First-principles study of the easy-plane magnetocrystalline anisotropy in bulk hcp Co1−xIrx

Abstract

The soft magnetic material hcp CoIr has easy-plane magnetocrystalline anisotropy (MA) over a wide range of Ir content and has attracted interest from many researchers. This study presents a comprehensive investigation of the magnetization and MA of bulk hcp Co1−xIrx (0.03≤x≤0.25) alloys based on first-principles calculations. The results reveal that easy-plane MA is obtained for 0.06≤x<0.25, which agrees with the experimental results. The MA arises from the spin-orbit interactions of Co 3d orbitals. The Co1 atoms (the nearest neighbors of Ir atoms) and the Co2 atoms (the second nearest neighbors of Ir atoms) have different local environments; hence, the d orbitals split differently. Numerical calculations prove that the energy level alignment at the two sites plays an important role in determining the orientation of the local spin moments. The Co1 site preferentially adopts an in-plane local spin moment, while the Co2 site exhibits an out-of-plane local spin moment. The competition between the two sites determines the orientation of the easy axis of the hcp CoIr system. Our findings provide guidance for understanding and evaluating experimental studies on manipulating MA in disordered binary alloys.

Effect of seed layers on the static and dynamic magnetic properties of CoIr films with negative effective magnetocrystalline anisotropy

“…Apart from these, the different stacking structure ratios and crystallinity and atomic site ordering can also be linked drastically to K grain . [21] For the Ni seed layer film, amorphous regions appear as shown in Fig. 3.…”

“…According to the reported literature, [21,22] K grain is sensitive to the lattice geometry and microstructure, which is restricted by the growth mode of the magnetic layer. The growth modes are mainly governed by the seed-layer surfacefree energy γ s , the magnetic layer surface free energy γ f , the strain energy γ e , and the interface energy γ i .…”

Intermixing induced anisotropy variations in CoB-based chiral multilayer films

“…The greater extent of intermixing in the former may be attributed to the high surface mobility of Ir adatoms with larger sputtering power (Ir: 0.3 kW, Pt: 0.075 kW) [34,35]. We posit that the larger sputtering power-induced intermixing may result in enhanced Co-Ir alloying [34,36] [37,38]. Additionally, there are faint signs of a weak shoulder peak at ∼40.8 • attributed to slight Co-Pt fcc (111) formation.…”

Gyromagnetic ratio of oriented hcp Co1−x Ir x soft magnetic films

“…Soft magnetic films have attracted significant attention owing to their potential application to various high-frequency electromagnetic and spintronic devices, such as microwave absorbers, micro-transformers, recording media, magnetic memories, and spin valve devices [1][2][3][4][5]. Of the spin and magnetic properties that determine these practical applications, the gyromagnetic ratio (γ) is an important quantity, which corresponds to the Landé g factor (γ = g eµ0 2me , where m e is electron mass and µ 0 is the permeability of vacuum) [6,7].…”

“…Among the known soft magnetic films, close-packed hexagonal (hcp) CoIr films with grains that have a c-axis perpendicular to the film plane are a type of soft magnetic material with high easy-plane magnetocrystalline anisotropy energy that have been attracting special research interest. They are proven to be effective in increasing f r without decreasing the high initial permeability (µ i ) [22], in maintaining magnetic moments strictly lying in the film plane, as well as the Néel wall for thick films [5], and in achieving improved effects in recording medias [1,[23][24][25]. As an importance parameter, γ is involved in most of the reported works of CoIr films.…”