Magnetization and Anisotropy of Cobalt Ferrite Thin Films

Abstract

The magnetization of thin films of cobalt ferrite frequently falls far below the bulk value of 455 kAm-1, which corresponds to an inverse cation distribution in the spinel structure with a significant orbital moment of about 0.6 muB that is associated with the octahedrally-coordinated Co2+ ions. The orbital moment is responsible for the magnetostriction and magnetocrystalline anisotropy, and its sensitivity to imposed strain. We have systematically investigated the structure and magnetism of films produced by pulsed-laser deposition on different substrates (TiO2, MgO, MgAl2O4, SrTiO3, LSAT, LaAlO3) and as a function of temperature (500-700 C) and oxygen pressure (10-4 - 10 Pa). Magnetization at room-temperature ranges from 60 to 440 kAm-1, and uniaxial substrate-induced anisotropy ranges from +220 kJm-3 for films on deposited on MgO (100) to -2100 kJm-3 for films deposited on MgAl2O4 (100), where the room-temperature anisotropy field reaches 14 T. No rearrangement of high-spin Fe3+ and Co2+ cations on tetrahedral and octahedral sites can reduce the magnetization below the bulk value, but a switch from Fe3+ and Co2+ to Fe2+ and low-spin Co3+ on octahedral sites will reduce the low-temperature magnetization to 120 kAm-1, and a consequent reduction of Curie temperature can bring the room-temperature value to near zero. Possible reasons for the appearance of low-spin cobalt in the thin films are discussed. Keywords; Cobalt ferrite, thin films, pulsed-laser deposition, low-spin Co3+, strain engineering of magnetization.

References in corpus (8)

• Electronic structure of normal and inverse spinel ferrites from first principles
• Epitaxial strain effects in the spinel ferrites CoFe2O4 and NiFe2O4 from first principles
• First-principles calculation of magnetoelastic coefficients and magnetostriction in the spinel ferrites CoFe2O4 and NiFe2O4
• Effect of epitaxial strain on the cation distribution in spinel ferrites CoFe2O4 and NiFe2O4: a density functional theory study
• Strain-Induced Magnetic Anisotropy in Epitaxial Thin Films of the Spinel CoCr${}_2$O${}_4$
• A Robust Approach for the Growth of Epitaxial Spinel Ferrite Films
• Epitaxial Growth of Spinel Cobalt Ferrite Films on MgAl${}_2$O${}_4$ Substrates by Direct Liquid Injection Chemical Vapor Deposition
• Strain-magneto-optics of a magnetostrictive ferrimagnet CoFe2O4

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• Strain Engineering of Magnetic Anisotropy in Epitaxial Films of Cobalt Ferrite
• On the complexity of spinels: Magnetic, electronic, and polar ground states
• Materials Relevant to Realizing a Field-Effect Transistor based on Spin-Orbit Torques