Magnetic susceptibility of tungsten carbide: Relaxation and impurity effects

The magnetic susceptibility χ of coarse-grained WC and nanocrystalline n-WC tungsten carbides has been studied in a temperature range of 300–1250 K. The dependence χ (T) for coarse-grained WC carbide has no singularities. A stable particle size of about 55 nm remains in the n-WC nanopowder after annealing at 300–1200 K, whereas the relaxation of microstrains occurs at 550–920 K. The dependence χ(T) for nanocrystalline n-WC carbide in a range of 550–920 K exhibits features associated with the annealing of microstrains, which reduces the contribution of orbital paramagnetism to the susceptibility of n-WC carbide and initiates the precipitation of small iron and cobalt impurities in the form of superparamagnetic particles.