Advances in Magnetics Co–Fe Metal/Native-Oxide Multilayers: A New Direction in Soft Magnetic Thin Film Design II. Microscopic Characteristics and Interactions

metal/native-oxide multilayer (MNOM) films exhibit soft magnetic properties, large magnetization, high resistivity, and a potential operating bandwidth of several gigahertz. These attractive characteristics are facilitated by ultrathin magnetic native oxide layers introduced to provide a high-resistivity barrier between nanocrystalline metal layers while preserving interlayer coupling and contributing to the net moment. This paper addresses several important features of the MNOM system from a microscopic perspective. The uniaxial anisotropy of MNOM thin films is discussed in detail and “exchange averaging ” is invoked to account for its vanishingly small effective dispersion. The role of the native oxide in establishing interlayer exchange coupling is demonstrated, and a detailed ac-count of the nature of the oxide is presented. In the Fe MNOM system, the oxide is shown to have a volume-averaged magnetization of 732(35) emu/cm3, with a temperature dependence comparable to that of metallic Fe. The magnetism of this largely “interfacial ” oxide is supported by the metal and collapses in the absence of the metal. The oxide retains a large net moment for Co fractions up to at least = 50, but oxide magnetism is lost at high Co fractions, coinciding with the loss of soft magnetic properties