Structural and Magnetic Properties of Ln2CoMnO6(Ln=Dy and La) Produced by Combustion Synthesis
01 Jul 2013-Journal of Superconductivity and Novel Magnetism (Springer US)-Vol. 26, Iss: 7, pp 2521-2524
TL;DR: In this article, the structural and magnetic properties of the Ln2MnCoO6 (Ln=La and Dy) produced by the combustion method are reported, and the samples were characterized by X-ray diffraction with Rietveld refinement, and their magnetic properties by studying the dependence of the magnetization with the magnetic field and temperature.
Abstract: In this article, the structural and magnetic properties of the Ln2MnCoO6 (Ln=La and Dy) produced by the combustion method are reported. The samples were characterized by X-ray diffraction (XRD) with Rietveld refinement, and their magnetic properties by studying the dependence of the magnetization with the magnetic field and temperature. XRD analysis reveals that the La2MnCoO6 (LCM) consists of a mixture of crystalline orthorhombic, monoclinic, and rhombohedral phases. This mixture might be originated by the mixing of valence states of the Co+2/Mn+4 and Co+3/Mn+3. Dy2CoMnO6 (DCM) presents a mixed composition of hexagonal and orthorhombic structures with the transition metal atoms in mixed valences. Magnetic measurements show that the magnetic transition temperature T
C
decreases from 150 K to 85 K when the La ions are replaced by Dy. We also observe that the magnetic order changes from a ferromagnetic to a ferrimagnetic when La is replaced by Dy.
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TL;DR: In this paper, the Dy2CoMnO6 double perovskite nanostructures with various morphologies such as urchin-like, flower-like and needle-shaped nanorods were prepared by utilizing various chelating agents and crosslinker agents.
Abstract: For the first time, urchin-like Dy2CoMnO6 double perovskite nanostructures have been successfully synthesized via an improved Pechini method. Herein, Dy2CoMnO6 nanostructures with various morphologies such as urchin-like, flower-like, needle-shaped nanorods were prepared by utilizing various chelating agents and cross-linker agents. The as-synthesized Dy2CoMnO6 nanostructures were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, field emission scanning electron microscopy and UV–Vis diffuse reflectance spectroscopy. Moreover, the photocatalytic performance of as-prepared Dy2CoMnO6 nanostructures was evaluated by photodegradation of methylene blue, rodamin B and erythrosine dyes as water contaminants under ultraviolet light illumination.
34 citations
Cites background or methods from "Structural and Magnetic Properties ..."
...Double perovskite M2CoMnO6 (M = La and Dy) micro/ nanostructures have been synthesized by employing various methods including sol–gel [3], combustion [11], solidstate reaction [12], molten-salt reaction [13], co-precipi-...
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...2a–c) show double perovskite Dy2CoMnO6 phase with a small amount of unreacted dysprosium oxide [11]....
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TL;DR: In this article, a phase pure double perovskite La2FeMnO6 compound was synthesized using high temperature solid-state reaction method, which has a cubic structure with space group Pm-3m.
29 citations
TL;DR: In this article, a detailed investigation of the crystal structure, magnetic, and magnetocaloric properties of the ordered monoclinic polycrystalline double perovskite Ho 2 CoMnO 6 (HCMO) compound was performed.
Abstract: The strong coupling between 3d and 4f based magnetic sublattices in double perovskite (DP) compounds results in various exotic complex magnetic interactions, and the ground state contains multiple fascinating and remarkable magnetic states. In this article, we have performed a detailed investigation of the crystal structure, magnetic, and magnetocaloric properties of the ordered monoclinic polycrystalline double perovskite Ho 2 CoMnO 6 (HCMO) compound. A study of the magnetization dynamics employing temperature and magnetic field shows a powerful correlation between Ho and Co/Mn sublattices. Due to the presence of the ferromagnetic superexchange interaction in between Co 2 + − O − Mn 4 + networks, the system undergoes an ordered state at the transition temperature, T C ≈ 77 K. Below T C, a clear compensation point continued by negative magnetization is noticed in the virgin state of the compound. The reduction of the saturation magnetization ( M S) in the hysteresis curves (M-H) can be explained by the existence of local anti-site defects or disorders and anti-phase boundaries in the system. Temperature dependence of magnetic entropy change ( − Δ S) curves shows a maximum value of 13.4 J/kg K for Δ H = 70 kOe at a low temperature along with a noticeable inverse magnetocaloric effect. Moreover, the material holds reasonable values of magnetocaloric parameters. The absence of thermal hysteresis along with a large value of | Δ S | makes the system a potential candidate for low temperature as well as liquid nitrogen temperature-based magnetic refrigeration. Additionally, our experimental findings should encourage further detailed studies on the complex 3d–4f exchange interaction in the double perovskite system.
