Laser patterning of the room temperature van der Waals ferromagnet 1$T$-CrTe$_2$

TL;DR

This paper presents a laser-based patterning technique for creating lateral magnetic junctions in the room temperature ferromagnet 1T-CrTe2, enabling control over magnetic properties at the micron scale.

Contribution

It introduces a novel laser patterning method exploiting phase transformations in 1T-CrTe2, with substrate and encapsulation strategies to optimize magnetic patterning and stability.

Findings

Laser heating induces phase transformation for patterning

Substrate type influences phase transformation control

h-BN encapsulation preserves ferromagnetism in thin layers

Abstract

Lamellar crystalline materials, whose layers are bond by van der Waals forces, can be stacked to form ultrathin artificial heterostructures, and in particular vertical magnetic junctions when some of the stacked materials are (ferro)magnetic. Here, using the room temperature van der Waals ferromagnet 1$T$-CrTe$_2$, we report a method for patterning lateral magnetic junctions. Exploiting the heat-induced phase transformation of the material into Cr$_x$Te$_y$ compounds ($x/y>1/2$), we use local laser heating to imprint patterns at the micron-scale. Optimizing laser heat dissipation, we further demonstrate the crucial role of the substrate to control the phase transformation. If plain, unstructured poorly heat-conducting substrates allow for direct writing of magnetic patterns, structured $h$-BN layers can serve as heat stencils to draw potentially thinner patterns. Besides, $h$-BN encapsulation turns out to be heat-protective (in addition from protecting against oxidation as it is generally used for), allowing the demonstration of room temperature ferromagnetism in $<$7~nm-thick 1$T$-CrTe$_2$.