Temperature dependence of the hysteresis properties of polycrystalline spinel ferrite and garnet materials

The hysteresis properties of polycrystalline spinel ferrite and garnet compositions with in the 380 to 5000 gauss range were investigated to determine their temperature stability over the range from -55 to +85°C. Magnesium, nickel, and garnet type compositions, which possess low microwave dielectric losses ( ) were chosen for investigation. Many of the materials exhibited suitable room temperature characteristics for microwave latching applications. The remanent magnetic flux density, coercive force, and squareness of the hysteresis loop for these compositions were found to be quite temperature dependent, thus placing a limitation on their usefulness. Lithium ferrites, which normally possess high Curie temperatures and high microwave dielectric losses were also investigated. It was found that in these materials the dielectric losses can be reduced to while providing superior temperature stable hysteresis characteristics. The merits of the lithium ferrites indicate promise for microwave latching applications requiring temperature stability.