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

Abstract

The -Fe 2 O 3 magnetic structure has been analyzed using the synchrotron radiation source. Time spectra of nuclear forward scattering for isolated nanoparticles with an average size of 8 nm immobilized in a xerogel matrix have been recorded in the temperature range of 4-300 K in applied magnetic fields of 0-4 T in the longitudinal direction at the European Synchrotron Radiation Facility (ESRF, Grenoble, France). It has been found that the external magnetic field does not qualitatively change the H hf (T) behavior, but makes a strong opposite impact on the hyperfine fields in the nonequivalent iron sites, leading to the divergence of H hf polar angle dependences below 80 K. A complete diagram of the -Fe 2 O 3 magnetic structure in the temperature range of 4-300 K is proposed. At 300 K, the -Fe 2 O 3 compound is confirmed to be a collinear ferrimagnet. The experimental results show that the magnetic transition at 150-80 K leads to the formation of a noncollinear magnetic structure. Furthermore, in the range of the 80-4 K, the ground state of a magnetic spiral is established. The experimental results are supplemented by the analysis of the exchange interactions and temperature dependence of the magnetization in a magnetic field of 7 T.

Flux growth and phase diversity of the triple oxides of transition metals (Mn,Fe,Ga)2O3in multicomponent fluxes based on Bi2O3–MoO3–B2O3–Na2O

“…The occurrence of iron in the tetrahedral positions is a characteristic of the crystal structure of the spinel, 32 which includes samples 3(2) (spinel phase) and 7. We also note that the tetrahedral environment of iron is observed in orthorhombic sample 8, which has the crystal structure of the ε-Fe 2 O 3 type, 34,35 in which 25% of the cations have a tetrahedral environment. It is noteworthy that the synthesis conditions made it possible to change the tendency for iron to occupy tetrahedral positions in the crystal structure of ε-Fe 2 O 3 .…”

An effect of scandium substitution on the phase purity and structural, magnetic, and electrochemical features of ε-Fe2O3 nanoparticle systems

“…8,13,14,21 However, some works reported other low-temperature ground magnetic states which resemble features of a canted antiferromagnet with a canting angle different from that above ∼150 K. 8,19 Recently, it was suggested that as a result of strong frustrations of the ε-Fe 2 O 3 magnetic structure, a series of magnetic transitions occur upon cooling from ∼150 K down to ∼80 K, encouraging the formation of non-collinear magnetic arrangement with the magnetic spiral as a ground magnetic state of the system. 75 Moreover, a field-induced transition was witnessed at a temperature interval from ∼50 K to ∼80 K; 76 however, its nature has not been clearly understood yet. In an early study, a metamagnetic transition was suggested to occur at around 50 K; 19 however, no attention has been devoted to systematically study this phenomenon so far and thus, it remains a questionable issue.…”

Resonance Frequency Tuning of a 200 GHz Band Absorber by an External Magnetic Field

“…Epsilon iron oxide (ε‐Fe 2 O 3 ) nanomagnets are attractive because they have been reported to exhibit a large coercive field and high‐frequency millimeter‐wave absorption at 182 GHz by zero‐field ferromagnetic resonance (the so‐called natural resonance). [ 17–48 ] Metal‐substituted epsilon iron oxide (ε‐ M x Fe 2− x O 3 : M = Al 3+ , Ga 3+ , and In 3+ ) and Ti 4+ −Co 2+ cosubstituted series, ε‐(TiCo) x Fe 2− x O 3 , exhibit zero‐field ferromagnetic resonance over a wide frequency range of 35–182 GHz. Rhodium‐substituted epsilon iron oxide, ε‐Rh x Fe 2− x O 3 , shows even higher resonance frequencies above 182 GHz by increasing the Rh/Fe ratio.…”