Measurement of Dielectric and Magnetic Properties of Ferromagnetic Materials at Microwave Frequencies

T h e dielectric a n d m a g n e t i c properties of semi-conducting ferromagnetic materials such as ferrites have been t h e subject of intense s t u d y in recent years. Analytical expressions for t h e c o m p o n e n t s N a n d K of the permeability tensor of a loss-free single-crystal ferrite were derived by Polder. 1 These expressions were later modified to include a loss f a c t o r a . 2 , 3 Yager a n d others 4 measured t h e resonance absorption of single crystals of nickel ferrite a n d found very good agreement with t h e o r y provided t h e loss factor a was determined f r o m the w i d t h of t h e measured resonance absorption line. However, when A r t m a n a n d T a n n e n wald 6 measured t h e real a n d imaginary p a r t s of ju a n d k for polycrystalline ferrites t h e y found t h a t agreement with t h e o r y was s o m e w h a t less t h a n perfect if a was also determined from the measured line w i d t h . Discrepancies were observed for both real a n d imaginary p a r t s of n + 427