Control of magnetic properties in spinel ZnFe2O4 thin films through intrinsic defect manipulation

Abstract

We present a systematic study of the magnetic properties of ZnFe2O4 thin films fabricated by pulsed laser deposition at low and high oxygen partial pressure and annealed in oxygen and argon atmosphere, respectively. The as-grown films show strong magnetization, closely related to a non-equilibrium distribution of defects, namely, Fe cations among tetrahedral and octahedral lattice sites. While the concentration of tetrahedral Fe cations declines after argon treatment at 250 °C, the magnetic response is enhanced by the formation of oxygen vacancies, evident by the increase in near-infrared absorption due to the Fe2+–Fe3+ exchange. After annealing at temperatures above 300 °C, the weakened magnetic response is related to a decline in disorder with a partial recrystallization toward a less defective spinel configuration.

Spinel Cu–Mn–Cr Oxide Nanoparticle-Pigmented Solar Selective Coatings Maintaining >94% Efficiency at 750 °C

“…Since Cr 3+ and Mn 4+ have the strongest tendency to compete for octahedral sites based on OSPE, tuning their percentages may further optimize Cu 2+ and Mn 3+ site inversion for better solar selectivity. In addition, oxygen vacancies, as identified in our previous analyses, further lower the ligand symmetry to enhance the oscillation strength of d-d optical absorption especially in the NIR solar spectral regime at 0.5–1 eV, as has been reported in spinel ZnFe 2 O 4 system . Therefore, these two factors work synergistically to enhance the overall solar selectivity.…”

“…In addition, oxygen vacancies, as identified in our previous analyses, further lower the ligand symmetry to enhance the oscillation strength of d-d optical absorption especially in the NIR solar spectral regime at 0.5-1 eV, as has been reported in spinel ZnFe2O4 system. 28 Therefore, these two factors work synergistically to enhance the overall solar selectivity. Figure 3a shows a photograph of an Inconel 625 tube section (outer diameter=76 mm) coated with the spinel Cu-Mn-Cr oxide NP-pigmented silicone solar selective absorber and annealed in air at 750ºC for 24h.…”

Nanostructured ZnFe2O4: An Exotic Energy Material

“…Thus, simultaneous measurement of saturation magnetization and conductivity can be used as a tool to approximate cation inversion in the ZnFe 2 O 4 compound. However, in an oxygen-deficient growth regime, the likely inverted spinel structure is [42,43] [(Zn 2+ ) 1 [44]. These transformations greatly affect the magnetic, electric, and optical properties of ZnFe 2 O 4 nanostructures.…”

“…Thus, simultaneous measurement of saturation magnetization and conductivity can be used as a tool to approximate cation inversion in the ZnFe 2 O 4 compound. However, in an oxygen-deficient growth regime, the likely inverted spinel structure is [ 42 , 43 ] [(Zn 2+ ) 1−x−y (Fe 3+ ) x+y ] A [(Zn 2+ ) x (Fe 2+ ) y (Fe 3+ ) 2−x−y ] B (O 2− ) 4−δ wherein partial reduction of Fe +3 into Fe +2 is expected at B sites. For a higher oxygen-deficient growth regime, now there is no Zn +2 ions are available at B sites and inverted spinel structure is represented a [ 17 ] [(Zn 2+ ) x (Fe 3+ ) 1−x ] A [(Fe 2+ ) 1−x (Fe 3+ ) 1+x ] B (O 2− ) 4−δ akin to the Zn doped Fe 3 O 4 (Zn y Fe 3 − y O 4 ) compound.…”

Room-temperature spin glass behavior in zinc ferrite epitaxial thin films

“…Besides that, zinc ferrite thin films can also be considered as an interesting semiconducting material in spintronics with tunable magnetic properties [4,6,[11][12][13]. A variety of reports of different types of magnetic order in zinc ferrite can be found throughout the literature ranging from ferro(i)magnetic [4,6,[13][14][15][16][17], to superparamagnetic [8,11,18,20,21] and to spin glass behavior [7,9,19,22]. Note, that in some cases superparamagnetism with interparticle interactions is associated with a so-called cluster-glass behavior [7,8,19].…”