A magnetic recording disk has an antiferromagnetically-coupled structure that has three lower ferromagnetic layers and an upper ferromagnetic layer, all four ferromagnetic layers being antiferromagnetically-coupled together across corresponding antiferromagnetically-coupling layers. The invention thus relates to the plants, seeds and tissue cultures of the variety CV594762, and to methods for producing a corn plant produced by crossing a corn plant of variety CV594762 with itself or with another corn plant, such as a plant of another variety. The overall length of the handle, with respect to the head of the hammer, is therefore adjustable. The limit is compared to a tuning value which corresponds to a desired calibration frequency.