ELECTRONIC MATERIALS Coexistence of superconductivity and ferromagnetism in defect-induced NbSe 2 single crystals Rukshana Pervin 1 , Manikandan Krishnan 2 , Arumugam Sonachalam 2 , and Parasharam M. Shirage 1, * 1 Discipline of Metallurgy Engineering and Materials Science, Indian Institute of Technology Indore, Simrol, Indore 453552, India 2 Centre of High Pressure Research, School of Physics, Bharathidasan University, Tiruchirappalli 620024, India Received: 23 November 2018 Accepted: 4 June 2019 Ó Springer Science+Business Media, LLC, part of Springer Nature 2019 ABSTRACT Here, we report the coexistence of superconductivity (SC) and ferromagnetism (FM), which are considered as two exclusive phenomena. We have grown NbSe 2 single crystals by chemical vapor transport method. In NbSe 2 , we have intentionally created Se deficiency (i.e., NbSe 1.85 ) by substitution of Fe atoms (i.e., Fe 0.0015 NbSe- 2 ). The temperature-dependent resistance measurements confirm that both Se and Fe defects decrease the superconducting transition temperature (T c ) due to the presence of disorder as well as enhancement of scattering phe- nomena of charge carriers. Subsequently, the temperature-dependent magneti- zation measurement gives the signature of coexistence of SC and FM in NbSe 1.85 . Interestingly, there is no such evidence in case of Fe 0.0015 NbSe 2 . The T c and T FM are estimated from the derivative plot of DC susceptibility curves. It reveals that the bulk SC with FM in NbSe 1.85 is obtained up to 0.05 T. Further, the M–H plot confirms the coexistence of SC and FM in NbSe 1.85 at 2 K. In addition, the upper limit of superconductivity at different temperatures for NbSe 1.85 and Fe 0.0015 NbSe 2 is calculated which reflects the superposition region of SC and FM in NbSe 1.85 and the suppression of the SC in Fe 0.0015 NbSe 2 as compared to NbSe 2 . 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. Introduction The interaction between two prominent phenomena superconductivity (SC) and ferromagnetism (FM) has been attracting scientific interest for a long time in the field of superconducting spintronic and quantum computing [1–4]. Superconductivity is a phenomenon with exactly zero DC electrical resistance, and the expulsion of magnetic flux lines occurs due to the formation of singlet Cooper pair electrons [5]. Meanwhile, FM diminishes this singlet s-wave pair- ing and thus contradicts the coexistence of FM and SC [6, 7]. However, the coexistence of these two phenomena was evinced in 1970s by investigating the Address correspondence to E-mail: pmshirage@iiti.ac.in; paras.shirage@gmail.com https://doi.org/10.1007/s10853-019-03757-5 J Mater Sci Electronic materials