Abstract: According to the method for preparation of ultrathin magnetic layer on semiconductor of this invention, a non-ferromagnetic metal buffer layer thinner than 40 ML is formed on the semiconductor substrate on which the magnetic layer is to be prepared. The thickness of the non-ferromagnetic metal buffer layer may be 0.5-9 ML, preferably 1-8 ML, most preferably 1.5-6 ML. Thereafter, the magnetic layer is formed on said non-ferromagnetic metal buffer layer. The thickness of the magnetic layer so prepared may be less than 40 ML, close to the limitation of ultrathin. Material for the non-ferromagnetic metal buffer layer is preferably a metal or metal alloy that is immiscible with the magnetic layer when the magnetic layer is formed on the buffer layer. In the embodiments of the present invention, the non-ferromagnetic metal is silver, while material of the magnetic layer is cobalt. This invention also discloses the magnetic structure so prepared.