Peierls-Like Distortion and High-Coercivity Cluster Glass in Lacunar CsCl-Related Phase: Co1.5Ni1.5Ga4

Abstract

This investigation focuses on the solid-state synthesis and a detailed structural and phase analytical investigation of the CoxNi3–xGa4 series along a constant Ga compositional line within Co–Ni–Ga phase space. Combined analysis of single crystal X-ray diffraction and neutron powder diffraction of CoxNi3–xGa4, x = 1.5 reveals a random distribution of Co and Ni over a single Wyckoff site, which contrasts with previous report suggesting atomic ordering. Phase analyses via X-ray powder diffraction indicates a vacancy order–disorder transition as the Co concentration increases beyond a critical limit. DFT calculation predicted a semimetallic and nonmagnetic ground state, supported by the absence of magnetic peaks or intensity enhancement at 10 K neutron data compared to 300 K. Interestingly, Peierls-like distortions are observed within the Ga substructure in the vacancy-ordered phase, whereas such distortions are absent in the vacancy-disordered phase. These distortions result in periodic charge localization and exhibit subtle alterations between room temperature and 180 K. Magnetic measurements further reveal cluster spin-glass behavior with a high coercivity. The nontrivial spin dynamics, coupled with large coercivity, makes this phase a compelling candidate for multifunctional applications.