| Real and imaginary parts p. and p. of the initial permeability
p.0 were determined on toroidal samples of Ni-Zn ferrite
of nominal composition Ni0•3Zn0•7Fe20 4 using type 260-AP
Boonton Q-meter in the frequency range 100 Kc/s to 10
Mc(s. Both fLo and the quality factor Q varied with the
microstructure which had been well characterised in part I
of this report. The product p.0Q had a maximum of 23,720
at 100 Kc/s and 2885 at 1.5 Kc/s and p.0 had maximum
values of 1250 and 1572 respectively at the above frequencies
for a material sintered at 1200°C for 100 hours. The
Snoek relationship correlating p.0 and fr, the peak frequency
of p. giving fr(fL0·1)=constant was used to relate variation
of fLo with fr. The grain size also influenced the value
of p.0 and the Kersten relationship p.0 = const. x D, where
D is distance between domain pinning inclusions, was used
to relate grain size and permeability. Sintered pellets of different
stoichiometric deviations and processed by different
grinding media were used for d.c. resistivity measurement.
The resistivity showed a maximum value of 107 ohms-em
for a 1.5 mole% Fe20 3 deficient sample ground with alumina
and a minimum of 1.3 x 102 ohm-em for the material
ground with steel. |
