Hi,

Diamagnetic materials are repelled by a magnetic field, just to clear you or more simply we can say 

if any atom have all paired electron in there orbit it can considered as Diamagnetic 

if any atom with some unpaired electrons are there it will be called as paramagnetic 

Paramagntic Means those which shows attratction towards magnetic field

Diamagnetic Means those which shows Repulsion towards magnetic field

For better understaing please watch our JEEpeJEET chemical bonding on MOT 

Thanks