Laser patterning of the room temperature van der Waals ferromagnet 1T-CrTe₂

Abstract

Lamellar crystalline materials, whose layers are bound 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 1T-CrTe2, we report a method for patterning lateral magnetic junctions. Exploiting the heat-induced phase transformation of the material into CrxTey 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 to protecting against oxidation, for which it is generally used), allowing the demonstration of room temperature ferromagnetism in <7 nm-thick 1T-CrTe2.

Lamellar crystalline materials, whose layers are bound 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 1T-CrTe2, we report a method for patterning lateral magnetic junctions. Exploiting the heat-induced phase transformation of the material into CrxTey 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 to protecting against oxidation, for which it is generally used), allowing the demonstration of room temperature ferromagnetism in <7 nm-thick 1T-CrTe2.