S. Jo

Modeling of giant magnetoresistance isolator for high speed digital data transmission utilizing spin valves

Giant magnetoresistance isolator was modeled for effective transmission of high speed digital data, and the output voltage characteristics depending on pulse width of input signal, inductor coil turn, and existence of external circuit of the planar inductor were investigated in time domain. The planar coil was modeled as a lumped element R,L,C circuit and the coil current was calculated using SPICE. The corresponding magnetic field was substituted to the measured magnetoresistance-H curve to obtain the resistance values of the spin valves, which were used to obtain the output voltage wave form of the isolator. Effective maximum transmission speed of 250Mbit∕s was estimated. Even though the coil current wave form was much deformed with damping, the transmitted output voltage wave form was very close to the rectangular wave form of the input signal due to hysteretic characteristics of the spin valves.

Magnetic and Thermal Properties of MoN Underlayer for Spin Valves Depending on Nitrogen Concentration

We incorporated nitrogen in the Mo underlayer and investigated the effect of nitrogen concentration on the magnetic properties and annealing behavior of the spin valve devices. The spin valve structure was Si/SiO2/Mo(MoN)(35Aring)/NiFe(21 Aring)/CoFe(28 Aring)/Cu(22 Aring)/CoFe(18 Aring)/IrMn(65 Aring)/Ta(25Aring). It is concluded that MoN underlayer is magnetically as good as Ta underlayer for N2 gas flow rate of less than 6 sccm

Variations of magnetic properties for various nitrogen concentration in Ta thin films for spin valve structure

In this report, we investigate the change of magnetic property in spin valve devices for various nitrogen concentrations of Ta underlayer. Spin valve samples were deposited on, SiO/sub 2/ substrate by using DC magnetron sputtering system with 2 inch 8 targets. The substrates were-P doped (100) Si wafers with resistivities of 5-6 /spl Omega/-cm 2000 /spl Aring/-thick; thermal oxide was deposited for prohibiting the shunting current effect and the spin valve samples with sample size of 1 inch /spl times/ 1 inch were deposited with linewidth of 200 /spl mu/m and 500 /spl mu/m, respectively. The spin valve structure is Si/SiO/sub 2//Ta(Ta-N)/NiFe/CoFe/Cu/CoFe/FeMn/Ta. Base pressure was less than 2.0 /spl times/ 10/sup -7/ Torr and TaN thin film were deposited with various N/sub 2/ gas flow between 0 and 12 sccm. To obtain the magnetic anisotropy, we apply 600 Oe magnetic field for substrate surrounding. The XRD pattern of the Ta thin film with various gas flow was taken, as well as the resistivity and rms roughness as functions of gas flow ratios.

Modeling of linear isolator utilizing giant magnetoresistance elements

A linear giant magnetoresistive (GMR) isolator was modeled and the output voltage and current in relation to the input current were investigated. The feedback coil current (output current) corresponding to the input coil current closely matched the reported experimental results when the gain of the op-amp modeled was high (500). In the triangular input current wave response, feedback coil current faithfully followed the input current when the slew rate of the input coil current was equal to or lower than that of the op-amp and the input coil current amplitude was within the linear region of the isolator response.

Modeling of GMR linear isolator utilizing spin valves

A linear isolator utilizing giant magnetoresistance spin valves is modeled and its linearity and response time are estimated by electrical circuit analysis. The calculated feedback coil current varies linearly from 0 mA to 16 mA when the input coil current is varied from 5 mA to 21 mA. Nonlinearity of less than /spl plusmn/0.5 mA is observed. As for the rectangular input current wave response, the rise and fall time of the output voltage level are 5 /spl mu/s each, which are limited by the slew rate of the operational amplifier.

Giant magnetoresistance and temperature characteristics of bottom spin valves having very thin Cu spacers

Summary form only given. Magnetoresistance and temperature characteristics of bottom spin valves having very thin Cu spacers are reported. The spin valves were deposited using a DC magnetron sputter deposition system having a base pressure below 2/spl times/10/sup -9/ Torr. The spin valve films were annealed at 220/spl deg/C for 2 hours in 2 kOe of magnetic field. Variation of magnetoresistance (MR) ratio with respect to Cu spacer thickness is shown for underlayer55/spl Aring//NiFe10/spl Aring//IrMn70/spl Aring//CoFe10/spl Aring//Ru4/spl Aring// CoFe13/spl Aring//Cu/CoFe10/spl Aring//NiFe10/spl Aring//Ta50/spl Aring/ bottom spin valve structure. MR ratio was 11.7% at the Cu thickness of 18 /spl Aring/ and decreased to 9.8% at 12 /spl Aring/ due to the increase of the interlayer coupling field from 14 Oe to 248 Oe. Then, MR ratio increased and reached a maximum of 11.9% at the Cu thickness of 10.4 /spl Aring/, which corresponded to 12 Oe of antiferromagnetic coupling field. Unlike the top spin valves reported earlier by the authors, the dipping of the MR ratio near the zero coupling field was not observed. Also shown is the sheet resistance change (DRs) vs. Cu spacer thickness for the same bottom spin valves. DRs reached 4.22 /spl Omega//Sq at the Cu thickness of 10 /spl Aring/ compared with 3.09 /spl Omega//Sq at the Cu thickness of 18 /spl Aring/. They show that the temperature dependence of MR ratio and DRs up to 200/spl deg/C for underlayer55/spl Aring//NiFe10/spl Aring//IrMn70 /spl Aring//CoFe20/spl Aring//Ru4/spl Aring//CoFe23/spl Aring//Cu10.4/spl Aring//CoFe20/spl Aring//NiFe10/spl Aring//Ta50/spl Aring/ films. MR ratio decreased from 13.0% to 7.3% and DRs from 3.16 /spl Omega//Sq to 2.25 /spl Omega//Sq as the temperature increased from 25/spl deg/C to 200/spl deg/C. Thus, these bottom spin valves having very thin Cu spacers exibit high MR ratio, high DRs and excellent temperature characteristics.

Jitter simulation of readout signal including adjacent track mark profile variations of optical disks

The crosstalk, which is defined as interference noises and jitters as well as signal decrease due to adjacent tracks can become a major contributor to total noise, as track pitches get reduced in order to achieve higher track density. To increase the track density, land • groove recording method is used, which can increase the recording density by a factor of two if the crosstalk and crosserasing problems can be avoided. Also, mark edge recording method can cause considerable jitters if the mark profile variations are significant.

Magnetic bubble collapse in ion implanted bubble propagation tracks

The magnetic-bubble collapse fields along the good, bad, and super tracks fabricated on a conventional garnet film and a nearly isotropic garnet film were measured for a cycle of rotating in-plane field. Bubble potential well curves were obtained from the bubble collapse fields and compared with each other. It was found that magnetic bubbles encounter the strongest repulsively charged walls twice during a cycle of in-plane driving field when they reside in the cusps of bad tracks. Therefore, bad tracks exhibit the shallowest potential well curves and, thus, the lowest collapse fields among the three differently oriented (good, bad, and super) tracks. When a magnetostrictively nearly isotropic film is used instead of a strongly anisotropic film, the repulsively charged walls are much weaker and the bubble potential well depths at the cusps of bad tracks become much deeper. This explains the increase of bubble collapse fields reported earlier in the bad tracks fabricated on a nearly isotropic film. >