Influence of rare earth metal Ho on interfacial Dzyaloshinskii-Moriya interaction and spin torque efficiency in Pt/Co/Ho multilayers
Owing to the large spin-orbit coupling and tunable magnetization, heavy rare-earth metals Gd and Tb have great effects on the enhancement of spin-orbit torque (SOT) and fast domain wall (DW) motion. But the reports of heavy rare-earth metal Ho with more 4f electrons in the research of spintronics are limited. In this work, we found that the interfacial Dzyaloshinskii-Moriya interaction (DMI) and SOT in Pt/Co/Ho multilayers can be strongly influenced by changing the thickness of Ho (tHo) layer. At tHo = 2.4 nm, DMI exchange constant |D| and spin torque efficiency ξ_DL reach to the maximum values of 1.24 mJ/m2 and 0.137 respectively, which are comparable with that in other Pt/Co/nonmagnetic (NM) layer structures. The deterministic current-induced magnetization switching with low critical current density of 〖10〗^6 A/〖cm〗^2 can be realized when tHo is less than 5 nm. The Néel-type DW with left-handed chirality and positive sign D can be determined by observing the current-induced asymmetric DW motion. Our results are helpful to prompt the application of heavy rare-earth elements in the fields of DMI, SOT and chiral DW dynamics.