Synthesis and structural, magnetic and magnetotransport properties of permalloy powders containing nanoparticles prepared by arc discharge

• New method of arc discharge used to synthesise permalloy containing nanoparticles.
• The highest quality powders were made using a 78% Ni permalloy rod in N2.
• The Saturation moment was slightly less and the coercive field was low (3 mT).
• MR contributions from the spin-dependent tunneling between the particles.

We report the synthesis of permalloy powders that were made using an arc-discharge method and with 78% or 45% Ni concentrations in N2 or Ar. Our research was motivated by the fact that magnetic nanoparticles displaying large magnetoresistances are useful for magnetic field sensors applications. The permalloy powders contained some nanoparticles and the particle sizes ranged from 10 nm to ∼20 μm. The highest quality powders were made using a 78% Ni permalloy rod in N2 where the coercivity was low (0.3 mT) and the saturation moment per formula unit was slightly less than that expected for the bulk compound. Magnetoresistance was observed in a cold pressed pellet where it is likely to be dominated by the ordinary magnetoresistance and spin-dependent tunneling between the particles.