Magnetic properties of epitaxial Fe/MgO structures on Si(100)

•An MBE growth of Fe/MgO on a Si(100) substrate.•Observation of a clear four-fold magnetic anisotropy in the film plane.•Determination of the first-order cubic magnetocrystalline anisotropy.

The magnetic properties of epitaxial Fe/MgO structures on Si(100) substrates are investigated over an Fe thickness range of 2–20 nm. Superparamagnetic behavior is observed at an Fe thickness of 2 nm, indicating that no continuous Fe thin film is formed. At Fe thicknesses of 5 nm and higher, a continuous two-dimensional layered structure is formed, which has a dominant epitaxial relationship of Fe[010](100)//MgO[011¯] (100)//Si[011¯](100) and a minor portion of Fe[010](100)//MgO[010](100)//Si[011¯](100). This structural feature is echoed by a four-fold magnetic anisotropy in the film plane, and this tendency increases with increasing Fe thickness. The strength of the first-order cubic magnetocrystalline anisotropy, which can only be extracted from the structures, is in the range of 3.87×105–4.04×105 erg/cm3, weaker than that of bulk Fe (4.8×105 erg/cm3).