Thermally stable high-moment FeCo/IrMn soft underlayers for perpendicular media

High-moment FeCo/IrMn exchange-coupled multilayer films were demonstrated to have outstanding characteristics as soft underlayers for perpendicular media. However, their thermal stability was not sufficient to maintain the single-domain condition above 75(degree)C. Here, it is reported that an underlayer of (beta)-Ta (200) considerably enhanced the texture in IrMn [111] and FeCo [110] films. An improved structure was found to be glass/Ta(20 nm)/Cu(20 nm)/IrMn(10 nm)/[FeCo(50 nm)/IrMn(10 nm)]/sub 4//FeCo(25 nm), which showed significantly enhanced thermal stability without deterioration in other characteristics. There was no irreversible reduction in the exchange-bias field after the thermal cycle, an increase in the maximum temperature T/sub max/ to maintain the single-domain condition of the exchange-bias field greater than the coercivity from 75(degree)C to 150(degree)C, and an increase in the blocking temperature from 175(degree)C to above 250(degree)C. Annealing at 225(degree)C with an orienting field parallel to the pinned direction further enhanced the single-domain condition, resulting in an increase in T/sub max/ from 150(degree)C to 220(degree)C.