Hi chalnikkal, yes you can use those round mags. As someone else said: they are not very powerful and mostly good for toying around. I am also using them now to make a vertical turbine called my `Green Dream II', since the whole turbine is `saved' from the scrapyard: the mags from old microwaves; for the rotor I use 8 x 20 liter oil cans cut in half and stacked 90 degrees (alternating) on a single shaft to make a cute (but not very efficient) savonius rotor; the hub is a water pump from a vehicle; the two steel plates for the alternator are two square 3,2 mm pieces (they need not be round, only balanced); the enamel wire is .8 mm leftovers from previous jobs and the rest is tubing and pipes for the frame and stand. This is just a toy to show people that we are blessed with WIND AND WIND IS POWER TO BE HARNESSED. FOR FREE.
I use ferrites, 75 x 50 x 25 (24 per alternator) on the serious jobs, and having imported many of them, I have to spare should you be interested. They work well.
You can also go to Hugh Piggott's blog where he shows Pedro (from Portugal, where else) building an alternator with microwave mags, stacking them up in 3's to get more power. But honestly, they are just for fun and not worth trying to generate serious power. And as that man Hugh always says: HAVE FUN!!