Origin of the Intrinsic Coercivity Field Variations and Magnetic Study of ε-Fe2O3

Preparation and Characterization of Fe2O3-SiO2 Nanocomposite for Biomedical Application

“…Conclusively, it is important to notice that all hysteretic curves (except Figure 6(b)), referring to the sample containing the only hematite phase, observed at lower temperature in comparison with the other investigated samples) could be classified as hysteretic loops having constricted middles (wasp-waisted loops). Generation of wasp-waisting curves appears as a result of two population of the particles characterized by distinct coercivity spectra; numerical simulations reveals that wasp-waisting curves requires and SPM contribution [68], that is confirmed by Figures 4(b) and 1(b) [58]. Experimental results shown in Figures 2(a) and 3(a) revealed that the decrease of measured magnetic field value of the samples is not a certain parameter that indicates vanishing of the other iron oxide polymorphs and the presence of the pure hematite nanoparticles.…”

“…Experimental results shown in Figures 2(a) and 3(a) revealed that the decrease of measured magnetic field value of the samples is not a certain parameter that indicates vanishing of the other iron oxide polymorphs and the presence of the pure hematite nanoparticles. Moreover, represented results pointed out that ε-Fe 2 O 3 → α-Fe 2 O 3 phase transformation cannot be the decisive factor on the coercivity value of the nanocomposite material (Figures 1-4) [58]. The variation of the initial iron ion precursor amount [60] enables the alteration of measured magnetic field value without changing the phase composition of the nanocomposite material.…”

“…(3)][58]:H crit = f (α, β, γ, δ, ε, η, θ, ι, κ)(3) Mineralogy -Significance and Applications 8 The main influence on the coercivity value arises from: a. Synthesis conditions (parameter α) b. Presence of different iron oxide species in the investigated sample (parameter β) c. Contribution originated from the physical and chemical properties of the SiO 2 matrix, such as pore size distribution or the flow of different gases through the matrix (parameter γ) d. Angular distribution of the nanoparticle orientations (parameter δ) e. Particle size and shape distribution (parameter ε)…”

Nuclear forward scattering application to the spiral magnetic structure study in ε−Fe2O3

“…It is determined by the parameter u = 4J j j S j 3J i j S i , where i and j are the indices of the magnetic sublattices, J i j is the integral of the exchange interaction between the sublattices, and S i and S j are the spins of the sublattices, which, in our case, are equal to each other. According to Kaplan's criterion [35], the collinear configuration for tetragonal spinels exists below the critical value of this parameter u = 8 9 . For -Fe 2 O 3 , the value of this parameter for the magnetic sublattice of a tetrahedron is much higher: u = 1.46.…”

“…The -Fe 2 O 3 magnetic structure undergoes a complex evolution, which especially concerns the well-known transition at 80-150 K [7]. This transition is accompanied by a huge change in the coercivity [7,8]. In view of recent developments [9], the temperature of the transition to the paramagnetic state seems ambiguous.…”