Magnetic properties and grain growth stability of nanocomposite Fe–ZrO2 granular solids prepared by mechanical milling

Correlations between the grain size [or the diffracting particle size (DPS)] and the magnetic properties of mechanically milled Fe–ZrO2 nanocomposite powders are reported. Nanocomposite powders with iron volume fractions below, near, and above the percolation value were annealed at temperatures between 573 and 1083 K and investigated. The composite as‐milled powders exhibited enhanced coercivities (≳300 Oe) compared to similar mechanically milled iron powders. The iron diffracting particle size (grain size) as a function of annealing temperature showed two regimes. The first regime, corresponding to temperatures at and below 773 K, consisted of enhanced coercivities and remanence ratios with a relatively stable iron diffracting particle size of ∼25 nm. In the second temperature regime, above 773 K, the DPS increased, but remained well below the value for pure iron. Concomitant with this increase, large reductions in the coercivities were observed in the second regime.