Net spin

Cation $($Bohr magnetons$)$

Fe$3+5$

Fe$2+4$

Ni$2+2$

Table $1$: Magnetic moments for Fe and Ni ions.

Nickel ferrite $($NiFe$2$O$4)8$ is a cubic ferrite with the inverse spinel structure. The

unit$-$cell edge length of $0\mathrm{.}8337$ nm$.$ Using the data provided for net spin magnetic

moments for the ferrous and nickel ions in Table $1,$ estimate

$($a$)$ The saturation magnetization $(10$ Marks$)$

$($b$)$ The saturation flux density $(5$ Marks$)$

$($Note: $$B $=9\mathrm{.}27\backslash$times $1024$ A m$2$ and $0=4\backslash$pi $\backslash$times $107$H$/$m$).$