Transient Thermal Response of the Media by Free Space Laser Heating in Heat Assisted Magnetic Recording

Heat assisted magnetic recording (HAMR) promises to deliver higher storage areal density than the current perpendicular magnetic recording (PMR) product. A laser is introduced to the HAMR system to heat the high coercively magnetic media above the Curie temperature (Tc) which is as high as 750 K in order to enable magnetic writing. The thermal response of the media becomes very critical for the success of the data writing process. In this paper, a new method is proposed to understand the transient thermal behavior of the HAMR media. The temperature response of the media is measured based on thermal erasure of the magnetically written signal. A lumped model is built to simplify the heat conduction problem to understand the transient thermal response. Finite element modeling (FEM) is implemented to simulate the transient thermal response of the media due to the laser pulse heating. The experimental and simulation results show fairly good agreement.

Effect of the Acoustic Field Geometric Parameters on Planar Array Acoustic Levitator

Acoustic contactless manipulation technique that is capable of transporting and manipulating of small particles is highly attractive in studying of many physical phenomena and biochemical processes. The finite element method is used to study the effect of the acoustic field geometric parameters on the acoustic levitator consisting of the transducer planar array and a reflector. The optimal acoustic chamber height and the distances between the array elements are determined through the numerical simulation. The analytical results provide the geometry parameters that can be used in optimizing acoustic chamber for particles transportation.

Superlubricity Relevant in Hard Disk Drive Applications

Reduction of head-media spacing (HMS) keeps crucial during the increase of areal density of hard disk drives (HDD). The design of hard disk drive with a superlubric interface is reported with two schemes for HDI design to realize superlubricity. For the first scheme, the DLC layer is kept on the disk while removing the lubricant layer. The DLC layer on the transducer is replaced by graphene-like layer. The direct contact between head and disk could reduce the HMS to about 2.3 nm. For the second scheme, the DLC layer on disk is further replaced by graphene and the HMS could be reduced to below 1 nm. For the first scheme, the basic proof of concept experiments are conducted using micro-scale graphite island samples. Ultralow COF, with the average of 0.0344 on the interface of single crystalline graphite surface and DLC substrate is demonstrated by AFM. What’s more, the temperature dependence of friction between single crystalline graphite and DLC is measured by micro-force sensor mounted on micro-manipulator. The results show that heating helps to significantly decrease the friction. Desorption of contaminants along the interface is speculated to be the key mechanism for temperature dependence of friction. This work provides the concept of large-scale superlubricity relevant in HDD applications, which could be a promising technology to ultimately reduce HMS for future HDI development.

A Study of Antiferromagnetic-Pinned Multiferroic Composites Nano Read Head

This paper presents a study of the effect of antiferromagnetic (AFM) integration on the nano AFM-pinned multiferroic (MF) composites structure. The nano MF composites structure is a potential candidate for a future magnetic read head. The simulation of the AFM/ferromagnetic (FM) bilayers characteristics and the evaluation of the magnetoelectric (ME) effect induced in the 1-dimensional (1D) L-T mode model of AFM-pinned structure of AFM/FM/Ferroelectric (FE)/FM/AFM are performed. FM, FE, and two types of AFM materials are Terfenol-D, lead zirconate titanate (PZT), and PtMn and Cr2O3, respectively. The magnetoelectric (ME) effect is investigated using the 1D standard square law. Magnetic-field induced strain in the FM layer, piezoelectric response of the PZT layer, and the ME coefficient are determined. Specifically, the influence of AFM on the MF composites structure for various AFM thicknesses is of interest. It is found that the maximum electric field and potential across the PZT layer are achieved at 2.7 nm thick of PtMn. The result is well agreed by associated magnetic field-induced strain and ME coefficient.

Disk Lubricants of Ultimate Design

In disk drives of current generation, the thickness of the disk lubricant has been reduced to the level of a sub-monomolecular film. For a mono- or a sub-monomolecular film of a perfluoropolyether terminated with a primary hydroxyl unit at both ends, each lubricant molecular chain is chemically bound to the carbon substrate at both termini, and if it has a hydrocarbon sector inserted at its center, the hydrocarbon sectors would assemble at the top of the film. They are thus poised most aptly to react as a Lewis base (an electron donor) to the Lewis acid centers on the slider thus abating the Lewis acid-catalyzed lubricant degradation.

