electrical resistivity measurements as a function of pressure doping, temperature, and applied field. However, as the dimensionality of the sample reduces, the magnetic field’s orientation to the sample becomes more crucial.

The alignment of the field to the sample in extremely anisotropic materials enables the analysis of exotic phases of matter including electron gases in topological insulators and semiconductors.

As the dimensions further reduce, magnetic fields can be used to manipulate electron transport, exposing new physics such as quantized transport and Majorana fermions.

The Challenges

  • Without any access to the sample, how could one alter the orientation of the field to the sample?
  • How can electrical contact be maintained with the sample?
  • How could a large magnetic field be rotated relative to the sample?
  • How can the Fermi surface of a sample be probed?
  • How can corrections be done for any misalignment of a sample to the magnetic field?

Oxford Instruments has the Solution

Mechanical Rotator

For measurements necessitating high magnetic fields, a mechanical motor can be employed to rotate the sample within the magnetic field. With a rotating sample, flexible electrical connections are possible.

  • Incorporating the mechanical drive rod with a stepper motor at room temperature, allows the sample angle to be fixed accurately
  • Permits access to larger magnetic fields than a vector magnet

Piezoelectic Rotator

For measurements where a high magnetic field is necessary, but where it is not possible to fit a drive rod, a piezoelectric rotator can be employed. In this configuration, the rotator is driven electrically and an encoder can be used to establish the sample’s angle.

  • Electrically driven
  • Allows access to larger magnetic fields than a vector magnet
  • Can be set up on systems where a mechanical drive rod will not be suitable
  • Simplified design without the need for a mechanical linkage between sample and room temperature
  • When integrated with a mechanical rotator, it allows rotation in numerous axes

Vector Magnet

A vector magnet, containing two or more orthogonal superconducting coils, allows the field orientation to be regulated by varying the current in each coil. This enables the field to be swept through complex paths in numerous axes.

Measurements necessitating higher frequency lines or optical access to the sample are feasible as the sample is fixed.

  • Sample is fixed - enables semi-rigid electrical connections to the sample
  • Mechanical drive rods are not needed
  • Free-space optical access to the sample
  • Compatible with rapid sample exchange systems
  • Correct control of field vector through magnet power supply

Choose the Right Option

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

Advantages:
- Temperature range from 1.4 to 300 K
- ESD protection integrated into sample holder
Vector Magnet <9 T

Typical magnets:
6 T vertical (Z), 1 T horizontal (X and Y) axes
9 T vertical (Z), 1 T horizontal (X and Y) axes
2, 3 2.5⁰ tilt full field
1 T rotation sphere
Triton 500 with 6/1/1 Vector Magnet and 72 mm bottom-loading sample exchange system

Advantages:
- 10 mK base temperature
- Fast sample exchange
- 14 high frequency and 48 low frequency lines to sample
- Optical access possible

This information has been sourced, reviewed and adapted from materials provided by Oxford Instruments Nanoscience.

For more information on this source, please visit Oxford Instruments Nanoscience.

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