The field of spintronics, which integrates the charge and spin properties of electrons to develop electronic devices with enhanced functionality and energy efficiency, has expanded into new applications. Beyond current technologies such as hard disk drive read heads and magnetic random-access memory (MRAM), researchers are now investigating flexible spintronics for use in wearable devices and sheet-type sensors. For these applications, detecting small changes in mechanical stress through electrical resistance modulation is essential. This requires not only materials with significant magnetoresistance effects but also control over their magnetoelastic properties.
A research team systematically studied the magnetoelastic properties of Fe4N and its substituted variants, Fe4-xMnxN and Fe4-yCoyN. These materials, composed of widely available elements, were examined for their potential in flexible spintronics. High-quality single-crystal nitride films were fabricated on strontium titanate (001) substrates, and measurements of magnetic strain in the [100] direction revealed a negative magnetostriction of -121 ppm in Fe4N. This value is of the same order as Fe-Ga alloys, which are known for their magnetostriction properties. Additionally, by varying the cobalt content in Fe4-yCoyN, the team observed a positive magnetostriction of +46 ppm in Fe2.3Co1.7N, indicating that the magnetoelastic property can be effectively modulated through elemental substitution.
To understand the mechanism behind this tunability, the researchers analyzed the relationship between magnetoelastic properties and other magnetic characteristics, such as saturation magnetization, magnetic anisotropy, and magnetic damping. The study found a strong correlation between magnetic damping and magnetoelastic behavior. Further comparison with first-principles calculations suggested that the density of states at the Fermi level for d-electrons plays a key role in determining both properties. This insight provides a pathway for further refinement of magnetoelastic properties, potentially leading to improved material performance for flexible spintronics applications.
Keita Ito, an assistant professor at the Institute for Materials Research (IMR) at Tohoku University, says, "By demonstrating that iron nitride materials exhibit both spintronic and magnetoelastic properties, we provide a new perspective on material selection for flexible spintronics devices. Understanding how several magnetic properties are interrelated may enable the design of highly responsive strain sensors in the future."
Moving forward, the research team aims to fabricate magnetoresistance devices using ferromagnetic nitride films on flexible substrates. This will allow them to test the effectiveness of these materials in detecting mechanical stress with high sensitivity. Since iron nitride-based materials are composed of elements with minimal environmental impact and are not subject to resource scarcity, they offer a promising direction for the development of low-cost, large-area flexible sensor technologies.
- Publication Details:
Title: Giant tunability of magnetoelasticity in Fe4N system as a platform to unveil correlation between magnetostriction and magnetic damping
Authors: Keita Ito, Ivan Kurniawan, Yusuke Shimada, Yoshio Miura, Yasushi Endo, and Takeshi Seki
Journal: Communications Materials
