Abstract
Magnetic thin films showing high perpendicular magnetic anisotropy, Ku, and low saturation magnetization, Ms, are essential for realizing a small switching current in spintronic devices utilizing the current induced magnetization switching phenomena. The Cu2Sb-type MnAlGe intermetallic compound is a material showing uniaxial magnetocrystalline anisotropy with a relatively low Ms, which is attractive for spintronic application. In this study, the layer thickness dependence of Ku was investigated in poly-crystalline MnAlGe films, and the MgO template effect is discussed to achieve perpendicularly magnetized films in a few-nanometer thickness range. Experimental results suggested that the (001)-texture for the perpendicular magnetization was promoted by the MgO(001) template through the solid-phase epitaxy growth by annealing, which is similar with that in conventionally used CoFeB|MgO layered samples. Ku of about 2 × 106 erg/cm3 was achieved in a 5 nm-thick MnAlGe film using MgO buffer and capping exhibiting a low Ms value of approximately 200 emu/cm3 at room temperature. Although the magnitude of Ku is still in a moderate range, the low Ms is a promising feature for spintronic application.
Highlights
Magnetoresistive random access memories, MRAMs, are representative non-volatile memories which are expected to make electronic devices more energy-efficient and faster.1–3 Reduction of writing current for a memory bit is an important issue, for which the development of magnetization switching layer materials showing low saturation magnetization, Ms, is essential because of a proportional relationship between the writing current and Ms.4 In addition to the low Ms, high perpendicular magnetic anisotropy energy, Ku, is required to maintain the data retention of memory cells with a diameter of approaching a few nanometer size.2,3 As a material system for low-Ms and high-Ku, in this study, Mn-based intermetallic compounds showing Cu2Sb-type crystal structure are focused
The Cu2Sb-type MnAlGe intermetallic compound is a material showing uniaxial magnetocrystalline anisotropy with a relatively low Ms, which is attractive for spintronic application
Ku of about 2 × 106 erg/cm3 was achieved in a 5 nm-thick MnAlGe film using MgO buffer and capping exhibiting a low Ms value of approximately 200 emu/cm3 at room temperature
Summary
Magnetoresistive random access memories, MRAMs, are representative non-volatile memories which are expected to make electronic devices more energy-efficient and faster. Reduction of writing current for a memory bit is an important issue, for which the development of magnetization switching layer materials showing low saturation magnetization, Ms, is essential because of a proportional relationship between the writing current and Ms. In addition to the low Ms, high perpendicular magnetic anisotropy energy, Ku, is required to maintain the data retention of memory cells with a diameter of approaching a few nanometer size. As a material system for low-Ms and high-Ku, in this study, Mn-based intermetallic compounds showing Cu2Sb-type crystal structure are focused. As a material system for low-Ms and high-Ku, in this study, Mn-based intermetallic compounds showing Cu2Sb-type crystal structure are focused. Compared to conventionally used perpendicularly magnetized CoFeB films, the relatively low Ms and high Ku are attractive for MRAM applications; e.g., Ms ∼ 1000 emu/cm and Ku ∼ 2 × 106 erg/cm were reported for CoFeB films.. Compared to conventionally used perpendicularly magnetized CoFeB films, the relatively low Ms and high Ku are attractive for MRAM applications; e.g., Ms ∼ 1000 emu/cm and Ku ∼ 2 × 106 erg/cm were reported for CoFeB films.9 Another practical merit of the Cu2Sb-type Mncompounds is that the film samples showing perpendicular magnetization can be fabricated using single crystalline substrates, e.g., MgO (100), and glass or thermally oxidized silicon substrates.. To achieve high Ku in a small layer thickness region, the (001)-template effect of MgO buffer layer is discussed
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