Highly resistive Mn-Zn ferrite films prepared from aqueous solution for GHz conducted noise suppressors

We have prepared Mn-Zn ferrite films (MnxZnyFezO4.00-delta: 0.23 < x < 0.30, 0.0 < y < 0.38, 2.39 < Z < 2.64) that are highly permeable in GHz range. The film resistivity p increased as the amount of Fe content z decreased and very high surface resistance R > 10(8) Omega/sq was attained for the film having z < 2.6. The deposited Mn-Zn ferrite films had a large saturation magnetization M, =380-460 emu/cm(3) and relatively low coercivity H-c= 11-29 Oe. The Mn-Zn ferrite films contacted to a microstrip line (50 Omega) exhibited very large transmission loss Delta P-loss per thickness t, Delta P-loss/t, of about 10 times larger than that of commercialized composite sheet. They exhibited sufficiently low reflection coefficient S-11 < -10 dB. These films were applicable as noise current suppressors deposited on an interlayer of multilayer printed circuit boards. (c) 2005 American Institute of Physics.