UC San Diego

The rare earth iron garnets (REIG) are a technologically important class of materials owing to their ferrimagnetism, low spin damping, large band gaps, high Curie points and chemical stability. Epitaxial REIG films are also capable of producing perpendicular magnetic anisotropy (PMA) which results from the interfacial strain due to lattice mismatch between film and substrate, and causes the easy axis of magnetization to point out-of-plane of the film. This unique set of properties makes REIGs attractive for spintronics device research in addition to fundamental spin transport studies. One obstacle that researchers face is that high-quality targets are not commercially available for many REIG compositions. Our work demonstrates a method of producing dense, fine structured REIG targets via wet chemical synthesis routes and subsequent consolidation of REIG powders using the current-activated, pressure-assisted densification technique. So far, PMA has been successfully tuned in REIG films by means of controlling the substrate material, substrate orientation, film thickness, and to a lesser extent by chemical substitution. Our method can easily produce chemically substituted REIG targets because we synthesize our own powders, which we demonstrated by the synthesis of a full compositional range of Y3(1-X)Tm3XFe5O12 solid solution powders. The lattice parameter and magnetic saturation of the Y3(1-X)Tm3XFe5O12 powders varied with composition, enabling further control over growth induced PMA. Most REIG films with PMA grown for research are produced using pulsed laser deposition (PLD), however, our work demonstrates that off-axis RF sputtering can also produce films with PMA. Sputtering is important for the large-scale manufacture of these films because it is more widely used in industry and has the added benefit of producing larger area films than PLD. Specifically, we grew epitaxial europium iron garnet (EuIG) films with robust PMA at a maximum thickness of 102 nm, the thickest EuIG films with PMA to date. Through the use of asymmetric reciprocal space mapping, we additionally showed that the lattice parameter and elastic properties of EuIG films grown by sputtering or PLD can deviate substantially from the literature values, which is likely explained through a combination of stoichiometric deviation and atomic point defects.