Large enhancement of magnetic damping in half-metallic Co₂MnSi Heusler alloy thin films with heavy metal Pt layer observed by the all-optical method

Manipulation of magnetic moments through spin transport is determined by the effective spin mixing conductance g _eff^↑↓ in the ferromagnetic metal/heavy metal heterostructure. Magnetization dynamics detection and evaluation of the Gilbert damping constant α is usually employed to estimate g _eff^↑↓. An all-optical pump-probe method is a powerful method for investigating α with high accuracy because an extrinsic contribution on α can be suppressed at a high precession frequency with an increasing external magnetic field. A large voltage signal was recently observed in half-metallic Heusler alloy Co₂MnSi thin film due to spin current injection; however, that voltage signal may also include contributions from thermal effect and spin Hall angle in the heavy metal layer. In this study, a large enhancement of α was observed in Co₂MnSi/Pt heterostructure by using the all-optical method. g _eff^↑↓ for Co₂MnSi/Pt was 2 times larger than that for Fe/Pt. This large g _eff^↑↓ is promising for spintronic device applications.