Effects of coexisting spin disorder and antiferromagnetism on the magnetic behavior of nanostructured (Fe79Mn21)1−xCux alloys

Abstract

We report a magnetic study on nanostructured (Fe79Mn21)1−xCux (0.00 ≤ x ≤ 0.30) alloys using static magnetic measurements. The alloys are mainly composed by an antiferromagnetic fcc phase and a disordered region that displays a spin-glass-like behavior. The interplay between the antiferromagnetic and magnetically disordered phases establishes an exchange anisotropy that gives rise to a loop shift at temperatures below the freezing temperature of moments belonging to the disordered region. The loop shift is more noticeable as the Cu content increases, which also enhances the spin-glass-like features. Further, in the x = 0.30 alloy the alignment imposed by applied magnetic fields higher than 4 kOe prevail over the configuration determined by the frustration mechanism that characterizes the spin glass-like phase.

Bi-Magnetic Iron(III) Oxide Nanocrystals Embedded in MCM-41 Mesoporous Silica

“…Hysteresis loops were also recorded at different temperatures after field cooling the sample from room temperature under a cooling field H FCool = 50 kOe (Figure a). A loop shift reflects the existence of an exchange anisotropy due to the coexistence of ferromagnetic (FM or FiM) and AF phases, disordered/AF, or disordered/FM phases with interfacial interactions. , In our case, we observe a shift to negative fields when the loops were measured below 20 K, i.e., once the blocking/freezing of moments has taken place. The exchange bias field ( H EB ), defined as H EB = (| H CR | – | H CL |)/2, where H CR and H CL are the right and left coercive fields, respectively, measured at different temperatures is shown in Figure b.…”

“…A loop shift reflects the existence of an exchange anisotropy due to the coexistence of ferromagnetic (FM or FiM) and AF phases, disordered/AF, or disordered/FM phases with interfacial interactions. 35,36 In Figure 8 shows the results of the AC-susceptibility measurements. The in-phase susceptibility component, χ′, shows a maximum at a temperature T max (T max ∼ 22 K for a frequency f = 48 Hz) that coincides with the occurrence of the turning point of the out-of-phase component, χ″.…”

“…Similar behaviors have been observed in nanosystems with interfacial exchange coupling between coexisting magnetic phases. 36,40 This has been interpreted as the existence of energy competition among the exchange interactions among the spins located at the interfaces and the Zeeman energy established by H FCool . In our case, as H FCool increases up to 5 kOe, the exchange anisotropy dominates below T B , and the loops are shifted.…”

Short-range structural and magnetic order in rapidly-solidified Ag Mn alloys

“…1,10,11 Among metallic AF materials, manganese-based binary systems such as Fe-Mn, 12 Ir-Mn 13 and Cu-Mn 14 hold potential as components in exchange-biased magnets because their magnetic properties may be tailored by compositional variation. 15,16 However, analogous to the case of exchange-spring nanocomposites, 17 incorporation of the anisotropy-donor phase (which is the high-coercivity phase in exchange-spring magnets or the antiferromagnetic phase in exchange-bias magnets) is accompanied by a decrease of the overall magnetization, requiring optimization of the nanocomposite phase volume ratio. 18,19 In this current work, the structural and magnetic properties of Ag100-xMnx alloys with Mn concentrations (25 ≤ x ≤ 40 at.%) retained beyond the equilibrium content are reported.…”