Coexistence of superconductivity and ferromagnetism in defect-induced NbSe2 single crystals

Here, we report the coexistence of superconductivity (SC) and ferromagnetism (FM), which are considered as two exclusive phenomena. We have grown NbSe2 single crystals by chemical vapor transport method. In NbSe2, we have intentionally created Se deficiency (i.e., NbSe1.85) by substitution of Fe atoms (i.e., Fe0.0015NbSe-2). The temperature-dependent resistance measurements confirm that both Se and Fe defects decrease the superconducting transition temperature (Tc) due to the presence of disorder as well as enhancement of scattering phenomena of charge carriers. Subsequently, the temperature-dependent magnetization measurement gives the signature of coexistence of SC and FM in NbSe1.85. Interestingly, there is no such evidence in case of Fe0.0015NbSe2. The Tc and TFM are estimated from the derivative plot of DC susceptibility curves. It reveals that the bulk SC with FM in NbSe1.85 is obtained up to 0.05 T. Further, the M–H plot confirms the coexistence of SC and FM in NbSe1.85 at 2 K. In addition, the upper limit of superconductivity at different temperatures for NbSe1.85 and Fe0.0015NbSe2 is calculated which reflects the superposition region of SC and FM in NbSe1.85 and the suppression of the SC in Fe0.0015NbSe2 as compared to NbSe2. This study not only provides the role of defects in SC and FM properties but also encourages to study the effect of defects on other types of superconducting materials.