CoPt nanocomposite films: microstructure and magnetic behavior

Summary form only given. CoPt is an advanced magnetic material with attributes of both applied and basic interest. The formation of the high magnetocrystalline anisotropy, chemically-ordered L1/sub 0/ CoPt phase occurs through a disorder-order transformation from the parent, chemically-disordered A1 phase. In the A1 structure, the occupation probability of a given atom site by either Co or Pt is equal, while in the ordered structure each atomic site is occupied by specific atomic species. The ordering results in alternating planes of Pt and Co along any one of the three original cube axes, leading to three ordered variants. When deposited at room temperature, CoPt forms in the magnetically-soft Al structure, with the magnetically-hard L1/sub 0/ structure obtained by annealing. Thus, ferromagnetic "exchange-spring" nanocomposite films of A1+L1/sub 0/ CoPt with varying amounts of the two constituents can be obtained by tailoring the anneal. In this work, we provide new, detailed information on the temporal evolution of the L1/sub 0/ domain size and its relation to grain size in CoPt films. Development of coercivity is correlated to the development of the ordered structure.