Permalloy Structures Research Articles

Complementary permalloy bubble propagation structure

Bubble propagation has been achieved in a novel permalloy structure made up of a pattern and its complement. The pattern is defined by a step in the spacer on top of which the permalloy is deposited leaving the permalloy in two levels. Bubbles are propagated under the influence of the fringe field generated at the permalloy step by a rotating in-plane field. The fabrication of the devices is as follows: A spacer layer of SiO 2 (3000A) is first deposited followed by the application of photoresist (1.5μm). The photoresist is patterned such that undeveloped resist is left in the area of low permalloy. A layer of Schott glass (4000 to 6000A) is deposited over the wafer followed by lifting off the photoresist. This leaves Schott glass layer in the area of high permalloy. A permalloy layer (15OO to 2500A) is deposited over the entire device area. Devices of 10μm period and 2μm minimum feature were fabricated (see photo) and tested. Propagation margins >10% were obtained with 35 to 50 Oe drive fields.

SEM observations of domain configurations in thin-film head pole structures

An investigation was made of the domain configurations in uniaxial anisotropic permalloy pole structures for integrated thin-film heads utilizing the SEM type-II magnetic contrast mode. The technique was compared with other viable methods including Kerr magneto-optics and the ferrofluid colloid. Type II was found to be superior for dynamic and high-magnification studies. ac demagnetized, partially saturated, and remanent configurations were observed in poles of different geometries, after magnetization in both easy and hard directions. A comparison was made with the domain configuration in double-layer permalloy structures. In the study of complete integrated heads, only the top pole domain configuration was observable using the ferrofluid colloid method, while with 200-keV type II, the complete magnetic circuit domain structure was imaged. The effect of subsequent head processing on easy axis alignment was found to be minimal.

Complementary permalloy bubble propagation structure

Bubble propagation has been achieved in a novel permalloy structure made up of a pattern and its complement. The pattern is defined by a step in the spacer on top of which the permalloy is deposited leaving the permalloy in two levels. Bubbles are propagated under the influence of the fringe field generated at the permalloy step by a rotating in-plane field. The fabrication of the devices is as follows: A spacer layer of SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> (3000Å) is first deposited followed by the application of photoresist (1.5μm). The photoresist is patterned such that undeveloped resist is left in the area of low permalloy. A layer of Schott glass (4000 to 6000Å) is deposited over the wafer followed by lifting off the photoresist. This leaves Schott glass layer in the area of high permalloy. A permalloy layer (15OO to 2500Å) is deposited over the entire device area. Devices of 10μm period and 2μm minimum feature were fabricated (see photo) and tested. Propagation margins >10% were obtained with 35 to 50 Oe drive fields.

High-frequency propagation and failure of asymmetric half-disk field access magnetic bubble device elements

High-frequency propagation characteristics and failure modes in 14-μm period, 1.8-μm gap, asymmetric half-disk field-access device were studied using a high-speed optical sampling technique. Propagation elements as well as normal and hand gun corners and chevron structures were included. The operating bias margin at 1MHz, for a structure that had 1.2 MHz as highest possible frequency, was about half of the margin for frequencies of 200 kHz and below. The phase lag between the bubble leading wall and the instantaneous rotating field direction was nearly 90° as the bubble moved through the center of the element where the lag was the greatest. The peak velocity of the leading wall of 55 m/s and the trailing wall of 46 m/s is attributed to bubble interaction with the Permalloy structure creating a ∼125 Oe in-plane field that greatly increases the free bubble saturation velocity.

Coercive force of electrodeposited NiFe on top of conductors for SLM bubble device applications

Reduction of the bubble size in bubble devices made evident that the permalloy used in the structure has to comply with very strict specifications of coereivity and remanence. This paper reports on a study aimed at minimizing the Hc of permalloy electroplated on top of thick gold conductor, such as is used in the SLM, conductor first, devices. The coercive force of electroplated permalloy was studied as a function of the type of the underlying metal conductor, its thickness, and its surface characteristics as determined by the type and rate of deposition. Also studied were the correlation between Hc and the electroplated permalloy thickness, and the effect of annealing on the coercive force. It was found that reproducibly the best magnetic properties of permalloy are obtained when a thin layer of permalloy is evaporated on the gold conductor prior to electrodeposition of the permalloy structure.

Mode conversion in magneto-optic waveguides subjected to a periodic Permalloy structure

A new method to achieve periodic reversals of magnetization, necessary to attain high mode conversion efficiencies in magneto-optic waveguides, is described. It is acomplished by means of a periodic Permalloy structure overlaying the optical propagation path. With proper bias fields, we have observed an optimum dc conversion efficiency of 80±2% at 1.15 μm in a Gd0.5Ga1 iron garnet film guide.