K. Komenou

Magnetization, strain, and anisotropy field of Ne+ and H+ ion‐implanted layers in bubble garnet films

The effects of the implantation dose and annealing on magnetization (4πMs), lattice constant strain (Δd/d), and change in the anisotropy field (ΔHK) of a layer implanted with Ne+ or H+ ions in bubble garnet films have been investigated using a vibrating sample magnetometer (VSM), the double crystal x‐ray technique, and ferromagnetic resonance measurements. The magnetic and crystalline properties of Ne+ or H+ ion‐implanted layers were quite different. Saturation magnetization of the H+ ion‐implanted layer decreased gradually with Δd/d beyond 1%, while that of the Ne+ ion‐implanted layer decreased abruptly above 1%. ΔHK of the Ne+ ion‐implanted layer was proportional to Δd/d up to a saturation point of about 1%; however, ΔHK of the H+ ion‐implanted layer continued to increase after Δd/d passed 1%. The other distinct difference between the H+ and Ne+ ion‐implanted specimens was the temperature necessary to obtain annealing effects. In the H+ ion‐implanted layer, annealing in the lower (around 200 °C) tempera...

Magnetic and crystalline properties of ion-implanted garnet films with plasma exposure

The implantation induced anisotropy field change, ΔHk, and lattice strain, Δd/d, in ion implanted films have been found to be enhanced considerably by exposing films to plasma of H 2 , He, Ne and Ar gases in the substrate temperature greater than 100°C. The enhanced ΔHk is twice as large as the as-implanted value in typical experiments, and it is comparable to the ΔHk of the hydrogen ion implanted layer. The enhanced ΔHk of the exposed film decreases greatly with increasing annealing temperature, but this can be prevented coating the surface with an SiO 2 layer. The changes of ΔHk profiles in plasma exposure are obtained by FMR technique. ΔHk is enhanced not only at the surface but also deep in the implanted layer. The origin of this effect is probably ascribed to the diffusion of the residual hydrogen into the implanted layer.

Development of an ion implanted bubble device with 4 µm period

A 4 μm period ion implanted bubble device has been developed employing 1 μm bubble single layer film. The design and characterization of a transfer-in gate are described. The effect of the pulse shape on operating margins has been investigated, and an auxiliary pulse added to the transfer pulse to greatly improve gate performance. This newly designed transfer-in gate has also been successfully operated as a bidirectional transfer gate. In order to decrease the access time of large capacity chips, a highly efficient method of detection at high frequencies has been devised. Characterization of the device at 300 kHz is presented.

Permalloy film for single‐level detector with high sensitivity

The use of single‐level circuit has simplified the fabrication process. A thick film detector, however, has weak points; it has a low detection efficiency due to the large demagnetizing field and unfavorable noise is inherent in it. The authors study the magnetoresistive characteristics of permalloy films and find out the detectors with high senstitivity, selecting the appropriate evaporation conditions. The significant results are as follows. (1) The large detection voltage is obtained from those elements whose magnetic easy axis deviates from the shape anisotropy direction, which serves to reduce the effective anisotropy field. (2) This angle of deviation α is increased with the raising of the substrate temperature and with the lowering of the evaporation rate. For example, α=60° at 310°C, 3AC, 3A/sec, and α=0° at 250°C, 10A/sec. (3) Detection performances are investigated on the 30‐column serpentine detector using 3 μm stripe domain width of (YGdYb)3(GaFe)5012 with a 4π Ms of 260 Gauss. The signal volt...

Characterization of 1.5 µm Bubble Devices built on low Magnetization Garnet Films for minimizing Drive Field

Minimization of the drive field by using garnet films with low magnetization has been studied for 1.5 µm diameter bubble devices. Test chips designed on 8 µm period half disks with a 1 µm minimum feature have been built on three sets of garnet films with different magnetizations of typically 350, 400 and 490 Gauss (G) by using planar processing. Results for devices made on garnet films of various magnetization show that the normalized bias margins increase with decreasing magnetization and minimum drive fields for these devices decrease from 30 to 20 Oe. Furthermore, when the drive field was defined as the field necessary to produce normalized bias margins of 20% for propagation and 15% for the stretcher, we obtained a drive field value of 30 to 60 Oe for a magnetization of 350 to 490 G.

Design and characteristics of 4 µm period ion-implanted bubble devices with major line block replicate gate

A block replicate gate composed of an ion-implanted minor loop and a permalloy major line has been developed for 4 μm period bubble devices. This gate employs a hybrid permalloy and ion-implanted bubble device with no junction between the patterns. Test chips incorporating this replicate gate, the folded minor loop, and the cusp-to-cusp bidirectional transfer gate have been fabricated and characterized for a 100 kHz triangular drive field. A bias field margin of 30 Oe was obtained at 70 Oe ± 10 % peak drive field.

Cusp-to-cusp transfer gate using folded minor loop organization for ion-implanted bubble devices

Ion-implanted bubble devices using the folded minor loop organization have been developed to relax spatial restrictions on function pattern design and improve the reliability of gate conductors. A cusp-to-cusp transfer gate using this organization has been designed in which bubbles are transferred between the cusps of the propagation patterns of the major line and minor loops. A 180° inside turn has also been designed in order to realize the folded minor loop organization. Test chips incorporating 4 μm period devices with the folded minor loop organization have been fabricated and characterized for a 100 kHz triangular drive field.

Design of a block replicate gate for ion-implanted bubble devices

A block replicate gate has been designed for 4 μm period ion-implanted bubble devices. The gate consists of a conductor lying across a V-shaped unimplanted pattern between the minor loop end and the major line. Replication is accomplished by stretching the bubble with a stretch pulse through the conductor, cutting the domain by means of the charged wall formed at the edge of the V-shaped pattern together with a pulse of short duration, then restoring the bubble to the original condition by means of another stretch pulse. A bias field margin of 20 Oe was obtained with an error rate of 10-5for a 100 kHz, 80 Oe peak triangular drive field.

Design of 2 µm-period minor loops in hybrid bubble memory devices

The folded minor loops for hybrid bubble memory devices with 2 μm period propagation tracks have been developed by designing junctions between permalloy and implanted tracks, as well as designing inside and outside turns. The junction from the permalloy to the implanted tracks has been successfully designed utilizing the deep potential well of the permalloy pattern for bubbles to cross the boundary. The junctions were operated successfully for the first time using 0.6 μm bubbles optimized for 2 μm period tracks. We also designed the outside and inside turns considering the demagnetizing field and the crystalline axis of the implanted layer respectively. As a result, good bias margins of turns were obtained. The bias field levels of all elements agreed quite satisfactorily. Overall bias field margins of 40 Oe has been obtained with the quasi-static drive field of 70 Oe.

Fabrication and Operating Characteristics of Ion-Implanted Bubble Memory Chips for a 16M-Bit Device

A test chip using ion-implanted functions for a 16-Mbit bubble memory device has been designed, fabricated and characterized. A new delineation process for ion-implanted tracks using SiO2 ion-implantation masks is effective for reducing defects in minor loops. As a result, a bias margin of 22 Oe was obtained for minor loop bubble propagation. Test chip operation over a wide temperature range, from ¿25°C to 80°C, has been realized.