An in-situ technique for the acoustic emission monitoring of burnish heads while they are cleaning or burnishing magnetic media is described. Those leads exposed within the bottom surface of the package body are created through the utilization of a standard leadframe with additional lead features that are electrically isolated subsequent to a molding process through the use of a partial saw method. Furthermore, the stress occurring from the encapsulation resin is absorbed by the self flexural deformation of the die pad and the lead, which are thinned, thereby improving the connection reliability. The magnetic core precursor is produced mixing the glassy alloy powder with the insulating material, compacting the mixture to form a magnetic core precursor, and annealing the magnetic core precursor at a temperature in the range between K and Tg K to relieve the internal stress of the magnetic core precursor. Further, the particular configuration and manner of operation of Q1 and Q2 enable reduction of the gate capacitance switching loss when operating under low load current conditions. In one embodiment, a recording magnetic head includes coil conductors and magnetic pole pieces putting the same therebetween, in which a main magnetic pole piece is formed into a planar structure and a magnetic film connected with the main magnetic pole piece in a magnetic coupling relation is curved in the direction of the film thickness.