transformers

[mettula]

Hello;
I have a quest about transformrs. I wish to know 3 main materials which are used to  make the core of a normal (not centre tapped) transformers for 50Hz range to step down 230V into 24V. The transformer is 5VA.
Are these 3 materials that can be used ; silicon steel, nickel iron and cobalt iron? or I am in the worng track (as usual  :-[  :'( )

Thanks for your help and patience

[walid]

Hi
I make a google search "transformrs core materials "
i get many information, the followinf is an example:
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19650009347_1965009347.pdf
hope it benefeted you