The random M hexa-ferrite fibres had Ms values
slightly below single crystal values, as seen in most
polycrystalline samples, high coercivities implying
a small grain size, and were isotropic, shown by
their Mr/Ms values. Therefore any variation in
observed magnetic properties with change in
orientation of the fibre must be due to fibre
alignment effects, and not from alignment of
domains within the fibres. It was also demonstrated
with nickel calibration samples that shape
demagnetisation effects for the square-shaped
samples were negligibleBoth BaM and SrM random fibres had similar
Ms values of approximately 63 emu g1 after
1000 1C/3 h, with high coercivities for polycrystalline
samples of 428.1 and 452.8 kAm1, respectively.
It has been predicted that aligned ferrite
fibres will demonstrate an enhanced magnetisation
along the axis of alignment respective to perpendicular
to the axis, and this has been proven here
for the first time. Fibres aligned parallel to the
applied filed had Ms values equal to those of the
random fibres (within weighing errors), whilst
fibres aligned perpendicular to the field had Ms
values 62% and 75% lower, for BaM and SrM
respectively. M ferrite fibres aligned 451 and
parallel to H were equal. The fact that M fibres
exhibited this alignment enhancement with their
alignment not only parallel to, but also at 451 to,
H means in effect it covers a cone of 901 in which
this phenomenon can be applied