Transition from ferro- to ferrimagnetic ordering via Mn-disorder in (Ni,Co)MnGa quaternary Heusler alloy
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An inclusive investigation of electronic and magnetic properties of ordered and disordered (Ni,Co)MnGa quaternary Heusler alloy has been undertaken using the density functional theory-based full potential linearized augmented plane wave method within generalized gradient approximation as exchange–correlation potentials. We observe that the increasing Mn concentration in Ni1−x CoMn1+x Ga (x = 0, 0.25, 0.50 and 0.75) lowers the ferromagnetic (FM) character of the parent (Ni,Co)MnGa alloy. This change creates two inequivalent Mn sites aligning antiparallel to each other and generates the ferrimagnetic (FiM) ordering in all resultant disordered alloys. Further, this replacement sets off a structural change from Y- to Xa-structure. The highest magnetic moment has been found to be 4.95 μB for ordered (Ni,Co)MnGa alloy, whereas it decreases with increase in Mn-concentration for disordered systems. The variation of half-metallicity with increasing Mn concentration is analysed. The stability of FM and FiM state for the present ordered and disordered alloys, respectively, is also examined.
KeywordsSpin Polarization Total Magnetic Moment Transition Metal Atom Spin Channel Atomic Magnetic Moment
The computation in this study was performed on the Kalki server at the Inter University Accelerator Centre (IUAC), New Delhi, India. The authors, M. K. Kashyap and M. Singh, gratefully acknowledge the support from the University Grant Commission (UGC), New Delhi, INDIA for providing the research facilities under the scheme SAP-I for faculty members and financial assistance through the SRF (RGNFS), respectively.