Barkhausen jumps in the magnetic hysteresis loop of a single permalloy thin
film square dot of 20 x 20 mum in size and 80 nm thick have been observed,
for the first time, with a magneto-optical ellipsometer which is capable t
o record a complete loop in time of seconds and in a single sweep of applie
d field, About 6000 loops have been measured and separately recorded: each
loop is different from the others. The statistical properties of the Barkha
usen jumps are presented and discussed.