The effect of gadolinium substitution in inverse spinel nickel ferrite: Structural, Magnetic, and Mössbauer study

Effect of Terbium Ion Substitution in Inverse Spinel Nickel Ferrite: Structural and Magnetic Study

“…The higher frequency band (ν 1 ) was found to shift from 554.3 cm −1 to 543.3 cm −1 while the lower frequency band (ν 2 ) shifted from 413.5 cm −1 to 406.2 cm −1 . Similar band shifting with the doping in NiFe 2 O 4 has been reported in the literature [16,27,32,33]. The difference in the band positions is expected because of the difference in the Fe-O distances for the A and B sites.…”

“…The ionic radius of a rare-earth ion is larger than the tetrahedral site radii, and therefore energetics force the rare-earth ions to occupy octahedral sites. The preferred rare-earth occupancy for the octahedral site has been also corroborated by Mossbauer spectroscopy [16,20]. Figure 1c shows the infrared absorption spectra of samples.…”

“…Different types of magnetic [8,9] and nonmagnetic atoms for cations [10][11][12][13][14][15] have been explored to create atomic-level changes in ferrites. This selection affects the Fe 3+ -O 2− -Fe 3+ interaction, which changes the crystal structure of ferrites and hence the magnetic properties of the compound [16].…”

“…Aside from replacing Fe 3+ ions with magnetic and non-magnetic ions, researchers have studied the substitution of rare-earth elements [16,19,20]. Larger ionic radii of the rare-earth ions compared to Fe 3+ were observed to bring lattice expansion in ferrites, which can alter the superexchange interaction of Fe 3+ -O 2− -Fe 3+ [21].…”

“…Larger ionic radii of the rare-earth ions compared to Fe 3+ were observed to bring lattice expansion in ferrites, which can alter the superexchange interaction of Fe 3+ -O 2− -Fe 3+ [21]. It has been observed that the substitution of rare-earth elements such as Nd 3+ , Gd 3+ , Ho 3+ , Er 3+ , Tm 3+ , Y 3+ , and Lu 3+ decreases the Curie temperature [16,20,22] compared to pure ferrites, and become more useful for magneto-optical recording [20,23]. Additionally, the substitution of rare-earth ions at the octahedral site affects the hole transfer rate between Ni 2+ and Ni 3+ , which increases the electrical resistivity of the compound and hence enables its high-frequency application.…”