Uncovering the origin of magnetic moment enhancement in Fe-Co-Ir alloys via high-throughput XMCD

Abstract

High-magnetization ferromagnets play a crucial role in advancing spintronics, magnetic sensing, and high-density data storage technologies. Fe-Co-Ir alloys, previously identified through machine learning to potentially surpass the Slater-Pauling limits for transition-metal magnets, present a valuable platform for uncovering the mechanisms behind their enhanced magnetic properties. This study investigates the influence of Ir doping on the element-specific magnetic moments by high-throughput x-ray magnetic circular dichroism (XMCD) techniques using both soft and hard x-rays on Fe-Co-Ir single-crystal composition-spread thin films. A single-crystal composition-spread thin film of (Fe75Co25)100-xIrx (x=0-11 at%) was fabricated on a MgO(100) substrate using a combinatorial sputtering technique, enabling a systematic analysis of compositional variations. XMCD measurements revealed that Ir doping enhances the magnetic moments of Fe, Co, and Ir, with a particular emphasis on the orbital contribution of Fe and Ir. These experimental findings are supported by ab initio calculations, which highlight increased electron localization and stronger spin-orbit coupling between Ir 5d electrons and Fe/Co 3d electrons as the primary mechanisms behind the enhanced magnetization. This study provides a deeper understanding of the electronic and magnetic moments in Fe-Co-Ir alloys, offering valuable insights for the development of next-generation ferromagnetic materials optimized for advanced technological applications.