Epitaxial RECo5 single layer and bilayer films

Intermetallic RECo phases are widely used in permanent magnet applications due to their large magnetocrystalline anisotropy. Therefore in previous work we developed epitaxial growth of thin SmCo5 and PrCo7 films on Cr buffered MgO(110) substrates with high coercivity or energy density. RECo5 phases with RE=Pr or Nd are also known to exhibit spin reorientation transition from an uniaxial state into easy-cone or easy-plane arrangement and are thus interesting from a fundamental point of view. In this work we present the temperature and field dependent magnetic behaviour of epitaxial NdCo5, SmCo5 and PrCo5 single layer films and bilayers. Epitaxial NdCo5 films grow with the same single orientation of the c-axis established for SmCo5 and exhibit an easy-axis to easy-plane transition. Bilayers of PrCo5 and SmCo5 likewise grow epitaxially with one common orientation of the c-axis throughout the layer stack. Despite their largely different coercivity when grown as single layers the bilayer films reverse magnetization in one large irreversible step indicating a strong interlayer exchange coupling.