Structure and Spin-Glass Magnetism of the Mn_xNi₂Zn_11–x Pseudobinary γ-Brasses at Low Mn Contents

Abstract

The pseudobinary Mn x Ni 2 Zn 11– x γ-brass-type phases at low Mn dopant levels ( x = 0.1–0.5) were investigated. Crystal structures were determined for the two loading compositions of x = 0.3 and 0.5. The structures were solved in the cubic space group of I 3 m and are described in close analogy to the Ni 2 Zn 11 parent γ-brass that is based on the 26-atom cluster, consisting of inner tetrahedron (IT), outer tetrahedron (OT), octahedron (OH), and cuboctahedron (CO). The refined site occupancies of the Mn x Ni 2 Zn 11– x ( x = 0.3, 0.5) reveal that the cluster center, which is empty in the Ni 2 Zn 11 , shows a partial occupation by Zn, with a partial depletion of Zn at the IT sites. The OH sites show a mixed Zn/Mn occupation. The OT and CO sites remain intact with respect to Ni 2 Zn 11 . Magnetic properties were studied for the Mn 0.3 Ni 2 Zn 10.7 composition. The temperature-dependent zero-field-cooled and field-cooled magnetization, the ac susceptibility, the M ( H ) hysteresis curves, the thermoremanent magnetization, and the memory effect demonstrate typical broken-ergodicity phenomena of a magnetically frustrated spin system below the spin freezing temperature T f ≈ 16 K. The Mn 0.3 Ni 2 Zn 10.7 γ-brass phase classifies as a spin glass, originating predominantly from the random distribution of diluted Mn moments on the octahedral partial structure.

Double Helix of Icosahedra Structure and Spin Glass Magnetism of the δ-Co2.5Zn17.5–xMnx (x = 0.4–3.5) Pseudo-Binary Alloys

“…The observed spin glass phase exhibits typical broken-ergodicity phenomena below the spin freezing temperature T f ≈ 8 K: (i) there is a large difference between the zfc and fc susceptibilities in low magnetic fields, (ii) the frequency-dependent spin freezing temperature T f (ν) depends logarithmically on the frequency ν of the applied ac magnetic field, (iii) the spin system shows remanence and hysteresis, (iv) the thermoremanent magnetization decays logarithmically slow in time, and (v) the memory effect was observed, where the nonergodic spin system memorizes its cooling history in zero magnetic field within the nonergodic phase. To this end, the investigated Co 2.5 Zn 17.1 Mn 0.4 alloy is similar to other nonergodic, magnetically frustrated systems like site-disordered canonical spin glasses, ,− ,, site-ordered but geometrically frustrated quasicrystals and their periodic approximants, ,, giant-unit-cell complex metallic alloys, high-entropy alloys, substitutionally disordered intermetallics and magnetic nanoparticles. , All of these systems exhibit a more or less identical dependence of the thermoremanent magnetization and the memory effect on the aging temperature T m , aging time t w , and cooling field H fc , where these out-of-equilibrium phenomena are theoretically still incompletely understood.…”

Ni1–xZnxFe2O4@CoO (x = 0.25 and 0.50) Nanoparticles for Magnetic Resonance Imaging

“…In Figure 1i(i), we have observed the planes (111), (002), (022), and (222) at 2θ values of 33, 42.7, 62, and 78.2°,respectively, corresponding to the cubic phase of cobalt oxide (CoO) in the shell with a space group of Fm3m (HighScore Plus reference code: 98-005-3057). Additionally, the planes (111), ( 022), ( 113), ( 222), ( 004), ( 133), ( 224), ( 115), ( 004), (135), and (026) at 2θ value of 18,30,35,37,43,47,53,57,62,66, and 71°ensure the development of Ni 0.75 Zn 0.25 Fe 2 O 4 in the core with cubic crystal phase having space group of Fd3̅ m with the reference code 98-016-3785. Hence, the formation of Ni 0.75 Zn 0.25 Fe 2 O 4 @CoO is confirmed in the case of system 1.…”

“…To further ensure the phase transition temperature, we perform a modified Curie–Weiss (CW) law fitting of inverse susceptibility with respect to temperature in the high thermal energy range ( T > 100 K), as shown in Figure c,f, following the expression: χ = χ 0 + C T − θ CW , where χ 0 represents a temperature-independent susceptibility term, C stands for Curie constant, and θ CW corresponds to CW temperature. χ 0 is the net susceptibility attributed to diamagnetic Larmor core susceptibility, the susceptibility of conduction electrons’ Pauli paramagnetic spin, and the presence of negative Landau susceptibility developed because of the orbital circulation of conduction electrons.…”

“…, 62 where χ 0 represents a temperature-independent susceptibility term, C stands for Curie constant, and θ CW corresponds to CW temperature. χ 0 is the net susceptibility attributed to diamagnetic Larmor core susceptibility, the susceptibility of conduction electrons' Pauli paramagnetic spin, and the presence of negative Landau susceptibility developed because of the orbital circulation of conduction electrons.…”