ASCENT Theme 2 Liaison Meeting / Manipulation of VCMA through tunable work function underlayers and its integration with SOT

Time: Thu Oct 22, 2020, 4:00 pm - 5:00 pm

Location: webex

Time: 4:00 pm - 5:00 pm eastern

Title: Manipulation of VCMA through tunable work function underlayers and its integration with SOT

Presenter: Thomas Peterson and Jian-Ping Wang, University of Minnesota 

Abstract:  Theoretical calculations have predicted a pJ/Vm and bidirectional VCMA effect in Fe/MgO interfaces with highly hole-doped electron concentrations. The calculated bidirectional VCMA occurs at electric field values of 2 V/nm much higher than possible in traditional gating devices. To reach these extreme electric fields, we have proposed inserting high work function materials under the magnetic layer which will deplete the magnetic layer shifting the centroid of our gating window into the hole-doped regime. We have demonstrated control of the underlayer’s work function by utilizing Ta(0.5nm)/Pd(x)/Ta(1nm) trilayers. By modulating the Pd thickness from 0-20 nm we have observed a tunable change in the Ta layer’s work function from 4.3eV to 4.8eV. Our early results using a Ta(0.5nm)/Pd(2nm)/Ta(1nm)/CoFeB(1.2nm)/MgO(42nm) stack structure demonstrated a linear VCMA coefficient of -108 fJ/Vm. While the effect we see is still linear we see an improvement of ~3x from the commonly reported VMCA coefficient for Ta/CFB/MgO structures. We are working to develop new stacks replacing Pd for Pt to demonstrate the tunable VCMA effect integrated with SOT switching.

 

This meeting is only available to the JUMP research community, such as Principal Investigators, Postdoc researchers, Students, and Industry/Government liaisons.