Study of the reproducibility window of optically induced quench-switching of antiferromagnetic CuMnAs films
Abstrakt
As the semiconductor industry is approaching its limitations, research is focusing more and more on novel approaches to keep the steady growth of computational power. One of these is the utilization of spin-based electronics in the research field of spintronics. Spintronics already proved itself in the realm of magnetic sensing with an effect of giant magnetoresistance, which enabled the modern hard drive. Most spintronic devices are based on ferromagnetic materials, which pose significant limitations on further miniaturization of components. Antiferromagnetic materials are ideal for spintronic applications as they exhibit no net macroscopic magnetization and thus emit no stray field, making them resilient to external magnetic fields while retaining internal magnetic order.
Antiferromagnets show some spintronic effects derived from their ferromagnetic counterparts, for example, anisotropic magnetoresistance or magnetic axis reorientation using current-induced spin-orbit torque. Other effects are unique to antiferromagnets, such as quench-switching. This effect is based on changes in the magnetic domain structure of the thin epitaxially grown films. These changes happen when the material is brought close to its Neél temperature by a current or an optical pulse and rapidly cooled. Even though the supplied heat had already been dissipated, due to the quench-switching effect, the material exhibits a resistivity change with a relaxation time of seconds at room temperature. Measured change in resistivity reaches tens of percent at room temperature and even a hundred percent at low temperature.
We focus on optically induced quench-switching, which utilizes a femtosecond laser pulse for excitation. Quench-switching signal increases with the energy density of supplied optical pulse with a distinct threshold. Due to the utilization of the Gaussian profile of the laser spot, only the small center region surpasses the quench-switching threshold at first. With increasing energy of the laser pulse larger area surpasses the threshold. The limiting factor is the permanent damage with the second energy density threshold, surpassed again in the center of the laser spot. This results in a defined window, where the quench-switching occurs without permanently damaging the film's surface. We will evaluate this window for different samples and explore some damage mitigation techniques. We will also show the chemical analysis of the damaged regions to show how the material changes after repeated optical pulsing