Magnetic Characterisation

We have a range of analytical instruments for characterising the magnetic behaviour of materials. These include systems dedicated to measurement of single structures to those suitable for thin films and bulk samples.

Optical Techniques

Focussed MOKE Magnetometry

This has been developed by Dr Dan Allwood for investigation of patterned magnetic elements. The system uses a 2.2 W continuous wave laser (Coherent Verdi) operating at a wavelength of 532 nm and is sensitive to single magnetisation transitions in individual nanostructurse. It is equiped with a range of detectors, from standard Si photodiodes to avalanche photodiodes and photomultiplier tubes for GHz bandwidth measurements. We are also able to generate 5 ns - 10 µs pulsed magnetic fields during MOKE measurement of samples using commercial current pulsers.

Radial MOKE Magnetometry

High-Field MOKE Magnetometry

Measurements on magnetic thin films under fields up to 0.5 T.

Low-Field MOKE Magnetometry

Suitable for analysis of soft magnetic thin films. This is housed in a shielded room to create a low noise environment.

Photoluminescence Magnetometry

Non-optical Techniques

Magnetoresistance Magnetometry

Suitable for the analysis of both magnetic thin films and devices in fields of up to 0.5 T.

Induction Magnetometry

Vector Network Analyser (VNA) Ferromagnetic Resonance Magnetometry (FMR)

Vector Network Analyzer – Ferromagnetic Resonance Magnetometry is a non-destructive measurement technique that probes the dynamic behaviour of a magnetic material in the frequency range of MHz to GHz.

The ferromagnetic resonance response that is probed is a collective excitation of the magnetic moments causing the precession around an applied field direction. This precession is in phase across all the moments within a sample, and can be driven by the application of both a magnetic field and a radio-frequency signal. Due to the collective nature of this response, material characteristics can be determined.

The VNA-FMR set-up within our lab allows for multiple measurement types that can be used, Field-Domain (both reflection and transmission), Frequency-Domain (reflection and transmission), and Field Modulated-Domain.  

The key characteristics that can be investigated are:

Imaging Techniques

Magnetic Force Microscopy (MFM) (Veeco Dimension 3100)

This is used to perform atomic and magnetic force microscopy (AFM/MFM). A silicon pyramidal tip, coated with magnetic material, is vibrated close (~50 nm) to the surface of a sample and rastered in order to scan an area up to 500 µm x 500 µm. The phase, frequency or amplitude shift generated by the interaction of the tip with the sample surface provides information about the sample. In AFM, this is topological information. In MFM, with a magnetically-coated tip, the image is related to the sample's magnetic domain structure.

Magneto-optical Faraday Imaging

  • Saturation Magnetisation
  • Magnetocrystalline Anisotropy
  • Gilbert Damping.