Mössbauer study on Y-type hexaferrite Ba2Mg2Fe12O22

Abstract

Mössbauer study on a Y-type hexaferrite Ba 2 Mg 2 Fe 12 O 22 has been conducted by using a single crystal specimen. The spins are in the c-plane down to 60 K. For 18h VI site Fe, the quadrupole shifts and the outermost line width change around 195 K, where the transition from ferrimagnetic to proper screw spin structure takes place. Below 50 K, the spin reorientation transition to a longitudinal conical structure was also recognized. At 16 K, the spins incline about 15 • from the c-plane.

Study of the Structural and Magnetic Properties of Co-Substituted Ba2Mg2Fe12O22 Hexaferrites Synthesized by Sonochemical Co-Precipitation

“…The Mӧssbauer spectral shape of Ba 2 Mg 0.4 Co 1.6 Fe 12 O 22 and Ba 2 Mg 0.5 Co 1.5 Fe 12 O 22 are very similar suggesting that no changes occurred in the iron oxidation state and local environment of iron as the Co content was raised [35]. A good-quality fit of the Mössbauer spectrum of Ba 2 Mg 0.4 Co 1.6 Fe 12 O 22 was obtained by using only four doublets attributed to three Fe 3+ components in Ba 2 Mg 0.4 Co 1.6 Fe 12 O 22 [36], which is in good agreement with the Mössbauer results of the non-substituted Y-type hexaferrite Ba 2 Mg 2 Fe 12 O 22 , in which three different electric field gradient (EFG) axes with respect to the spin direction [110] have been shown [18]. Indeed, the Mössbauer spectrum of Ba 2 Mg 0.4 Co 1.6 Fe 12 O 22 is a superposition of three sub-spectra originating from the six different iron positions as revealed by Nakamura et al [18].…”

“…These majority spins and minority spins determine the two magnetic sublattices different from crystal structural blocks— L m (spins in octahedral 3 a , 3 b , and 18 h sites) and S m (spins in tetrahedral 6 c T and 6 c S and octahedral 6 c sites) blocks alternating along [001], which bear, correspondingly, opposite large and small magnetization M [11]. For Ba 2 Mg 2 Fe 12 O 22 at temperatures exceeding room temperature (below 553 K), a ferrimagnetic spin arrangement sets in, and below 195 K a proper screw spin structure (helical) was identified [17,18]. The turn angle of the helix is about 70° [13].…”

“…They found that the transition temperature from a ferromagnetic to a helical spin arrangement increases with increasing the cobalt concentration, and for x = 1.6 it is 226 K. In the case of Ba 2 Co 2 Fe 12 O 22 (fully substituted), this magnetic phase transition occurs at 225 K [22] and the M s and H c are 32 emu/g and 70 Oe, respectively [23,24]. The Co substitution also increases the Curie temperature from 553 K for Ba 2 Mg 2 Fe 12 O 22 to 613 K for Ba 2 Co 2 Fe 12 O 22 [17,18,22].…”

Study of Quasi-Monophase Y-Type Hexaferrite Ba₂Mg₂Fe₁₂O₂₂ Powder

“…Ba2Mg2Fe12O22 consists of two magnetic sublattice blocks, L and S blocks, stacked alternately along the [001] axis, which bear, respectively, the opposite large and small magnetization M, causing ferrimagnetism even at high temperatures exceeding room temperature. The Curie point of Ba2Mg2Fe12O22 is 553 K. Below 195 K, the spins form a proper screw spin structure with the propagation vector along the c-axis at B = 0 [10,11]. The turn angle of the helix is about 70° [12].…”

Carrier mobility of iron oxide nanoparticles supported on ferroelectrics studied by Mössbauer spectroscopy

“…Small peaks originating from Fe were apparent but the crystal structures could not be identified, because the content of Fe was too low and Fe oxides particles were too small. So we used 57 Fe Mössbauer spectroscopy which was conducted in conventional transmission geometry by using 57 Co-in-Rh (25 mCi) as the γ ray source [6]. The powder type sample was set in a vacuum furnace for the high temperature measurements (10 −2 Torr, up to 773 K) or in a closed cycled cryostat for the low temperature measurements.…”