Ferrites that are used in transformer or electromagnetic cores contain nickel,
zinc or Manganese compounds. They have a low coercivity, and are called soft
ferrites. Because of their comparatively low losses at high frequencies, they
are extensively used in the cores of Switched-Mode Power Supply (SMPS) and RF
transformers and inductors.
In contrast, permanent ferrite magnets (or hard ferrites) have a high remanence
after magnetization, and are made with iron oxide and barium and strontium
oxides. In a magnetically saturated state they conduct magnetic flux very well
and have a high magnetic permeability. This enables these so-called ceramic
magnets to store stronger magnetic fields than iron.