Magnetic hysteresis properties of BaFe12−xInxO19 ceramic ferrites with c-axis oriented grains

Abstract

To study the effects of reduced magnetic anisotropy on hysteresis loops of hard magnets for possible use in self-biased microwave devices, a new family of magnetically oriented (c-axis) In-substituted Ba ferrite was prepared by conventional ceramic techniques. Earlier studies of BaFe12−x(In,Sc)xO19 series in single-crystal form have shown that magnetization 4πM and anisotropy field Hk decrease sharply with increasing x. Since hysteresis loops with optimum energy products require uniformly small grains (1 to 3 μm), sintering temperatures were carefully controlled over a range from 1180 to 1075 °C for 2 h, depending on In content. For nominal values of x ranging from 0 to 1.5, square hysteresis loops with Hc values decreasing from 3500 to 150 Oe were recorded with a high-field hysteresisgraph. The effective Hk values were measured and compared with single-crystal data to estimate the degree of grain alignment for each composition.

Ferrite Properties and Technology Issues for Improved Microwave Systems

“…This concept, however, is not useful in the standard microwave bands because H c < 4πM R when the anisotropy field H A is reduced by design to lower the gyromagnetic resonance frequency appropriate to the desired operating band [12]. The maximum 4πM R that sets the propagation properties is then reduced to a value no greater than H c .…”

Magnetic and microwave properties of basal-plane oriented BaFe11In1O19 ferrite thick films processed by screen printing

“…The substitution of Sc or In for Fe 3+ has shown to reduce the anisotropy field ͑H A ͒ of the hexaferrite. [6][7][8] The design of X-band circulators and phase shifters requires the low anisotropy compared with the pure barium ferrite, high remanent and saturation magnetization, high Nèel temperature, and low FMR linewidth. Also, the Sc or In doping will stabilize the valence state of Fe 3+ and avoid high loss tangents.…”

Microstructural and magnetic properties of BaO‐Fe 2 O 3 –B 2 O 3 ‐SiO 2 glass ceramic with ZrO 2 as nucleating agent

“…Barium hexaferrite (BaFe 12 O 14 ), BF, have attracted much attention as permanent magnets, perpendicular magnetic recording media, and microwave device materials [1][2][3]. The wide applications of this compound originate from its relatively large magnetocrystalline anisotropy and good chemical stability.…”