Disorder-mediated quenching of magnetization in NbVTiAl: Theory and experiment

• Published in: Journal of magnetism and magnetic materials Vol. 551; p. 169124
• Main Authors: Rani, Deepika, Kangsabanik, Jiban, Suresh, K.G., Alam, Aftab
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.06.2022; Elsevier BV
• Subjects: Alloys; Curie temperature; Density functional theory; Ferrimagnetism; Fully compensated ferrimagnetism; Half-metals; Heusler alloys; Magnetic moments; Magnetic properties; Magnetism; Magnetization; Polarization (spin alignment); Quaternary alloys; Spin polarization; Temperature dependence; Transport properties; X-ray diffraction; Transport properties; Heusler alloys; Spin polarization; Density functional theory; Magnetism; Fully compensated ferrimagnetism; Half-metals
• ISSN: 0304-8853; 1873-4766
• DOI: 10.1016/j.jmmm.2022.169124

In this paper, we present the structural, electronic, magnetic and transport properties of a equiatomic quaternary alloy NbVTiAl. The absence of (111) and (200) peaks in X-ray diffraction (XRD) data confirms the A2-type structure. Magnetization measurements indicate a high Curie temperature and a negligibly small magnetic moment (∼10−3 μB/f.u.) These observations are indicative of fully compensated ferrimagnetism in the alloy. Temperature dependent resistivity indicate metallic nature. Ab-initio calculation of fully ordered NbVTiAl structure confirms a nearly half metallic behavior with a high spin polarization (∼90 %) and a net magnetic moment of 0.8 μB/f.u. (in complete contrast to the experimental observation). One of the main objective of the present paper is to resolve and explain the long-standing discrepancy between theoretical prediction and experimental observation of magnetization for V-based quaternary Heusler alloys, in general. To gain an in-depth understanding, we modeled various disordered states and its subsequent effect on the magnetic and electronic properties. The discrepancy is attributed to the A2 disorder present in the system, as confirmed by our XRD data. The presence of disorder also causes the emergence of finite states at the Fermi level, which impacts the spin polarization of the system. •We report a combined theoretical and experimental investigation of NbVTiAl alloy.•The alloy crystallizes in A2-type structure and has a net magnetization of ∼10-3μB/f.u.•Ab-initio calculation of fully ordered NbVTiAl structure confirms a nearly half metallic behavior and a net magnetic moment of 0.8 μB/f.u.•The discrepancy in magnetization is attributed to the A2 disorder.•Disorder plays a decisive role in controlling the magnetic/electronic properties of NbVTiAl.