Magnetic and electric properties of Ni ferrite with Gd substitution

S. E. JACOBO; P. G. BERCOFF

Buenos Aires

Congreso; 9° Congreso Internacional de Metalurgia y Materiales SAM-CONAMET 2009; 2009

The effect of Gd-for-Fe substitution on the structure, magnetic and dielectric properties of Ni-ferrite are investigated. Five samples with nominal composition NiFe2.00-yGdyO4, y=0.00; 0.04; 0.10, 0.12 and 0.15 were prepared by the auto-combustion method. For y > 0.04, a mixture of a substituted ferrite and variable quantities of GdFeO3 were obtained. Gadolinium solubility increases when the temperature of the thermal treatment is higher. Saturation magnetization Ms slowly decreases with Gd content up to y= 0.10 and abruptly decreases for higher y values. The same behavior is observed for two different thermal treatments. The formation of a gadolinium ferrate orthorhombic phase and the particle size reduction leads to an abrupt increase in Hc. Electromagnetic measurements show that Gd2O3 tends to increase the cut-off frequency and magnetic loss tangent (tan δ(µ´) ) in the range of 250MHz to 1000MHz. For y < 0.10, an increase in the initial permeability (µ´) is observed. Gd3+ ions tend to flatten the ε´ vs.  frequency curves from 20MHz on.  Although the sample with y=0 has the lowest resistivity, its ε´ is not the highest, indicating that there exists another mechanism with more effective influence on ε´.