Rare-Earth Doped Gd3−xRExFe5O12 (RE = Y, Nd, Sm, and Dy) Garnet: Structural, Magnetic, Magnetocaloric, and DFT Study (original) (raw)
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Gadolinium Yttrium Iron garnet (GdYIG) samples with the chemical formula (Gd x Y 3 À x Fe 5 O 12) (x ¼ 0.0, 0.25, 0.5, 0.75, and 1.0) were prepared via two different methods, the standard ceramic method (SC) and the co-precipitation method (CP). The effect of preparation conditions and Gd 3 þ ion substitution on the phase formation, crystal structure, morphology and magnetic properties were studied. Moreover, the initial permeability μ i and Curie temperature T c were measured for all investigated samples. It was found that, the lattice parameter increases on addition of Gd 3 þ ion while the porosity decreases for both systems of samples. The crystallite sizes of the samples prepared by the (CP) method are smaller than those prepared by (SC) method. The magnetization M s decreases while the coercivity H c increases by increasing the Gd þ 3 concentration in both systems of samples. For the samples prepared by the (SC) method the values of M s are higher than those prepared by (CP) method. Also, it was found that the initial permeability μ i and Curie temperature T c are higher in samples prepared by (SC) method than those prepared by (CP) method. Moreover the magnetic loss (the rate of temperature raise (ΔT/Δt) in an AC magnetic field) was measured for all investigated samples, which increased with increasing Gd concentration. Furthermore, it was found that the samples prepared by (SC) method have magnetic loss higher than those prepared by (CP) method. It was concluded that the preparation method has great effects on the magnetic properties of GdYIG ferrite. The obtained results were explained in the light of Neel's model.
Journal of Applied Physics, 2010
Here we report the single phase nanostructured Gd 3 Fe 5 O 12 garnets with different grain sizes ͑bulk, 75, 47, 35, and 22 nm͒ were prepared by ball milling for various milling times. Both the average grain size and the lattice parameter were estimated from the x-ray diffraction line broadening. The 57 Fe Mössbauer spectra were recorded at 300 and 77 K for the samples with different grain sizes clearly evidenced the formation of Fe 2+ ions induced by milling and the content of Fe 2+ increases with milling time. At 4.2 K, a significant increase in saturation magnetization ͑+11%͒ has been observed for the 47 nm particles. The magnetization is strongly applied field dependent and no saturation effect is observed even at fields as high as of 320 kOe. The results presented here have been explained in terms of the key role played by the Fe 2+ ions.
Mechanochemical decomposition of Gd3Fe5O12 garnet phase
Journal of Magnetism and Magnetic Materials, 2004
Gadolinium iron garnet was milled in a high energy ball mill to study its magnetic properties in the nanocrystalline regime. XRD reveals the decomposition of the garnet phase into Gd-orthoferrite and Gd 2 O 3 on milling. The variation of saturation magnetization and coercivity with milling is attributed to a possible shift in the compensation temperature on grain size reduction and an increase in the orthoferrite content. The M .
Structure and magnetic properties of GdxY1−xFeO3 obtained by mechanosynthesis
Journal of Alloys and Compounds, 2014
Solid solutions of yttrium-gadolinium orthoferrites Gd x Y 1Àx FeO 3 (0 6 x 6 1) were prepared by highenergy ball milling. The aim of this work was to study the influence of the synthesis parameters on the crystal structure and the magnetic behavior of these solid solutions. The precursors, Fe 2 O 3 , Y 2 O 3 and Gd 2 O 3 , mixed in a stoichiometric ratio to obtain these orthoferrites, were milled for different times (up to 5 h). X-ray diffraction and Rietveld refinement were used to elucidate the phase transformation as a function of the milling time. Results showed the complete formation of orthoferrite with an orthorhombic structure (S.G. Pbnm) without any annealing after 5 h of milling for all of the compositions. The effect of the synthesis process and the x value on the crystal structure and the magnetic properties were also studied. All of the synthesized powders demonstrated weak ferromagnetic behavior. In particular, an increase in the maximum magnetization for all the compositions was found, with a maximum that reached 7.7 emu/g for Gd 0.75 Y 0.25 FeO 3 . For Gd 0.5 Y 0.5 FeO 3 , the magnetization decreases down to 2.1 emu/g. A small contamination of metallic Fe was confirmed through electron spin resonance experiments.
Magnetocaloric effect in bulk and nanostructured Gd 3 Fe 5 O 12 materials
Journal of Physics D: Applied Physics, 2009
We report here the magnetocaloric effect (MCE) in bulk and nanostructured gadolinium iron garnets (Gd 3 Fe 5 O 12 ). When compared with the bulk counterpart, the magnitude of the MCE is smaller for nanostructured samples with an average grain size of 50 nm, but increases when the grain size decreases to 35 nm. For the bulk sample, the MCE curves show a broad peak at 35 K; this peak is found to shift to lower temperatures for the nanostructured samples. The origin of the MCE peak for the bulk sample is associated with the intrinsic magnetic frustration and the ferromagnetic ordering of the Gd sublattice below 90 K, while for nanostructured garnets it is additionally ascribed to the surface spin disorder and particle blocking effects. While blocking is detrimental to achieving large MCE, surface spin disorder is found to enhance it under high applied fields.
