The invention generally relates to hard disk drives with a disk and a read/write head, and methods for preventing contact between the disk and the read/write head. The hard disk drive includes a z-axis actuator configured to control movement of the read/write head, and to prevent contact between the read/write head and the disk, based on signals from a controller that indicate when the distance between the read/write head and the disk are outside a predetermined range, such as between 0 and 10.0 nm.

According to one embodiment, a magnetic disk drive selects in command evaluation in reordering processing, a command accessible in a shortest time. The device determines whether media bumps which influence a dynamic flying height (DFH) control exist in a seek section between completion of a previous command and start of a selected command or not, calculates a latency necessary for avoidance of the media bumps if it is determined by the determination that the media bumps which influence the DFH control exist, and selects the command accessible in the shortest time including the time obtained by summing the latency calculated by the calculation as the command to be next processed.

A data storage device is disclosed comprising a head actuated over a disk, wherein the head comprises a fly height actuator (FHA). An FHA control signal is applied to the FHA, wherein the FHA control signal comprises a rectangular wave having a duty cycle in the range of ten percent to thirty percent. While applying the FHA control signal to the FHA, the head touching down onto the disk is detected.

The invention generally relates to hard disk drives with a disk and a read/write head, and methods for preventing contact between the disk and the read/write head. The hard disk drive includes a z-axis actuator configured to control movement of the read/write head, and to prevent contact between the read/write head and the disk, based on signals from a controller that indicate when the distance between the read/write head and the disk are outside a predetermined range, such as between 0 and 10.0 nm.

The invention generally relates to a hard disk drive with a disk, a read/write head, a z-axis actuator, and a controller. A surface of the disk and/or the head can be bare and thus devoid of any overcoat or lubricant layer, or alternatively the disk surface can have one or more layers with a combined thickness of less than 4 nanometers and the head can have a layer with a thickness of less than 2 nanometers. The hard disk drive can be enclosed, and its enclosed space can be a low pressure environment such as a near-zero or a zero pressure environment.

A system for determining a fly height includes a first head of a disk drive, a second head of the disk drive, a capacitive sensor circuit coupled to the first head and the second head, and a logic device coupled to the capacitive sensor circuit. The capacitive sensor circuit is configured to measure a first capacitance between the first head and the first disk, remove noise from the first capacitance using a second capacitance between the second head and the second disk, and based thereon determine a corrected first capacitance. The logic device is configured to determine the fly height between the first head and the first disk using the corrected first capacitance.

A method for determining a fly height includes measuring a first differential voltage between a first head of a disk drive and a reference voltage with a first front end circuit, converting the first differential voltage to a first analog current signal with the first front end circuit, and converting the first analog current signal to a second differential voltage with a first back end circuit. The first front end circuit is coupled with the first head. The first back end circuit is coupled with the first front end circuit. The method further includes determining a first capacitance between the first head and a first disk of the disk drive based on the second differential voltage and determining the fly height between the first head and the first disk using the first capacitance.

The invention generally relates to a hard disk drive with a disk, a read/write head, a z-axis actuator, and a controller. A surface of the disk and/or the head can be bare and thus devoid of any overcoat or lubricant layer, or alternatively the disk surface can have one or more layers with a combined thickness of less than 4 nanometers and the head can have a layer with a thickness of less than 2 nanometers. The hard disk drive can be enclosed, and its enclosed space can be a low pressure environment such as a near-zero or a zero pressure environment.

A slider of a magnetic recording head has a leading edge, a trailing edge, and an air bearing surface between the leading and trailing edges. A sensor is situated at the trailing edge of the slider and configured to sense presence of a lube droplet or other contaminant at the trailing edge.

The invention generally relates to a system for achieving reduced head-media spacing (HMS) in a hard disk drive (HDD) by providing active control over the positioning of a read/write head relative to a rotating magnetic data recording and reading surface of a disk. The system is configured to monitor and adjust positioning of the read/write head in real, or near-real time during disk rotation to maintain the HMS between a magnetic transducer of the read/write head and the disk surface within a defined range, generally between 1.0 nm and 10.0 nm, and, in some embodiments, approximately 4.3 nm. The system replaces the conventional an air bearing surface (ABS) design with a fully active suspension to maintain the head flying height within the desired range. The system further allows for each of the magnetic transducer and disk surface to be to be devoid of any overcoat or lubricant layers.