Short range order development in Ni3Mn alloys

The magnetic order development in polycrystalline Ni
3
Mn alloys has been studied as a function of atomic ordering during anneal at 500°C for times up to 32 hours after an initial quench from 1000°C. The cluster moments appear to saturate at about 5 × 10
^-17
emu, with an exponential growth characterized by a time constant of about 5-10 hours. The clusters grow to about 40 Å radius, assuming an aligned moment of 1 μ
B
per atom within clusters. The cluster density increases abruptly to 2.0 × 10
¹⁹
cm
^-3
after the initial 5-minute anneal, levels off, and then decays to about 1.0 × 10
¹⁹
cm
^-3
. These data suggest that the clusters "pop in" during the initial stages of short range order development, and then grow in size to saturation.