Temperature dependence of Ba-ferrite bubble memory bias magnets as a function of magnet geometry

The coefficient of the linear variation of field strength with temperature in Ba-ferrite is shown to have a simple functional dependence upon the permeance coefficient (B/H ratio) of the magnet structure. Using cylindrical magnets with aspect ratios of 0.030 to 4.00 and measuring the field strength from -35 °C to +65 °C, we observe temperature coefficients varying by about 40% from -0.150%/°C to -0.207%/°C These values have a simple relationship to calculated magnet permeance coefficients. An analog circuit approach is presented for calculating the permeance coefficients of complex bias magnet systems. The temperature coefficients predicted from the calculated permeance coefficients and the measured bias field temperature dependences are in good agreement.