Patent ID: 7193824

Claim:
A disk drive comprising: a magnetic head which has a reading head using a tunneling magnetoresistive effect element (TMR element) and a writing head for generating a recording magnetic field according to a recording electric current provided in a coil, and which executes a data reading operation or writing operation to a disk medium; a controller to control a circumferential temperature of the TMR element by controlling the electric current to be supplied to the coil of the writing head at the time of a testing process for calculating a temperature coefficient with respect to a resistance value of the TMR element; a measuring unit which measures the resistance value of the TMR element by providing an electric current to the TMR element; a unit which calculates the temperature coefficient with respect to the resistance value of the TMR element based on the resistance value of the circumferential temperature of the element; and a determining unit which determines a pin hole state of a tunnel barrier layer included in the TMR element based on the temperature coefficient.