Specific features of Eu 3+ and Tb 3+ magnetooptics in gadolinium-gallium garnet (Gd 3Ga 5O 12)
Journal of Rare Earths, 2011
We reported magnetooptical properties of Eu3+(4f(6)) and Tb3+(4f(8)) in single crystals of Gd3Ga5O12 (GGG), Y3Ga5O12 (YGG), and Eu3+(4f(6)) in Eu3Ga5O12 (EuGG) for both ions occupying sites of D2 symmetry in the garnet structure. Absorption, luminescence, and magnetic circular polarization of luminescence (MCPL) spectra of Tb3+ in GGG and YGG and absorption and magnetic circular dichroism (MCD) of Eu3+ in EuGG were studied. The data were obtained at 85 K and room temperature (RT). Magnetic susceptibility of Eu3+ in EuGG was also measured between 85 K and RT. The magnetooptical and magnetic susceptibility data were modeled using the wavefunctions of the crystal-field split energy (Stark) levels of Eu3+ and Tb3+ occupying D2 sites in the same garnets. The results reported gave a precise determination of these Stark level assignments and confirmed the symmetry labels (irreducible representations) of the closely-spaced Stark levels (quasi-doublets) found in the 5D1 (Eu3+) and 5D4 (Tb3+) multiplets. Ultraviolet (UV) excitation (<300 nm) of the 6PJ and 6IJ states of Gd3+ in the doped GGG crystals led to emission from 5D4 (Tb3+) and 5D1 and 5D0 (Eu3+) through radiationless energy transfer to the 4f(n−1)5d band of Tb3+ and to UV quintet states of Eu3+. The temperature-dependent emission line shapes and line shifts of the magnetooptical transitions excited by UV radiation suggested a novel way to explore energy transfer mechanisms in this rare-earth doped garnet system.
The preferential site occupation and magnetic properties of GdxY2−xO3
Journal of Physics and Chemistry of Solids, 1993
Abstra&-The gadolinium-yttrium mixed oxides Gd,Y,_,O, were synthesized over a wide range of concentrations: x = 0.10, 0.18, 0.41, 0.74 and 1.26. The X-ray diffraction data from the polycrystalline samples were taken at room temperature and refined using the Rietveld method. Gadolinium-yttrium oxides crystallize in the space group Ia3. The cations occupy the six coordinated positions 8b and 24d. The anion occupies a general tetrahedrally coordinated position. At concentrations x Q 0.41 gadolinium ion occupies exclusively 24d, but at higher concentrations the occupation of position 86 increases continuously. The magnetic susceptibility measurements showed the presence of the antiferromagnetic interaction in all samples. The magnetic moment in the sample x = 1.26 is significantly different from the magnetic moment of the free ion Gd 3+. The Cur&Weiss temperature shows a nonlinear dependence on concentration.
Microstructure and magnetic properties of yttrium-iron garnet prepared by a sol–gel method
Yttrium iron garnet particles were synthesized by the sol-gel method of auto-combustion. Their crystalline structures and magnetic properties were investigated by using X-ray diffraction (XRD), vibrating sample magnetometer (VSM), and Mössbauer spectrum. The crystallite size and magnetic properties were observed and studied. The size of magnetic nanoparticles increased with increasing calcination temperature. The study of magnetic properties by VSM at room temperature showed that the samples are ferromagnetic, having the specific magnetizations of 20,6, 19 and 18.3 emu/g for Y3Fe5O12 samples calcined at 900, 1000, and 1100°C, respectively. It is concluded that samples prepared via sol gel technique appear to be an attractive route due to the possible reduction of cost of production and the enhanced magnetic and structural properties of the sample.
Ceramics International, 2020
Yttrium iron garnet (YIG) nanoparticles (NPs) doped with rare earth (RE) metal ions (Y 2.5 Sm 0.5 Fe 5 O 12 , Y 2.5 Nd 0.5 Fe 5 O 12) were successfully synthesized by sol-gel auto combustion approach. The cubic crystalline structure and morphology of the prepared garnet ferrite NPs were analyzed by X-ray diffractometer (XRD) and field emission scanning electron microscopy (FESEM). The cubic crystalline garnet phase of the synthesized YIG, Sm-YIG and Nd-YIG samples was successfully achieved at 950°C sintering temperature. The force constant and absorption bands were estimated by using Fourier transform infrared spectroscopy (FTIR). The doping effect of RE metal ions on the chemical states of YIG were examined by x-ray photoelectron microscopy (XPS). The valence band (from 12.63 eV to 13.22 eV), conduction band (from 10.89 eV to 11.34 eV) edges and optical bandgap values of RE doped YIG samples were calculated using UV-Vis spectroscopy and ultraviolet photo electron spectroscopy (UPS). The magnetic analysis of the prepared NPs was studied using vibrating sample magnetometer (VSM). The XPS analysis of RE doped YIG samples exhibit the existence of RE (Sm +3 , Nd +3) contents on the surface of YIG ferrite by decreasing the oxygen lattice in garnet structure. The optical bandgap (from 1.74 eV to 1.88 eV) explains the semiconducting nature of the synthesized NPs. The UPS results confirm the valence band position of YIG doped samples. The saturation magnetization and remanence of RE doped garnet ferrite samples increased from 13.45 to 18.83 emu/g and 4.06-6.53 emu/g, respectively.
Magnetic moments in a gadolinium iron garnet studied by soft-X-ray magnetic circular dichroism
The magnetic moments of Gd and Fe in gadolinium iron garnet (Gd3FesO~2) were probed at 77 and 300 K by soft-X-ray magnetic circular dichroism (SXMCD) measurements at the GdMa. s and at the Fe L2. 3 absorption edges. The SXMCD signal at each edge allows one to independently determine the magnetic ordering for each specific ion, and the temperature dependence confirms that the reversal of the macroscopic magnetization is due to the reversal of each local magnetic moment of the Fe and the Gd atoms when the compensation point (Tc,,m p = 288 K) is crossed. This work therefore demonstrates that SXMCD can probe element and site specific magnetic properties of multi-component systems.