Epitaxial nanomagnets with intrinsic uniaxial in-plane magnetic anisotropy

High quality epitaxial Fe films were grown on GaAs(001) by molecular beam e pitaxy and magnetron sputtering. Two-dimensional arrays of circular dots wi th 200 nm diameter and 500 nm period were made by interferometric lithograp hy and ion beam etching. Large area patterning (about 1 cm(2)) allows integ ral magnetic measurements with an alternating gradient magnetometer. The ma gnetic behavior of thick patterned films is dominated by the demagnetizing field. Ultrathin continuous films and dot arrays of these show a strong uni axial in-plane magnetic anisotropy with the easy axis in [110] direction wh ich is fully conserved during the patterning process. This means that two s table remanent single domain states exist in ultrathin Fe(001) sub-mu m dot s on GaAs(001) because (i) the magnetostatic energy is not important due to the small aspect ratio, and (ii) the Fe/GaAs(001) interface creates a stro ng uniaxial in-plane magnetic anisotropy. Nanomagnets with these properties seem very attractive for high density memory elements. (C) 2000 American I nstitute of Physics. [S0021- 8979(00)47508-0].