Abstract: A method of testing anti-high temperature performance of a magnetic head comprises applying a second magnetic field with different intensities in a second direction and the changing first magnetic fields in a first direction, and measuring a plurality of second output parameter curves; and judging whether a variation that is beyond an allowable value is presented on the second output parameter curves, thereby screening out a defective magnetic head, therein the first direction is perpendicular to the air bearing surface of the magnetic head, and the second direction is perpendicular to the shielding layers of the magnetic head. The present invention can screen out defective magnetic heads that possess poor anti-high temperature performance without heating the magnetic head and with high precision.

Abstract: A method for measuring longitudinal bias magnetic field in a tunnel magnetoresistive sensor of a magnetic head, the method includes the steps of: applying an external longitudinal time-changing magnetic field onto the tunnel magnetoresistive sensor; determining a shield saturation value of the tunnel magnetoresistive sensor under the application of the external longitudinal time-changing magnetic field; applying an external transverse time-changing magnetic field and an external longitudinal DC magnetic field onto the tunnel magnetoresistive sensor; determining a plurality of different output amplitudes under the application of the external transverse time-changing magnetic field and the application of different field strength values of the external longitudinal DC magnetic field; plotting a graph according to the different output amplitudes and the different field strength values; and determining the strength of the longitudinal bias magnetic field according to the graph and the shield saturation value.

Abstract: A method for measuring the temperature rise induced by bias current/bias voltage in a magnetic tunnel junction, the method includes the steps of: (a) applying an external time-changing magnetic field to the magnetic tunnel junction; (b) measuring different first outer pin flip field values under different temperature values; (c) calculating the correlation between the temperature and the outer pin flip field according to the temperature values and the first outer pin flip field values; (d) measuring different second outer pin flip field values under different bias current/bias voltage values; (e) calculating the correlation between the bias current/bias voltage and the outer pin flip field according to the bias current/bias voltage values and the second outer pin flip field values; (f) calculating the correlation between the temperature and the bias current/bias voltage according to the results produced by the steps (c) and (e).

Abstract: A MR sensor comprises a first shielding layer, a second shielding layer, a MR element and a pair of hard magnet layers sandwiched therebetween, and a non-magnetic insulating layer formed at a side of the MR element far from an air bearing surface of a slider. The MR sensor further comprises a first non-magnetic conducting layer formed between the first shielding layer and the MR element, and the first non-magnetic conducting layer is embedded in the first shielding layer and kept separate from the ABS. The MR sensor of the invention can obtain a narrower read gap to increase the resolution power and improve the reading performance, and obtain a strong longitudinal bias field to stabilize the MR sensor so as to increase the total sensor area and, in turn, get an improved reliability and performance. The present invention also discloses a magnetic head, a HGA and a disk drive unit.

Abstract: A MR sensor includes a first shielding layer, a second shielding layer, a MR element formed therebetween, and a pair of hard magnet layers respectively placed on two sides of the MR element. The MR element comprises an AFM layer formed on the first shielding layer, a pinned layer formed on the AFM layer and a free layer formed between the pinned layer and the second shielding layer. The free layer is funnel-shaped, which having a first edge facing the air bearing surface and a second edge opposite the first edge, and the first edge has a narrower width than that of the second edge. The structure of the MR sensor can improve MR height control performance, and improve the ESD performance and decrease the PCN and RTN and, in turn, get a more stable performance. The present invention also discloses a magnetic head, a HGA and a disk drive unit.