[15p-PA01-1~58] 10 Spintronics and Magnetics (Poster)

[15p-PA01-45] Control of conductivity in cobalt-ferrite thin films with perpendicular magnetic anisotropy

〇Masaya Morishita¹, Tomoyuki Ichikawa¹, Masaaki Tanaka¹, Motoharu Furuta¹, Daisuke Mashimo¹, Syuta Honda², Jun Okabayashi³, Ko Mibu¹ (1.Nagoya Inst. Tech., 2.Kansai Univ., 3.U. Tokyo)

Keywords:cobalt ferrite, magnetic thin films, perpendicular magnetic anisotropy

We fabricated two types of Fe-rich cobalt-ferrite thin films, conductive Co_yFe_3-yO₄ (C-CFO) and insulative Co_xFe_3-xO_4+δ (I-CFO), with perpendicular magnetic anisotropy. Although the stoichiometric cobalt-ferrites are known as an insulating material, it is found that the conductivity in Fe-rich CFO can be controlled by changing the source materials and deposition conditions in the PLD technique. The C-CFO films also exhibit the PMA through the in-plane lattice distortion. We investigated the Fe-ions-specific valence states in C-CFO and I-CFO films by Mössbauer spectroscopy and XMCD, and found that the difference in conductivity corresponds to the abundance ratio of Fe²⁺ state at the octahedral (O_h) site. Furthermore, first-principles band-structure calculation suggested that the electronic structures of C-CFO are half-metallic characteristics and reproduced the difference in the DOS depending on the cation vacancies at the B-site in inverse spinel structures, which explains the difference in the conductivity between I-CFO and C-CFO. These add the novel functionalities in the oxide spintronics using Fe-rich CFO films.