Although I cannot claim any aptitude toward physics, I cannot resist being 'drawn'
to this fascinating thread!! As always, Jens poses intriguing questions on most unusual topics.
The subject of metallurgy as applied in the blades of edged weapons has often been discussed here, as has the more esoteric aspect of the use of meteoric iron, but little concerning magnetic properties in blades has been considered. The exception, as has been noted by Nechesh, was his post of several years ago and is linked in his previous post.
The presence of lodestones, or magnetite with the iron attracting properties discussed, has been known since early Greek times. Other than being considered an interesting anomaly, it does not seem that this curious material keyed any special purpose. One of the primary features of magnetism has been its use in navigation and the development of the compass, but this apparantly did not occur until about the end of the 11th century AD in China.
There are no references in old Greek and Roman literature about the directive properties of magnetic material (the term magnet came from the Greek term for people called the Magnetes who lived in Magnesia,in Thessaly).
The first use of crude compasses at sea is reported by the Chinese, and believed to refer to those used by Muslim traders in regions between Canton and Sumatra in latter 11th c.
There was little attention given to magnetic navigation in the west until the latter 16th century with most attention applied to celestial navigation, aside from isolated interest.
Since lodestone, or magnetite was so little known through these periods of history, and certain ferromagnetic metals such as nickel and cobalt were not identified until the 18th and 19th centuries, it does not seem that there would have been any deliberate attention given to applying magnetic properties in forged steel in early times. It does seem however, that the occurence of such forces would have inspired mystical and occult attention, along with other natural phenomenon such as meteoric iron.
Although as I have noted, I cannot add much to the discussion on the physical properties of magnetism, I just wanted to share some observations that pertain to the historical perspective,