Advances in magnetoresistive materials have recently enabled magnetic recording heads to achieve higher levels of performance. This article describes why higher signal outputs are necessary for improvements to be made in areal density. The requirements for recording at an areal density of 16 Mb/mm 2 ͑10 Gb/in. 2 ͒ are discussed with regards to both the channel and the head design. Increased output from new multilayer magnetoresistive materials is required to counteract the decrease in output due to the reduction in the size of the head geometry. An areal density of 16 Mb/mm 2 is shown to be feasible with spin valve recording heads using materials with magnetoresistance ratios of 10%. Fabrication issues relating to the manufacturing of these materials are shown to be more stringent than previously required.

Low power, fast speed, small size, wide temperature range, and common-mode-noise-rejection capability are some of the attributes of magnetoresistive devices for galvanic isolation over conventional devices such as optical and capacitive devices. We have fabricated prototype galvanic isolators using spin-dependent tunneling materials. The tunnel junctions have been deposited by rf diode sputtering and the Al2O3 barriers are formed by depositing a thin layer of Al, then oxidizing it with oxygen contained plasma. The junctions are then patterned using photolithography techniques to define the pinned and free layers separately. A series of tunnel junctions are connected in a Wheatstone bridge form and are fabricated directly on top of the integrated circuit (IC) electronics that are used to process the signals from the bridge. In its core magnetics design, this digital device simply employs a one-bit memory cell capable of operating at 5 V. The functions of the devices are tested using a function generator, an IC driver chip, a probe station, two dc power supplies, and a high-speed network analyzer. The power consumption for the isolator is <1 mW when operating at 2 MHz, a factor of 10 lower than the giant magnetoresistance product of similar functions. The operating speed of this device reaches 60 MHz, limited by the design of the electronics.