Invvestigation of the electrical resistance in FeRh thin films for spintronics applications

Phase change thin films of FeRh have a lot of potential for technological applications such as antiferromagnetic spintronics [1], magnetocaloric devices [2], magnetic switches using an exchange-coupled composite [3], or in the field of heat assisted magnetic recording (HAMR) [4]. In particular, their main point of interest is their antiferromagnetic (AFM) to ferromagnetic (FM) metamagnetic phase transition. This transition gives in a significant change in electrical resistance which can be used in order to comprehend how the magnetic properties of the material change and their dependency on other parameters. This work is focused on the study of the variation of the electrical resistance of FeRh as a function of temperature and magnetic field. In order to calculate and fully understand the results of this electrical resistance as a function of temperature and magnetic field, the noise of the measurements and the thermal drift have to be taken into account. That is why the experiment will be divided into these two parts. First, the electrical measurements will be taken with the source meter unit (SMU), using the four-point method and later analyzed with the scientific data analysis package Origin. A LabVIEW program will be written as well to remotely control the devices. Then, fast temperature sweep rates, controlled by a previously designed PID (proportional integral derivative) controller [5], will be used in order to observe the thermal stability of the measurement system. The goal is to have a more stable PID controller so the temperature can be evenly incremented and reach the probe uniformly. Finally, these sweep rates will be taken at various applied magnetic field strengths and orientations in order to determine the resistance as a function of temperature. It is expected that these new results will provide physical insight into the nature of the thermodynamics of the AFM to FM phase transition. The setup needed for the experiments is based on a custom built variable temperature measurement cell made by Alex Eaton [5] connected to both Omega PID controller [6] and a Keithley 2400 source meter unit (SMU), which are connected to the heaters and the four-point probe respectively. Later, to minimize system noise, a Stanford Research Systems lock-in amplifier is used to detect the voltage, with a Keithley 6221 current source to provide the AC signal. To perform the respective operations previously mentioned, separate LabVIEW programs need to be fully designed and programmed. Also, a mobile and web application are created to monitor and help in the tracking of the experiments. Outgoing