Defect engineering of magnetic ground state in EuTiO₃ epitaxial thin films

Abstract

Atomistic defect engineering through the pulsed laser epitaxy of perovskite transition metal oxides offers facile control of their emergent opto‐electromagnetic and energy properties. Among the various perovskite oxides, EuTiO3 exhibits a strong coupling between the lattice, electronic, and magnetic degrees of freedom, which is highly susceptible to atomistic defects. In this study, we investigated the magnetic phase of EuTiO3 epitaxial thin films via systematic defect engineering. A magnetic phase transition from an antiferromagnet to a ferromagnet was observed when the unit cell volume of EuTiO3 expanded due to the introduction of Eu–O vacancies. Optical spectroscopy and density functional theory calculations show that the change in the electronic structure as the ferromagnetic phase emerges can be attributed to the weakened Eu–Ti–Eu super‐exchange interaction and the introduction of the ferromagnetic Eu–O–Eu interaction. Facile defect engineering in EuTiO3 thin films facilitates understanding and tailoring of their magnetic ground state.

Tunable Ferromagnetism in LaCoO3 Epitaxial Thin Films

“…[9][10][11][12] Iron yttrium garnet (YIG), α-Fe 2 O 3 , spinel CoFe 2 O 4 , EuS, EuO, and strained EuTiO 3 thin films are some examples of FM-I materials. [13][14][15][16][17][18][19] Epitaxially strained LaCoO 3 (LCO), e.g., deposited on SrTiO 3 (STO), (LaAlO 3 ) 0.3 (Sr 2 AlTaO 8 ) 0.7 (LSAT), or YAlO 3 substrates, is an emerging FM-I with a Curie temperature above the liquid N 2 temperature (T C ≈ 80 K). [20,21] Long-range FM ordering in epitaxial LCO thin films is facilitated by straininduced lattice distortions.…”

Mechanisms for point defect-induced functionality in complex perovskite oxides

“…Oxygen vacancies can also be used to alter an existing magnetic order. In EuTiO 3 , the creation of Eu and O vacancy pairs alters the geometry and results in a weakening of the antiferromagnetic Eu-Ti-Eu interactions while introducing ferromagnetic Eu-O-Eu exchange, leading to a transition from antiferromagnetism to ferromagnetism [59]. Spinpolarized Ti 3+ sites were invoked for an antiferromagnetic to ferromagnetic transition in oxygen-deficient EuBaTi 2 O 6 , where the antiferromagnetic Eu 2+ -Eu 2+ exchange in the stoichiometric material is dominated by ferromagnetic Eu 2+ -Ti 3+ -Eu 2+ exchange in presence of oxygen vacancies [60].…”

Ferromagnetic insulating substrate for magnetic proximity studies: LaCoO3 thin film

“…However, ferromagnetism generally accompanies metallicity [11] and thus, finding a suitable FMI candidate remains a challenging task. Nevertheless, there are few FMIs including EuX (X = O, S) [12,13], La 0.7 Sr 0.3 MnO 3 thin film [14,15], and EuTiO 3 thin film [16][17][18]. Additionally, tensile-strained LaCoO 3 (LCO) has recently been identified to be a ferromagnet, which can also provide opportunities as an FMI substrate [19][20][21][22][23][24], with possible integration with various perovskite ultrathin films.…”