27 citations
TL;DR: In this paper, the structural and magnetic properties of Dy2CoMnO6, Dy2NiMnNO6 and Gd2CmnO6 double perovskites were investigated using X-ray powder diffraction and squid magnetometry.
Abstract: The structural and magnetic properties of the Dy2CoMnO6, Dy2NiMnO6 and Gd2CoMnO6 double perovskites are investigated using X-ray powder diffraction and squid magnetometry. The materials adopt an or ...
22 citations
TL;DR: In this article, the structural, microstructural, dielectric, impedance, modulus, leakage-current and magnetic characteristics of a double perovskite compound Dy2CoMnO6 have been reported.
15 citations
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TL;DR: In this paper, the authors present materials at the practical rather than theoretical level, allowing for a physical, quantitative, measurement-based understanding of magnetism among readers, be they professional engineers or graduate-level students.
Abstract: Introduction to Magnetic Materials, 2nd Edition covers the basics of magnetic quantities, magnetic devices, and materials used in practice. While retaining much of the original, this revision now covers SQUID and alternating gradient magnetometers, magnetic force microscope, Kerr effect, amorphous alloys, rare-earth magnets, SI Units alongside cgs units, and other up-to-date topics. In addition, the authors have added an entirely new chapter on information materials. The text presents materials at the practical rather than theoretical level, allowing for a physical, quantitative, measurement-based understanding of magnetism among readers, be they professional engineers or graduate-level students.
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TL;DR: In this paper, it was shown that both electrical conduction and ferromagnetic coupling in these compounds arise from a double exchange process, and a quantitative relation was developed between electrical conductivity and the Ferromagnetic Curie temperature.
Abstract: Recently, Jonker and Van Santen have found an empirical correlation between electrical conduction and ferromagnetism in certain compounds of manganese with perovskite structure. This observed correlation is herein interpreted in terms of those principles governing the interaction of the $d$-shells of the transition metals which were enunciated in the first paper of this series. Both electrical conduction and ferromagnetic coupling in these compounds are found to arise from a double exchange process, and a quantitative relation is developed between electrical conductivity and the ferromagnetic Curie temperature.
5,097 citations
TL;DR: In this paper, it was shown that if the total electronic state of orbital and spin motion is degenerate, then a non-linear configuration of the molecule will be unstable unless the degeneracy is the special twofold one (discussed by Kramers 1930) which can occur only when the molecule contains an odd number of electrons.
Abstract: In a previous paper (Jahn and Teller 1937) the following theorem was established: A configuration of a polyatomic molecule for an electronic state having orbital degeneracy cannot be stable with respect to all displacements of the nuclei unless in the original configuration the nuclei all lie on a straight line. The proof given of this theorem took no account of the electronic spin, and in the present paper the justification of this is investigated. An extension of the theorem to cover additional degeneracy arising from the spin is established, which shows that if the total electronic state of orbital and spin motion is degenerate, then a non-linear configuration of the molecule will be unstable unless the degeneracy is the special twofold one (discussed by Kramers 1930) which can occur only when the molecule contains an odd number of electrons. The additional instability caused by the spin degeneracy alone, however, is shown to be very small and its effect for all practical purposes negligible. The possibility of spin forces stabilizing a non-linear configuration which is unstable owing to orbital degeneracy is also investigated, and it is shown that this is not possible except perhaps for molecules containing heavy atoms for which the spin forces are large. Thus whilst a symmetrical nuclear configuration in a degenerate orbital state might under exceptional circumstances be rendered stable by spin forces, it is not possible for the spin-orbit interaction to cause instability of an orbitally stable state. 1—General theorem for molecules with spin Just as before we must see how the symmetry of the molecular framework determines whether the energy of a degenerate electronic state with spin depends linearly upon nuclear displacements. This is again determined by the existence of non-vanishing perturbation matrix elements which are linear in the nuclear displacements. These matrix elements are integrals involving the electronic wave functions with spin and the nuclear displacements, and we deduce as before from their transformation properties whether for a given molecular symmetry they can be different from zero.
