I'm questioning my self how effective hall measurements on anti-ferromagnetic materials are. At the moment I try to achieve hall measurements on Nickel-Oxide and failed numerous times.
Is this due to the anti-ferromagnetism? As I understand right, the material itself orients spins plain wise that they counter each other. But does this prevent an external magnetic field from penetrating the thin film and interact with the mobile charge carriers?
The reported mobilities and carrier concentrations vary from 1E-3 to several 100 cm^2/Vs and 1E12 1/cm^3 to 1E18cm^3, respectively. Considering the d-orbitals to participate in transport, I would assume the mobility is around 1 cm^2/Vs or slightly larger, similar to amorphous-Si.
Any suggestions on improving Hall-measurements on NiO? At the moment, I use structured NiO crosses with sputtered Au-Contacts(attached) on SiO2-Si Substrates. I will check on Ni-Contacts too. I'm using a LakeShore M91 Tabletop Hall-Setup with High Resistance option (1GOhm). Could anyone clarify on this topic or provide some tips on the measurements?
Do not use crosses of the semiconductor material to measure the Hall voltage, use a sheet of thin film 1-2 microns thick, 1 cm x 5 mm (or 1.5 cm x 1 cm) with Au contacts on top of this thin film as you have for the crosses. The distance between the Hall contacts (5 mm) will be less than the distance between current contacts. The current in the probe should be about 1 mA and the magnetic field shoud be 0.5 - 1 T
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