Emergent magnetism in van der Waals materials offers exciting opportunities in fabricating atomically thin spintronic devices. One pertinent obstacle has been the low transition temperatures (T c) inherent to these materials, precluding room temperature applications. Here, we show that large structural gradients found in highly strained nanoscale wrinkles in Cr2Ge2Te6 (CGT) lead to significant increases of T c. Magnetic force microscopy was utilized in characterizing multiple strained CGT nanostructures leading to experimental evidence of elevated T c, depending on the strain percentage estimated from finite element analysis. Our findings are further supported by ab initio and DFT studies of the strained material, which indicates that strain directly augments the ferromagnetic coupling between Cr atoms in CGT, influenced by superexchange interaction; this provides strong insight into the mechanism of the enhanced magnetism and T c.

Solar cells made from Cu2ZnSn(S,Se)4 (CZTS)-derived materials have been widely studied for their favourable material properties utilized in photovoltaic energy conversion. Drawbacks of the materials are associated with low open...

Earth-abundant, environment-benign, cost-effective, and reliable renewable energy sources are urgently needed to meet the soaring global energy demands. Currently, solar cells based on chalcopyrite Cu(In,Ga)Se 2 (CIGSe) absorbers have yielded the highest power conversion efficiency (η) among all-inorganic thin-film technologies. [1] However, due to the scarcity of In and Ga in the Earth's crust, it would be difficult to satisfy the demands for terawatt (TW)-scale deployment using CIGSe-based cells. Kesterite Cu 2 ZnSnS 4 (CZTS), a derivative of CIGSe, is a promising candidate that satisfies all the aforementioned criteria for next-generation large-scale photovoltaic applications. However, the lower η of CZTS solar cells relative to CIGSe counterparts is still a major challenge for the development of kesterite solar cells. [2][3][4][5][6][7] The main bottleneck is the open-circuit voltage (V OC ) deficit (defined as E g /q À V OC , where E g and q respectively represent bandgap energy and the unit charge), primarily induced by large Shockley-Read-Hall (SRH) recombination at the CZTS/CdS heterointerface [8][9][10][11] and