Atomic site preference, electronic structures, and magnetic properties of γ-brass type pseudo-binary Mn2Zn11–Ni2Zn11 at high Mn-contents

Abstract

Samples loaded as MnxNi2Zn11−x (x = 0.1–5) were synthesized using conventional high-temperature solid-state techniques and characterized using X-ray diffraction, neutron powder diffraction, and energy dispersive X-ray spectroscopy. A Hume-Rothery-type mechanism was applied, following the rigid band model, to rationalize the electronic stability of these phases. This shows that at low Mn substitution for Zn, there is a structural preference for Mn atoms to be farthest apart within the same cluster, but that with increasing Mn concentration, there is a favorability in maximizing shortest Mn–Mn contacts between adjacent clusters of the γ-brass-type structure. The properties involving temperature-dependent zero-field-cooled (ZFC) and field-cooled (FC) magnetization, susceptibility, M(H) hysteresis curves, thermoremanent magnetization, and memory effect were studied for Mn1.5Ni2Zn9.5. A spin glass state has been observed below the transition temperature of ∼58.5 K, which originates predominately from the disordered substitution of Mn for Zn atoms in the inner tetrahedral and octahedral shells of the structure.