A perpendicular magnetic tunnel junction (pMTJ) based on interfacial perpendicular magnetic anisotropy (PMA) CoFeB/MgO free layer is not only at the core of emerging magnetic memories but is also the key component of integrated spin logic devices thanks to its fast and reliable reading and low writing current. In domain-wall (DW) based spin logic devices, information is encoded and is carried by the position of a DW in the nanotrack shared by multiple MTJs. Thanks to its non-volatility, potentially low power and scalability, such devices are currently explored as an alternative path to circumvent the scaling limitations of CMOS.
Experimental results have shown that the use of a conventional pMTJs design for spin logic devices poses some challenges which are mainly related to the slow DW speed in CoFeB/MgO free layer and difficulties of fabricating such devices using industrial integration platforms. Recently, we have demonstrated a novel concept of pMTJ devices that incorporates the synthetic antiferromagnetic (i.e., two thin ferromagnetic layers separated by a non-magnetic layer in which the interaction between magnetic layers is antiferromagnetic) as magnetic free layer into the current pMTJ devices. This novel design is a key to advance for the spin logic devices thanks to the special properties of synthetic antiferromagnetic materials (robust against perturbation of external field, produce no stray fields, ultra-fast DW speed) compared to conventional ferromagnetic layer.
Key aspects of this PhD
To develop spin logic devices, imec uses a dedicated 300-mm wafer platform. The magnetic tunnel junction deposition and spin logic devices integration are carried out on an industry relevant 300 mm PVD cluster platform. The purpose of the PhD project is to pave the path towards integration of this novel pMTJ concept in a viable technological process for spin logic devices. This dissertation will focus on the understanding of the physical mechanism of DW transport in pMTJ with shared free layer by means of advanced electrical and physical characterization. This experimental work will be performed in close collaboration with micromagnetic modeling (OOMMF, Mumax) activities to support the experimental findings. This study will be finally focused on designing and investigating a fully functional spin logic devices, addressing both fundamental and technological challenges
An extensive toolset for structural, magnetic and electrical characterization is available including: XRR, XRD, VSM, Magneto-optical Kerr, current-in-plane tunneling, Hprobe electrical prober and a SOT electrical characterization setup.
Key to the Ph.D research is to
1) Study DW motion in magnetic materials with perpendicular magnetic anisotropy and their compatibility with pMTJ
2) Characterize magnetic and transport properties of novel pMTJ concept
3) Integrate novel pMTJ concept in fully functional spin logic devices
4) Study dynamics of DW propagation and demonstrated logic functionality in fully integrated devices
Required background: Master in Engineering Science, Master in Physics
Type of work: Literature study (10%), Experimental work (70%), Modelling (20%)
Supervisor: Kristiaan Temst
Daily advisor: Van Dai Nguyen, Sebastien Couet
The reference code for this position is 2020-052. Mention this reference code on your application form.
Chinese nationals who wish to apply for the CSC scholarship, should use the following code when applying for this topic: CSC2020-19.