A Discussion on the Errors for the in Situ Magnetic Measurements in Hydrostatic High Pressure Vessel (2)－The Influence of Demagnetic Field

To study the influence of demagnetic field in the hydrostatic high pressure vessel, we selected 6 samples with different slice-number (n=1, 3, 5, 7, 10, 13) of amorphous alloy Fe46.3Co0.03Ni46.5Si3.75V0.92B2.5 ribbon, inserted them into multiple electric solenoid and measured the magnetization, magnetic permeability and initial magnetization, respectively, at 400 Hz. We found that: (1) The more the slices of sample, the stronger the influence of demagnetic field was, which leaded in surprising errors of m and i. For the sample with 1 slice, we obtained the optimal values, m=4 430, i=3 396. (2) With the increase of slice number (n=1~13), we measured saturation magnetic induction Bs=0.837～0.762T, indicating the influence of demagnetic field on Bs was much small. (3) To reduce the error from demagnetic field, thinner sample could be used, for example thin film with 0.2 m thick. (4) To eliminate the error from demagnetic field, closed magnetic circuit must be adopted, such as ring rolled up by amorphous alloy ribbon.