Researcher(s)
- Aidan Wensel, Physics, Lafayette College
Faculty Mentor(s)
- John Xiao, Physics and Astronomy, University of Delaware
Abstract
RuO2 is a collinear antiferromagnet (AFM) of great recent interest to the field of spintronic memory, due to being metallic and having a Néel temperature greater than 300 K, as well as presenting exotic effects such as crystal spin-splitting torque. In contrast to ferromagnets (FMs), which have an easily measurable magnetization, the net-zero magnetization in AFMs presents a difficulty in probing the magnetic state, although the AFM state may be probed by exchange coupling effects in FM/AFM bilayers. In this work, the exchange coupling between NiFe/RuO2 bilayers was examined by temperature dependent vibrating sample magnetometry (VSM) up to 500 K for both the (101) and (110) orientations of RuO2. A strong coercivity enhancement and anisotropy were observed for NiFe/(101)RuO2 up to 500K and were found to decrease with temperature but persist unchanged after cooling. Thermal training was performed on NiFe/(110) RuO2 at 500 K and in +/- 2T cooling field, however no significant change in the exchange coupling was observed after accounting for remnant fields within the VSM. To determine the Néel temperature, a four-point DC probe station with a ceramic heating plate was used to measure the longitudinal resistivity of a RuO2 Hall Bar as a function of temperature up to 500 K, although no clear anomaly was observed in dρ/dT due to significant noise. Exchange coupling at high temperatures, as well as thermal training for Néel vector control in RuO2, are relevant for spintronics in order to exert control over the Néel state of the AFM, for memory device applications.