Core-shell structured Mn-Zn-Fe ferrite/Fe-Si-Cr particles for magnetic composite cores with low loss

Abstract A Mn-Zn-Fe ferrite layer, several hundred nanometers thick, was deposited on the surface of Fe-3.5Si-4.5Cr (mass%) powder particles as an insulating material by an ultrasonic enhanced ferrite plating method. The compositions of the Mn-Zn-Fe ferrite layer were Mn 0.18 Zn 0.27 Fe 2.55 O 4 , Mn 0.38 Zn 0.25 Fe 2.37 O 4 , and Mn 0.54 Zn 0.24 Fe 2.22 O 4 . The core loss ( P cv ) performances of the compacted cores and magnetic properties of the core-shell structured powders were evaluated. All the ferrite-coated cores exhibited a saturation flux density ( B s ) in the range of 1.54–1.56 T derived from their soft magnetic metal and ferrite composition. All ferrite-coated cores annealed at 773 K exhibited a constant permeability µ′ in the frequency range up to 50 MHz owing to the insulating effect of the ferrite layer, and the Mn 0.54 Zn 0.24 Fe 2.22 O 4 ferrite-coated core exhibited the highest real permeability µ′ of 56 at 50 MHz. The core loss of the Mn-Zn-Fe ferrite-coated Fe-3.5Si-4.5Cr cores was 604–738 kW/m 3 at 100 kHz and 50 mT, which was much smaller than that obtained for the Fe-3.5Si-4.5Cr core without a ferrite layer (3617 kW/m 3 ). The eddy-current loss ( P e ) of the Mn-Zn-Fe ferrite-coated Fe-3.5Si-4.5Cr cores considerably decreased compared with those of the non-coated Fe-3.5Si-4.5Cr core owing to the insulating properties of the ferrite layer.