Design and Control of a Frog-Inspired Swimming Leg Powered by Pneumatic Muscle

According to the shortages of previous generation of frog inspired robot, antagonistic joint based frog inspired leg was designed. With the multi-DOFs of hip, knee and ankle, the designed leg was able to perform various frog swimming modes. The dynamic model of antagonistic joint based on advanced pneumatic muscle model was established in MATLAB/Simulink environment. Besides, the servo control strategy of joint angle was studied based on the dynamic model of antagonistic joint. The PID and self-tuning fuzzy control were utilized to control the antagonistic joint. According to different swimming modes, joint trajectories of hip, knee and ankle were created by inverse kinematics based on the frog swimming mechanism. Therefore, the leg was controlled by the separated controls of hip, knee and ankle joints. Feasibility of pneumatic antagonistic joint control was validated via step response experiments with different loads. Finally, the experiment platform was established to carry swimming experiments with the developed frog-inspired swimming leg. The feasibility of antagonistic frog inspired swimming leg driven by pneumatic muscles was validated.

IPI Noise Reduction by Image Mask Using DNA Coding Method in Holographic Data Storage System

A holographic data storage system (HDSS) is very important field in the storage system device. Many researchers study the HDSS about image processing algorithm for reduction of image noise. In this work, we proposed an intelligence virtual mask, parameter values of virtual image mask generated using DNA coding method, it is available to decrease the IPI noise in HDSS. In this paper, an intensity distribution of laser beam in our HDSS is controlled by the virtual mask with an intelligence algorithm. The virtual mask value is changed arbitrarily in real-time with suggested DNA coding method in the HDSS.

Vibration Reduction of MLCCS Using Vibration-Canceling Effects of Poling Process

MLCC vibrates due to its piezoelectric characteristics and it makes circuit board vibrate and lead to acoustic noise. In order to reduce vibration, piezoelectric coefficient should be reduced. In this study, poling process was used to decrease piezoelectric coefficient. Due to the electrostriction coefficient, response at fundamental frequency can be cancelled by applying voltage to opposite direction. Through the experiment, vibration-cancelling voltage increases as the poling voltage increases. Also, vibration-cancelling voltage increase inversely proportion to MLCC’s capacitance. By applying proper DC bias after poling process, vibration can be reduced.

Formation and Control of a Rotating Magnetic Field in Magnetic Abrasive Finishing

Surface finishing is the final operation in manufacturing processes and it costs around 15% of the total manufacturing cost [1]. A high quality surface with very low values of surface roughness and high accuracy are required for some products in many applications. These characteristics are required especially for products with a complex shape which are made from advanced materials such as alloys of hard materials, glass, and ceramics.

A New Small-Sized Non-Dispersive Infrared (NDIR) Sensor and its Drive/Readout Circuits

A new miniaturized, non-dispersive, infrared (NDIR) sensor for CO2 intended to be installed in mobile phones and its drive/readout circuits are presented in this study. A typical NDIR sensor consists of three main components; an infrared (IR) light-emitter (light source), a gas chamber, a photo detector (PD) light receiver) and the associated drive/readout circuits. The geometry of the gas chamber is optimized to minimize the total module size to approximately 10 mm × 5 mm × 5 mm, which is much smaller than commercially-available gas sensors. Driver and readout circuits are successfully designed and taped out. The driver circuit intends to generate pulse width modulation (PWM) signal to control proper dimming of LED. The readout circuit, which acquires small signal from photo detector then converts to digital values, includes amplifier, low pass filter and analog-to-digital converter (ADC). The proposed circuit is fabricated by the TSMC 0.35-μm CMOS process, where the area is 4.527 mm2 while power consumption is 60.16 mW for the whole chip. The resolution is less than 12 ppm along with time constant is 0.1 sec.