micky wrote:
More about magnetism and MRI's

It came up here wrt my planned MRI that there seemed to be things not
made out of iron that were subject to magnets. By coincidence I came
across this.

From Wikip ... http://en.wikipedia.org/wiki/Ferrite_core

Ferrites
Ferrites are ceramic compounds of the transition metals with oxygen,
which are ferromagnetic but nonconductive. Ferrites that are used in
transformer or electromagnetic cores contain nickel, zinc, and/or
manganese compounds.

So I guess all these compounds and maybe more (that aren't used
commericialy or not in transformers) would be magnetic like iron, but
not containing iron, and to top it off, nonconductive.

What a complicated world we live in, where there are general rules and
exceptions to the rules.




Nowadays, people are most likely to see ferrite cores as the small
cylinders near the end of electric wires, such as USB cables, power
supply adapter cables, etc.


"hey have a low coercivity and are called "soft ferrites" to
distinguish them from "hard ferrites", which have a high coercivity
and are used to make ferrite magnets. The low coercivity means the
material's magnetization can easily reverse direction without
dissipating much energy (hysteresis losses), while the material's high
resistivity prevents eddy currents in the core, another source of
energy loss. The most common soft ferrites a

Manganese-zinc ferrite (MnZn, with the formula MnaZn(1-a)Fe2O4).
MnZn have higher permeability and saturation levels than NiZn.
Nickel-zinc ferrite (NiZn, with the formula NiaZn(1-a)Fe2O4). NiZn
ferrites exhibit higher resistivity than MnZn, and are therefore more
suitable for frequencies above 1 MHz.
"

Even iron transformer plates, are plates glued together to avoid
conduction.

Greg.