Magnetic and resonant properties of ferrite compositions (1  −  x)MeFe₂O₄ · xP₂O₅ prepared by plasma spraying

Abstract

It was found that after plasma spraying and rapid quenching of ferrite compositions (1x)MeFe 2 O 4 •xP 2 O 5 within the range of 0.35<x<0.4 for any considered compounds, transition to the X-ray-amorphous state is observed (so called concentration depended transition (CDT). This transition occurs along with modification of X-ray and Mössbauer spectra (quadrupole splitting into isomer shift) and changing their magnetic parameters: a saturation magnetization σ s , a coercive field H c and a line width of ferromagnetic resonance (FMR) ∆H. The abnormal increase of saturation magnetization σ s is revealed at Т < 100 K. Particularities of changing the Curie temperature T c and a saturation magnetization σ s at different rates of quenching ferrites from the liquid state are discussed. Highlights:• We studied the influence of the ferrite compositions inclusion on their magnetic state;• We studied the behavior of the magnetic parameters (T c , σ s , H c ) of spinel ferrites under different conditions of rapid quenching;• We studied the γ-spectra of ferrite compositions;• We studied the behavior of the magnetic parameters H c and ∆H at concentration transitions (CDT).Therefore, searching new ferromagnetic materials has been mainly carried out for the purpose of creating multi-component compounds with complex chemical composition [1][2][3][4]. This approach is aimed at the possibility of selective injection of various ions into the sublattice, with the consequent changes of the character and the ratio of intra-and inter-sublattice exchange interactions, and as a result, changes of the magnetic properties of these compounds. In this respect, the investigation was focused on defining of the compositionproperty regularities.An alternative approach in the production of new materials appeared because of the possibility to influence the oxide compounds by concentrated energy flows (plasma, laser, etc.).This enables rapid heating and subsequent ultra-fast quenching of the melt [5][6][7][8][9][10][11]. After corresponding treatment, a number of changes are observed in the structure and properties of the substances. They are as follows: decrease of the crystallite size, increase of material disorder, increase of solubility limit for the components in multiphase systems, formation of metastable crystalline phases, redistribution of cations at sublattice points, as well as partial or complete amorphization of the compound. Due to strong correlation between the structural state, the type of spin ordering and the set of magnetic characteristics of the oxides, determining the correlation Structure -Disorder state -Property would provide direct control of the ferrite properties.Compared to metal alloys, ferrites with spinel structure are prone to amorphization significantly less and are prone to thermal conductivity much less (by several orders). Therefore the production of iron oxides in the X-ray amorphous state is quite difficult because of achieving rather high rate of quenching the melt.Widely known amorphizing additions such as B 2 O...

Low-temperature magnetic behavior of nanostructured ferrite compositions prepared by plasma spraying

“…Such a large discrepancy in the magnitudes of the magnetic anisotropy constant is probably due to the presence of other mechanisms in its formation, or due to a much smaller size of the nanoparticles (< 5 nm). In favor of the latter assumption, the data of γ-resonance spectroscopy (γ-spectra is modified into a doublet) indicate the absence of long-spin ordering in nickel ferrite compositions (at x > 4) [18]. In this case, the magnetic structure represents clusters formed by the near magnetic order.…”

“…Thus, the structural disorder and amorphization of ferrite compositions was achieved by diluting the original ferrite with the amorphizing agent (P 2 O 5 ), followed by rapid quenching of molten droplets on a copper disk. The results of the morphological and structural studies of the produced samples are given in [11][12][13]18].…”

“…X-ray amorphous materials were produced, in some cases, at high concentrations of the amorphizing agent (> 40%). The structural disorder involved in this process causes changes in the equilibrium distribution of cations on sublattices [9,11,18]. This leads to the frustration of exchange coupling and modification of intrasublattice and intersublattice exchange interactions, and consequently to the formation of a new magnetic state and new magnetic properties of the compositions.…”

The morphological and structural features of ferrite compositions (1−x) MeFe2O4 xP2O5 prepared by plasma spraying

“…This is due to the spinel structure, which is stable under thermodynamically non-equilibrium statistical distribution of cations through sublattices and remains stable under significant deviations from stoichiometry. On the other hand, glass-forming additives (B 2 O 3 , SiO 2 , P 2 O 5 , and others) are known to reduce the critical cooling rate during the transition of compound up to the amorphous state and can facilitate amorphization of ferrites [11,12,14]. Thus magnetic ordering is observed in borate, silicate and phosphate glass [13,15,16].…”