van der Waals Heterostructures*

To date, a few two-dimensional(2D) van der Waals(vdWs) ferromagnets have been studied showing potential for spintronic applications. A practical limiting factor has been the low curie temperature (T_c) of the used materials. Here we focus on bulk Fe₅GeTe₂ which was reported to have a T_c ~ 310K. In this work, we have studied the electrical transport and magnetic properties of Fe₅GeTe₂, as well as its potential for spin valve devices. Hall effect measurements indicate that its anomalous component is suppressed as the temperature is reduced with respect to the magneto-structural transition occurring at ~120 K or as the temperature is increased up to 300K. Meanwhile, the longitudinal magnetoresistance(MR) shows a maximum of ~ -12.5 % at 140 K. For the Fe₅GeTe₂/MoS₂/Fe₅GeTe₂ device, we observe a sizeable tunneling current when a thin MoS₂ crystal is chosen as the spacer. A sizeable change in magnetoresistivity as a function of the magnetic field is observed at low Ts, an indication for the spin valve mechanism. However, the effect is not yet observable at room T.

*This work is supported by the US-DoE through award DE-SC0002613.

*NHMFL is supported by NSF-DMR through 1644779 and the state of Florida.