Mn–Zn ferrites for magnetic sensor in space applications

We describe the optimization of Mn–Zn ferrites having a high permeability between −50 and +150°C. These ferrites are intended to be integrated into a magnetic field sensor for space mission. The chemical composition Mnx2+Zny2+Fe0.052+Ti0.014+Fe23+O4 was investigated by varying the Mn∕Zn ratio. The magnetic characterizations revealed that the initial permeability was increased for high Zn content while the Curie temperature was decreased. A local maximum of the permeability was observed at a specific temperature meaning, the magnetocrystalline anisotropy K1 became zero. The temperature T0 at which K1 was canceled (compensation temperature) depends on the chemical composition just like the Curie temperature TC: the higher the zinc content, the lower T0 and TC. The best compromise was obtained for a ferrite formulation with a Mn∕Zn ratio around 1.8 and with a small titanium oxide addition. Permeability higher than 2400 was obtained between −50 and +150°C and up to 500kHz. The use of ferrite core with the bes...