A magnetic head includes a coil, a main pole, a write shield, a lower return path section, and an accommodation section. The accommodation section accommodates at least part of the return path section. A first portion of the accommodation section has a first inclined surface. A second portion of the accommodation section has a second inclined surface. A coil element of the coil has a third inclined surface opposed to the first inclined surface, and a fourth inclined surface opposed to the second inclined surface. The lower return path section includes a first inclined portion extending along the first inclined surface, and a second inclined portion extending along the second inclined surface.

A magnetic head includes a coil, a main pole, a write shield, a lower return path section, and an accommodation section. The accommodation section accommodates at least part of the return path section. A first portion of the accommodation section has a first inclined surface. A second portion of the accommodation section has a second inclined surface. A coil element of the coil has a third inclined surface opposed to the first inclined surface, and a fourth inclined surface opposed to the second inclined surface. The lower return path section includes a first inclined portion extending along the first inclined surface, and a second inclined portion extending along the second inclined surface.

A card reader includes a writing coil that is provided to a magnetic head for recording magnetic data in a magnetic card, and a drive circuit that supplies a write current to the writing coil. The drive circuit is a chopping circuit that supplies a chopping current, on/off of which is switched in a specified cycle, as the write current to the writing coil. An on/off cycle of the chopping current is a cycle in which a length of a magnetized pattern in a recording direction is shorter than a reading gap formed in a core around which the writing coil is wound or a core around which a reading coil being separately provided from the writing coil is wound, the magnetized pattern in the recording direction being formed in the magnetic card by the chopping current in a period including one each of the on and the off.

A card reader includes a writing coil that is provided to a magnetic head for recording magnetic data in a magnetic card, and a drive circuit that supplies a write current to the writing coil. The drive circuit is a chopping circuit that supplies a chopping current, on/off of which is switched in a specified cycle, as the write current to the writing coil. An on/off cycle of the chopping current is a cycle in which a length of a magnetized pattern in a recording direction is shorter than a reading gap formed in a core around which the writing coil is wound or a core around which a reading coil being separately provided from the writing coil is wound, the magnetized pattern in the recording direction being formed in the magnetic card by the chopping current in a period including one each of the on and the off.

An apparatus, in accordance with one approach, includes a module having a first array of read transducers. A first electrical shielding layer is positioned above the first array of read transducers. An array of write transducers is positioned above the first electrical shielding layer. A second electrical shielding layer is positioned above the array of write transducers. A second array of read transducers is positioned above the second electrical shielding layer.

An apparatus, in accordance with one approach, includes a module having a first array of read transducers. A first electrical shielding layer is positioned above the first array of read transducers. An array of write transducers is positioned above the first electrical shielding layer. A second electrical shielding layer is positioned above the array of write transducers. A second array of read transducers is positioned above the second electrical shielding layer.

Dual and triple PMR writers are disclosed wherein the number of writer pads required to energize the selected PMR writer is minimized to three or four, respectively, with a coil configuration wherein separate top coils are connected by separate interconnects or side taps to separate bottom coils. Either top coils or bottom coils may be linked to a common W pad. Alternatively, there may be one bottom coil that allows all output current to flow to a common W pad. Coils may have a pancake or helical shape. In dual PMR writer embodiments, there may be one or two dynamic fly height heater coils. Magnetic performance in the selected writer of a dual PMR writer is similar to that of a single PMR writer with regard to erase width in AC mode (EWAC), Hy field, trailing and side shield return fields, down-track and cross-track gradient.

Dual and triple PMR writers are disclosed wherein the number of writer pads required to energize the selected PMR writer is minimized to three or four, respectively, with a coil configuration wherein separate top coils are connected by separate interconnects or side taps to separate bottom coils. Either top coils or bottom coils may be linked to a common W pad. Alternatively, there may be one bottom coil that allows all output current to flow to a common W pad. Coils may have a pancake or helical shape. In dual PMR writer embodiments, there may be one or two dynamic fly height heater coils. Magnetic performance in the selected writer of a dual PMR writer is similar to that of a single PMR writer with regard to erase width in AC mode (EWAC), Hy field, trailing and side shield return fields, down-track and cross-track gradient.

According to one embodiment, a magnetic disk device applies a bias voltage for measurement to a high frequency assist element according to a setting instruction of the bias voltage to measure a conduction current by in a recording head, calculates the resistance value in the supply path of the bias voltage from a relationship between the measured current and the bias voltage for measurement, and changes the bias voltage applied at the time of data recording based on the calculated resistance value.

According to one embodiment, a magnetic disk device applies a bias voltage for measurement to a high frequency assist element according to a setting instruction of the bias voltage to measure a conduction current by in a recording head, calculates the resistance value in the supply path of the bias voltage from a relationship between the measured current and the bias voltage for measurement, and changes the bias voltage applied at the time of data recording based on the calculated resistance value.