Mnzn ferrite core and its production method

Abstract

A method for producing a MnZn ferrite core used at a frequency of 1 MHz or more and an exciting magnetic flux density of 75 mT or less, the MnZn ferrite comprising 53-56% by mol of Fe (calculated as FeO), and 3-9% by mol of Zn (calculated as ZnO), the balance being Mn (calculated as MnO), as main components, and 0.05-0.4 parts by mass of Co (calculated as CoO) as a sub-component, per 100 parts by mass in total of the main components (calculated as the oxides); comprising a step of molding a raw material powder for the MnZn ferrite to obtain a green body; a step of sintering the green body and cooling it to a temperature of lower than 150° C. to obtain a sintered body of MnZn ferrite; and a step of conducting a heat treatment comprising heating the sintered body of MnZn ferrite to a temperature meeting Condition 1 of 200° C. or higher, and Condition 2 of (Tc−90)° C. to (Tc+100)° C., wherein Tc is a Curie temperature (° C.) calculated from the percentages by mol of FeOand ZnO contained in the main components of the MnZn ferrite, keeping the sintered body at the above temperature for a predetermined period of time, and then cooling the sintered body from the keeping temperature at a speed of 50° C./hour or less.