2,539 citations
TL;DR: The results show that the notion of ``double exchange'' must be generalized to include changes in the Mn-Mn electronic hopping parameter as a result of changes inThe Mn-O-Mm bond angle.
Abstract: A detailed study of doped LaMn${\mathrm{O}}_{3}$ with fixed carrier concentration reveals a direct relationship between the Curie temperature ${T}_{c}$ and the average ionic radius of the La site $〈{r}_{A}〉$, which is varied by substituting different rare earth ions for La. With decreasing $〈{r}_{A}〉$, magnetic order and significant magnetoresistance occur at lower temperatures with increasing thermal hysteresis, and the magnitude of the magnetoresistance increases dramatically. These results show that the notion of ``double exchange'' must be generalized to include changes in the Mn-Mn electronic hopping parameter as a result of changes in the Mn-O-Mn bond angle.
1,654 citations
TL;DR: In this article, the relationship between crystallographic symmetry and superexchange interactions in perovskite systems has been investigated and it has been shown that the electron configuration that is used in the supeerexchange calculation must be correlated with the vibrational modes.
Abstract: An investigation has been made of the relationship between crystallographic symmetry and ${\mathrm{Mn}}^{3+}$ - ${\mathrm{O}}^{2\ensuremath{-}}$ - ${\mathrm{Mn}}^{3+}$ 180\ifmmode^\circ\else\textdegree\fi{} superexchange interactions in several perovskite systems. In particular, crystallographic and magnetic measurements have been made on a number of samples in the systems $\mathrm{La}({\mathrm{Mn}}_{1\ensuremath{-}x}{M}_{x}){\mathrm{O}}_{3+\ensuremath{\delta}}$, where $M=\mathrm{G}\mathrm{a},\phantom{\rule{0ex}{0ex}}\mathrm{C}\mathrm{o},\phantom{\rule{0ex}{0ex}}\mathrm{N}\mathrm{i}$. In all three systems, the ${\mathrm{Mn}}^{3+}$ - ${\mathrm{O}}^{2\ensuremath{-}}$ - ${\mathrm{Mn}}^{3+}$ interactions are found to be ferromagnetic for $O$-orthorhombic samples having $al\frac{c}{\sqrt{2}}lb$. For $xl0.5$ in the system $M=\mathrm{Ga}$, there is ${O}^{\ensuremath{'}}$-orthorhombic symmetry ($\frac{c}{\sqrt{2}}lalb$) and ferrimagnetism that is suggestive of anisotropic ${\mathrm{Mn}}^{3+}$ - ${\mathrm{O}}^{2\ensuremath{-}}$ - ${\mathrm{Mn}}^{3+}$ interactions, similar to those found in LaMn${\mathrm{O}}_{3}$, and preferential ordering of the ${\mathrm{Ga}}^{3+}$ into one magnetic sublattice. Measurements of Curie temperature vs composition in this system support ordering of the gallium in the compositional range $x\ensuremath{\le}0.4$, partial ordering in the range $0.4lx\ensuremath{\le}0.6$. These observations are consistent with the magnetic measurements of various other workers on the systems $(\mathrm{La}, {M}^{\ensuremath{'}2+})\mathrm{Mn}{\mathrm{O}}_{3+\ensuremath{\delta}}$, La(Mn,Cr)${\mathrm{O}}_{3}$ (La,Ba) (Mn,Ti)${\mathrm{O}}_{3}$.The ferromagnetic ${\mathrm{Mn}}^{3+}$ - anion - ${\mathrm{Mn}}^{3+}$ interactions that occur in the perovskites with $O$-orthorhombic or rhombohedral symmetry and in the NiAs-type compounds cannot be accounted for by present superexchange theory if the electron configuration about a ${\mathrm{Mn}}^{3+}$ ion is assumed fixed with one electron arithmetically averaged over the two ${e}_{g}$ orbitals, or if static, local distortions are randomly distributed through the structure. It is pointed out that Jahn-Teller electronic ordering is fast relative to the atomic vibrations so that there is strong coupling of the vibrational modes and the ${e}_{g}$-electron configuration. This means that the electron configuration that is used in the superexchange calculation must be correlated with the vibrational modes. If this is done, a ferromagnetic ${\mathrm{Mn}}^{3+}$ - anion - ${\mathrm{Mn}}^{3+}$ interaction follows from the superexchange theory.
567 citations