Heater AC Voltage Induced Flying Height Modulations

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Wei Hua ◽  
Kang Kee Ng ◽  
Shengkai Yu ◽  
Weidong Zhou ◽  
Kyaw Sett Myo
Keyword(s):  
Electrostatic Force ◽  
Laser Doppler Vibrometer ◽  
Drive Level ◽  
Flying Height ◽  
Air Bearing ◽  
Skew Angle ◽  
Frequency Method ◽  
Disk Interface ◽  
Height Control ◽  
Disk Contact

For a thermal flying-height control (TFC) slider, its heater is usually provided with DC voltage. However, recently, both DC and AC voltages may be supplied to the heater. Unlike supplying AC voltage to the slider and disk in the past, the AC voltage to the heater will not only produce a thermal protrusion on the slider, but also leaves a part of the AC voltage on the slider/disk interface. The voltage acts as the electrostatic force and can be used for further control of the slider, even in the drive level. Simulations show that the flying height modulation is highly related to the AC frequency. By sweeping the AC frequencies while monitoring the flying height and pitch angle modulations, the first and second pitch modes of air bearing frequencies can be experimentally obtained without slider/disk contact. The roll mode frequency is also obtainable when the skew angle is not zero. The simulation results agree well with the experimental results obtained by a laser Doppler vibrometer (LDV). Therefore, the sweeping AC frequency method provides a practical scheme to obtain the air bearing frequencies without any slider/disk contact, even in the drive level.

Effect of Slider Bias Voltage and Humidity on Wear and Contact Potential

2016 ◽  
Author(s):  
Karcher Morris ◽  
Liane Matthes ◽  
Frederick E. Spada ◽  
Andrey Ovcharenko ◽  
Bernhard E. Knigge ◽  
...  
Keyword(s):  
Bias Voltage ◽  
Electrostatic Force ◽  
Flying Height ◽  
Head Disk Interface ◽  
Kelvin Probe ◽  
Contact Potential ◽  
Disk Interface ◽  
Height Control ◽  
Before And After ◽  
Kelvin Probe Method

The effect of slider bias voltage and humidity on wear at the head/disk interface is investigated. Wear of thermal flying height control sliders is studied as a function of head/disk bias voltage, relative humidity, and heater power. The electrostatic force and the contact potential at the head/disk interface is monitored before and after head wear using the noncontact Kelvin probe method.

Effect of Head–Disk Interface Biasing and Relative Humidity on Wear of Thermal Flying Height Control Sliders

2017 ◽  
Vol 65 (2) ◽  
Author(s):  
Liane M. Matthes ◽  
Frederick E. Spada ◽  
Andrey Ovcharenko ◽  
Bernhard E. Knigge ◽  
Frank E. Talke
Keyword(s):  
Relative Humidity ◽  
Flying Height ◽  
Head Disk Interface ◽  
Disk Interface ◽  
Height Control ◽  
Thermal Flying Height Control

scholarly journals Parametric Investigations at the Head-Disk Interface of Thermal Fly-Height Control Sliders in Contact

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Sripathi V. Canchi ◽  
David B. Bogy ◽  
Run-Han Wang ◽  
Aravind N. Murthy
Keyword(s):  
Hard Disk Drives ◽  
Air Bearing ◽  
Head Disk Interface ◽  
Bearing Surface ◽  
Surface Design ◽  
Disk Interface ◽  
Height Control ◽  
Experimental Findings ◽  
And Control ◽  
Fly Height

Accurate touchdown power detection is a prerequisite for read-write head-to-disk spacing calibration and control in current hard disk drives, which use the thermal fly-height control slider technology. The slider air bearing surface and head gimbal assembly design have a significant influence on the touchdown behavior, and this paper reports experimental findings to help understand the touchdown process. The dominant modes/frequencies of excitation at touchdown can be significantly different leading to very different touchdown signatures. The pressure under the slider at touchdown and hence the thermal fly-height control efficiency as well as the propensity for lubricant pickup show correlation with touchdown behavior which may be used as metrics for designing sliders with good touchdown behavior. Experiments are devised to measure friction at the head-disk interface of a thermal fly-height control slider actuated into contact. Parametric investigations on the effect of disk roughness, disk lubricant parameters, and air bearing surface design on the friction at the head-disk interface and slider burnishing/wear are conducted and reported.

Air Bearing Pushback in Heat Assisted Magnetic Recording

2019 ◽  
Author(s):  
Shaomin Xiong ◽  
Robert Smith ◽  
Chanh Nguyen ◽  
Youfeng Zhang ◽  
Yeoungchin Yoon
Keyword(s):  
Magnetic Recording ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Disk Drive ◽  
Flying Height ◽  
Air Bearing ◽  
Magnetic Media ◽  
Heat Assisted Magnetic Recording ◽  
Height Control ◽  
Different Dimensions

Abstract The air bearing surface is critical to the spacing control in current hard disk drives (HDDs). Thermal protrusions, including thermal flying height control (TFC) and writer coil protrusion, drive the reader/writer elements closer to the magnetic media. The spacing control actuation efficiency depends on the air bearing push back response after the TFC or writer protrudes. In the next generation hard disk drive technology, heat assisted magnetic recording (HAMR), laser induced protrusions further complicate the spacing control. The laser induced protrusions, such as the localized NFT protrusion and a wider change of the crown and camber, have very different dimensions and transient characteristics than the traditional TFC and writer protrusion. The dimension of the NFT protrusion is relatively smaller, and the transient is much faster than the TFC protrusion. However, it is found that the NFT protrusion is large enough to generate an air bearing push back effect, which changes the read and write spacing when the laser is powered on. To accurately control spacing in HAMR, this push back effect has to be taken into account.

Design Optimization of the Taper-Flat Slider Positioned by a Rotary Actuator

1995 ◽  
Vol 117 (4) ◽  
pp. 588-593 ◽  
Author(s):  
Sang-Joon Yoon ◽  
Dong-Hoon Choi
Keyword(s):  
Optimization Technique ◽  
Leading Edge ◽  
Flying Height ◽  
Air Bearing ◽  
Skew Angle ◽  
Optimum Configuration ◽  
Rotary Actuator ◽  
Design Variables ◽  
Augmented Lagrange Multiplier ◽  
Typical Configuration

In this paper, an optimization technique is utilized to find an optimum configuration of the taper-flat slider positioned by a rotary actuator for enhanced static air-bearing characteristics. The aim of optimization consists in simultaneously minimizing the variation in flying height from a target value, maximizing the smallest pitch angle, and minimizing the largest roll angle, over the entire magnetic recording band. As the design variables, the leading edge taper angle and rail width of a taper-flat slider, and the skew angle at the inside track are chosen since they seem to be the most influential parameters on air-bearing characteristics. The optimum design variables are automatically obtained by using the augmented Lagrange multiplier method, and the static characteristics of the optimally designed sliders are found to be superior to those of the taper-flat sliders of typical configuration over the entire recording band. Results obtained for three taper-flat slider models are reported, showing the effectiveness of the proposed design scheme.

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