epitaxial ultrathin films*

Ferrite material ReFeO₃, which is composed of rare earth elements (Re) and Fe generally has an orthorhombic structure in bulk form and show various electronic, magnetic properties. [1-3] One of the examples, ErFeO₃, which has strong spin-orbit coupling, has various magnetic phases i.e., Antiferromagnetic phase transition at T_N ~ 640 K, spin reorientation between 87-97 K, and long range ordering of Er³⁺ moment 4.5 K. This makes ErFeO₃ suitable testbed for magnetic modulation. Especially in an ultrathin scale, material has only a few numbers of out-of plane direction layers and it gives dimensional effect in addition to the strain effect. For instance, we can easily find significant effect of dimension on SrRuO₃ system. Electronic, magnetic phase transition and coupling between degrees of freedom is induced by dimensional effect. [5-7] We succefully fabricated ultrathin ErFeO3 film by using pulsed laser epitaxy to check the dimensional effect on magnetism. Magnetic structure of 2 nm ErFeO3 thin film in low temperature range is confirmed by polarized neutron reflectivity. As a result, this research on magnetic ultrathin film ErFeO₃ will enhance our understanding on generic magnetic property of low-dimensional oxide materials in the fundamental basis. Furthermore, it can contribute to research on magnetic insulator for spintronic devices. [8-13]