Study of ferro-antiferromagnetic transition in [001]-oriented L10 FePt1-xRhx film.

Magnetic properties of [001]-oriented L1₀ FePt_1-xRh_x films (t_FePtRh=6.12 nm) with Rh composition (x) of 0≤x≤0.40 were studied, and the magnetic phase in a composition-temperature plane was investigated. At room temperature, the films with 0≤x≤0.32 were in a ferromagnetic (FM) phase with a coercivity of several kilo-oersteds, and the films with 0.34≤x≤0.40 were in an antiferromagnetic (AF) phase. At x=0.32, which is close to the critical composition of the FM-AF transition at room temperature, the uniaxial magnetocrystalline anisotropy (K_u) was about 1.7×10⁷ erg/cm³. A bit patterning process using the discontinuous FM-AF transition was studied. First, microfabricated FePt square films (1.7 nm thick) were prepared on the AF FePt_0.64Rh_0.36 film (6.7 nm thick). Second, those square films and the FePt_0.64Rh_0.36 film were mixed by annealing. The Fe and Pt atoms were thermally diffused into the FePt_0.64Rh_0.36 film locally, and the composition of the diffused areas changed to FM FePt_0.72Rh_0.28. A magnetic force microscopy study suggested that only the diffused areas changed from AF to FM phase. A minimum FM dot size of 300×300 nm² was realized, and the FM dots were multidomain structures. [ABSTRACT FROM AUTHOR]