Why silicon steel is preferred for magnetic core materials of electrical machines to reduce hysteresis losses ?

Explanatory answer :

by steinmetz formula, 
                              Hysteresis loss,    Wh=n(Bmax)1.6f v watts

Where
n= hysteresis co-efficient
f= frequency of reversal of magnetism
v= volumeof magnetic material

from the above above relation, we conclude that  hysteresis loss (Wh) is proportional to hysteresis co-efficient (n) hence by selecting a magnetic material with low hysteresis co-efficient value and high electrical resistivity , the hysteresis loss can be reduced.

Hysteresis co-efficient value for different magnetic materials :

 n= 502 J/m³   for good dynamic sheet steel

 n= 191 J/m³    for silicon steel

 n= 7040 J/ m³   for hard steel

 n= 750-3000 J/ m³   for  for cast steel

 n= 2700-4000 J/ m³   for  cast iron

           out of these listed hysteresis co-efficient value for different magnetic materials, silicon steel has low hysteresis co-efficient value hence silicon steel is mostly preferred for magnetic core material to reduce hysteresis losses.