High field Mössbauer effect study of LaFe12O19

Synthesis and magnetic properties of La-substituted M-type Sr hexaferrites

“…This peculiar shape of the M(T) curves in hexaferrites is due to the temperature dependence of the magnetic moments of ferrous ions on the 12k site. Such temperature variations of the hyperfine fields of the 12k sites and the subsequent increase of curvature of M(T) with x have already been demonstrated for Sr 1Àx La x Fe 12Àx Co x O 19 ferrites [17,18].…”

“…This valence state occurs in the 2a site [18]. Thus, in La-containing samples, a sixth contribution, namely (Fig.…”

Hexagonal ferrites of X-, W-, and M-type in the system Sr–Fe–O: A comparative study

“…It is well established that in the M-type LaFe 12 O 19 phase, the complete substitution of Sr 2 þ for La 3 þ leads to a change of the valence state of iron ions in the 2a site from Fe 3 þ to Fe 2 þ due to the introduction of La 3 þ ion instead of Sr 2 þ ion to compensate for the excess of positive charges [26][27][28]; analogous conclusions arise from the analysis of NMR measurements in M-type hexaferrites with partial or full substitution of La 3 þ in the heavy cations sites [29]. Fe 2 þ ions being thus located in the 2a octahedral sites of the S-blocks in the M-type ferrite, we assumed by comparing the crystal structure of the three phases, that the Fe 2 þ ions occupy four magnetic a sites corresponding to the 4f VI (or 4f 3 ) and 6g octahedral sites in the SS and S-S blocks of the W unit cell and six magnetic a sites corresponding to the 3b VI, 9e VI and 6c VI octahedral sites in the S-, S-S-and SS-blocks of the X-unit cell, respectively.…”

Structural and magnetic properties of barium hexaferrites with Gd–Co substitution

“…The appearance of ferrous ions is attributed to La 2 O 3 [12], as a consequence of the replacement of Ba 2+ or Sr 2+ by La 3+ in the hexaferrite crystal lattice [14]. Moessbauer studies in La hexaferrite designated Fe 2+ site preference [15,16], with the 2a sublattice being mostly favored. In LaCo hexaferrites, the presence of Fe 2+ ions in the 2a site and the preference of Co 2+ ions for the 4f 2 and 2a sites have been concluded [8][9][10], and the incorporation of La in the hexaferrite structure has been indirectly evidenced.…”