Anan Kruesubthaworn

A novel technique to detect effects of electromagnetic interference by electrostatic discharge simulator to test parameters of tunneling magnetoresistive read heads

Electrostatic discharge (ESD) has been a significant problem in the manufacturing processes of the magnetic recording head technologies for many years. Besides direct discharge damage, ESD can also generate electromagnetic interference (EMI) which could possibly cause failure in magnetic read heads. The aims of this work are to measure the EMI from ESD simulator based on the standard IEC 61000-4-2 and to investigate the effects of EMI on tunneling magnetoresistive (TMR) read heads. The discharge current and the EMI generated by ESD simulator are measured in the experiment. Also, the EMI is applied to the TMR read heads at various amplitudes and distances in order to evaluate the changes of read head parameters including the bit error rate, resistance, read back signal amplitude, and asymmetry parameter of the head. The results show that the discharge current waveform is consistent with the IEC standard current waveform. In addition, it is found that the EMI is insufficient to cause a permanent change of t...

Magnetic Instability in Tunneling Magnetoresistive Heads Due to Temperature Increase During Electrostatic Discharge

Recently, there has been a growing interest in the effects of electrostatic discharge (ESD) failure on tunneling magnetoresistive (TMR) recording heads because it directly affects reliability in manufacturing of these heads. Therefore, we study the magnetic degradation in TMR junctions caused by the temperature increase using three different ESD models. A 3-D finite-element method is used for analyzing the spatial and temporal profiles of the temperature during the discharge. The results from the three models show that, although the highest temperature occurs in the MgO barrier layer, the initial magnetic modification likely arises in the IrMn antiferromagnetic layer due to its low Néel temperature. We also found that the increase in temperature is proportional to the square of the ESD voltage. The magnetic instability of the antiferromagnetic layer due to the ESD effect is the important parameter realized for development of the future TMR devices.

An EMI Immunity Study of TMR Heads in Quasi-Static Tester due to the Direction of Sweeping Frequency

This report aims to investigate a comparative effect of Electromagnetic Interference (EMI) on recording heads due to sweeping directions of low-to-high and high-to-low frequencies. Four selected Quasi-Static Tester (QST) parameters; MR resistance, MR amplitude asymmetry, Barkhausen noise and Hysteresis, are used for monitoring the effect of EMI on Head Gimbal Assembly (HGA). It is undoubtedly found that the Asymmetry and Hysteresis parameters provide insufficient indication of EMI effect for both sweeping frequency directions. On the other hand, it is discovered that the sweeping direction of the low-to-high frequency is more effective to two test parameters; MR resistance and Barkhausen noise, than the other direction. The dramatic energy accumulation is possibly explained this phenomenon but this energy level is not high enough to cause the Hysteresis change.

Crosstalk Suppression in High Data Rate and High Density Hard Disk Drive Interconnects Using Magnetic Composites

Abstract Due to the increasing data transfer rates in hard disk drives, the crosstalk has become a source of operation failures during electrical and magnetic testing. In order to reduce this detrimental effect, the differential mode signal system of high-speed and high-density interconnects based on a new magnetic technique is proposed. The scattering parameters are evaluated in terms of the crosstalk and the transmission parameters, and then calculated using the 3D full wave simulation software. From the results, it is found that the proposed technique can suppress the near-end crosstalk and far-end crosstalk in a wide range of 1–20 GHz. In addition, the transmission signal levels from the proposed structure are still comparable to the conventional structure. Hence, the proposed technique provides an effective reduction of crosstalk, while maintaining the comparable transmission signal in a wide range of frequency.

Anomalous magnetic responsiveness of giant magnetoresistive heads under specific electromagnetic interference frequencies using quasistatic tester

The giant magnetoresistive (GMR) heads have been used in the computer industry for decade. Recently, the anomalous performance caused by cell phones or external electromagnetic interference (EMI) is reported [V. Kraz and A. Wallash, J. Electrost. 54, 39 (2002)]; [Kruesubthaworn et al., J. Magn. Magn. Mater. 316, e142 (2007)] This prompts an experimental study of an anomalous magnetic disturbance to the heads under ascending and descending frequency variations. The rf generator with predetermined output is set for 30–1000MHz swept frequency in both directions, with the antenna being horizontal and vertical orientations. Five quasistatic tester (QST) parameters; magnetoresistive (MR) resistance, MR amplitude, asymmetry, Barkhausen noise, and hysteresis are used as markers in the EMI sensitivity study of head gimbal assembly. It is found that the worst change of MR amplitude is 10.2% (marginally over the norm), which occurs at 910MHz during ascending swept frequency and horizontal polarization. The largest v...

