We report on terahertz (THz) emission from a single layer ferromagnet which involves the generation of backflow nonthermal charge current from the ferromagnet/dielectric interface by femtosecond laser excitation and subsequent conversion of the charge current to a transverse transient charge current via the anomalous Hall effect (AHE), thereby generating the THz radiation. The THz emission can be either enhanced or suppressed, or even the polarity can be reversed by introducing a magnetization gradient in the thickness direction of the ferromagnet. The emission can also be enhanced using a synthetic antiferromagnet (SAF) via the same AHE mechanism. In addition, we demonstrate by both simulation and experiment that the THz emission provides a powerful tool to probe the magnetization reversal process of individual ferromagnetic layers in the SAF structure – an important building block for all types of spintronic devices.
Recently, spin-charge conversion induced magnetoresistance (MR) in a ferromagnet (FM) or its junction with a heavy metal (HM) has attracted great attention due to its potential applications in spintronics as well as being a powerful technique for studying spin-charge interaction and transport in magnetic thin films and heterostructures. In this talk, I will discuss our recent finding of an MR induced by the anomalous Hall effect (AHE) in a ferromagnet . When a charge current flows in a ferromagnet, both transverse charge and spin accumulations will occur at boundaries of the sample at steady state. The spin accumulation in turn induces a spin current either in an adjacent material or in the ferromagnet itself due to backflow of spin from the boundary. We demonstrate that the spin accumulation, subsequent spin backflow, and spin-charge conversion can give rise to a different type of spin current related magnetoresistance, dubbed as the anomalous Hall magnetoresistance (AHMR), which has the same angular dependence as the recently discovered spin Hall magnetoresistance (SMR). The AHMR is observed in four types of samples: co-sputtered (Fe1-xMnx)0.6Pt0.4, Fe1-xMnx/Pt multilayer, Fe1-xMnx with x = 0.17 – 0.65 and Fe, and analyzed using the drift-diffusion model. The AHMR provides an alternative route to study charge-spin conversion in ferromagnets and to exploit it for potential spintronic applications. In addition to AHMR, I will also discuss spin-torque induced by AHE in both single layer and multilayer structures and its applications in magnetization switching.