I recently came across an inductive charger that uses permanent
magnets as cores for the coils. What benefit does using a permanent
magnet have. Could someone direct me to some information on this
subject.
You may be mistaken. It is more likely that a small section of a core
is pre-biased, as the materials used for PM tend to be poor candidates
for efficient HF AC flux imposition.
Some polymer composite material and is used in LF motorc - which is
where magnetized material finds more frequent use.
Hitachi used to sell pre-biased E-core magnetics under the 'Hicoil',
'Hicoil-L' and 'Hiformer' trade marks, for applications below 100W and
40KHz. An EDN article from July 19, '78. It's not the kind of product
feature that would be easily recognized.
If your device is a non-contact inductively coupled charger, which the
term 'inductive charger' suggests, the presence of permanent magnets
may have nothing to do with efficient power conversion, and more to do
with maintaining coupler surface contact and orientation in the
charging station.
RL