The temperature and electromagnetic field distributions of heat-assisted magnetic recording for bit-patterned media at ultrahigh areal density

In this paper, the temperature and electromagnetic field distributions for bit-patterned media (BPM) with heat-assisted writing technology at areal density of 6.54–17.92 Tb/in2 are investigated by the finite integral technique method. We have found that the BPM can confine temperature better than continuous media. The temperature ratio of neighbor bits to heating bit of BPM at areal density of 6.54–7.69 Tb/in2 is lower than 65% and increases with increasing areal density. The electric field direction is toward the bit and the magnetic field circulates around the heating bit. In addition, the electric field of BPM is the same pattern as continuous media at areal density of 13.17 Tb/in2 or above.

Automation Broadcast Radio Controlled by Using Audio Mute Clock

This paper presents distribution and automation radio broadcasting organization that is operated by international radio stations such as Voice of America (VOA) using the control center that must rely on the cost of the electrical and electronic instruments and the operation and must be very high dependency computer technology that is relative to clock and must be done regularly to ensure the accuracy. The changing schedule of automation radio broadcasting controlled by programmable logic controller, PLC [1] and the master clock [2] is time in second is required to execute the PLC program for every changing of the schedule program. The ideology of silence of sound signal (Audio Mute) is used when each program ends instead using the master clock to execute the PLC program for changing the schedule radio program. The application of audio mute for changing new schedule when each program ends can be compared with the using the master clock controlling the PLC will be also minimum deviation of the time that will impact on automation radio broadcasting.

THERMAL IMAGE REFINEMENT APPROACH FOR SCRATCHES ON A MAGNETIC DISK EVALUATED AT VARIOUS ANGLES

Scratch damage on magnetic disks is a major problem in the hard drive industry as it affects the reliability. To address this problem, it is therefore necessary to apply advanced detection techniques. To enhance micro-scratch detection, an infrared camera capturing technique based on heat radiation is proposed in this article. Nevertheless, the captured thermal images may be invisible due to the Narcissus effect as a dark region covering the interested areas. An approach of thermal image refinement is also presented by heating the magnetic disk at various angles of magnetic disk and CaF2 external zoom lens. The thermal image and the emissivity ratio are used to indicate suitable angles and heating times at which the scratch can be clearly detected. It is found that the rotation of the CaF2 external zoom lens can assist the detection of a micro-sized scratch and a heating time of 10 s is sufficient to clearly show scratches if the magnetic disk is set to be aligned in parallel with the CaF2 external zoom lens.

Electromagnetic Interference Effects on Stability of Tunneling Magnetoresistive Read Heads

We used micromagnetic simulations to investigate the effects of electromagnetic interference (EMI) caused by electrostatic discharge on the stability of tunneling magnetoresistive (TMR) read heads based on International Electrotechnical Commission standard 61000-4-2. In simulation, EMI was applied to TMR heads between 0.1 cm and 2 cm from the source, and magnetization fluctuations and induced magnetic noise were evaluated. Although EMI can induce spin-transfer torque in the heads, it causes little change in the magnetization orientation and no noticeable influence on the readback signal or signal-to-noise ratio of the heads.

Angular Dependence of Spin Transfer Switching in Spin Valve Nanopillar Based Heusler Alloy

The spin transfer induced magnetization switching in current perpendicular-to-the-plane spin valve nanopillar based Co2FeAl0.5Si0.5 Heusler alloy with varying the initial angles of the magnetization of sensing layer, , was investigated via macrospin simulations. The effects of an in-plane magnetic field, , on the switching behavior were also evaluated. The magnetization switching was excited by spin polarized switching current, . The time varying magnetization was computed by the Landau-Lifshitz-Gilbert-Slonczewski equation, while the spin transfer induced noise was examined by using the power spectral density analysis. It was found that should be narrowly initialized since this configuration produces the small noise during the switching. Also, the negative produced more uniform switching than the positive due to existence of ferromagnetic exchange coupling. When was presented, the noise generated at low frequencies could be suppressed, and then the switching behavior became more uniform. In addition, the results indicated that the noise configuration could be explained by the physical dynamic of magnetization behavior. Hence, the spin transfer induced noise needs to be minimized in order to improve the performance of spin transfer torque random access memory for high density recording.