Quantum-well-induced engineering of magnetocrystalline anisotropy in ferromagnetic films

Abstract

Tuning quantum well states (QWSs) to govern physical properties in nanoscale leads to the development of advanced electronic devices. Here, we propose that QWSs can be engineered to control magnetocrystalline anisotropy energy (MCAE) which dominates the magnetization orientation (that is, the easy axis) of a ferromagnetic thin film. We investigate from first-principles the MCAE of the bcc Fe film on an Ag substrate. The calculated MCAE oscillates largely as Fe thickness increases agreeing well with experiments, and reaches oscillation extremes as the Fe d-orbital QWSs approach the Fermi level (E F ). Crucially, we find that this phenomenon stems from the combined effect of intrinsic spin-orbit interaction (SOI) and Rashba SOI field on the Fe QWSs, which modulates the density of states at E F as the Fe thickness varies. Moreover, this effect offers a way to tune not only the strength of magnetic anisotropy but also the easy axis of a Fe film by shifting E F within ten meV via moderately charge injection, which could realize advanced memory devices with ultra-low power consumption.

First-principles investigation of magnetocrystalline anisotropy oscillations in Co2FeAl/Ta heterostructures

“…39 Recent first-principles studies have correlated QWS with MCAE in Ag/Fe and IEC in Fe/Ag/Fe structures. 40,41 These works indicate that the influence of QWS on magnetic properties, specifically MAE, may become salient in some structures.…”

First-Principles Calculations Predict Tunable Large Magnetic Anisotropy Due to Spin-Polarized Quantum-Well Resonances in Nanometer-Thick SrRuO3 Films: Implications for Spintronic Devices

“…The spin-polarized quantum well states (QWSs) are confirmed to significantly contribute to the MCAE. − Different spins and groups of the QWSs, ,, surface states, , and intrinsic and interfacial spin–orbital interactions − are found to cooperate to induce the MCAE. Moreover, the positive or negative sign of the QWSs-induced MCAE directly decides whether the direction of the easy axis is out of plane and in plane, respectively. , Crucially, the spin-polarized d xz and d yz QWSs have been observed in SRO(001) ultrathin films recently . Investigation of the MCAE due to the QWSs opens routes to study the nature of the magnetocrystalline anisotropy and also how to tune it.…”

Correlation of interfacial perpendicular magnetic anisotropy and interlayer exchange coupling in CoFe/W/CoFe structures

“…Moreover, by replacing Ta with Hf [7], Mo [8], and W [9] etc, PMA can be further enhanced. The origin of magnetic anisotropy energy (MAE) in the MgO/CoFe/HM structures were researched by firstprinciples calculations and attributed to both the MgO/CoFe interface and the CoFe/HM interface [10][11][12].…”