Substitution Of Nonmagnetic Ions Research Articles

Rare Earth Based Iron Garnet – A Survey on Its Magnetic Properties

Garnet is a well-known material for a long-time by the scientific community but still today scientists are focusing on it due to the rapid application-based development of this material. When rare earth iron garnets (REIG) are formed by substituting the rare-earth ions with unfilled 4fn orbitals, the magnetic properties of the iron garnets exhibit an interesting characteristic. For rare earth elements, the 4f electrons are shielded from the crystal field as these are surrounded by 5s, 5p, or 5d orbitals. That is why the exchange field between rare earth ions is much smaller than that between iron-iron and rare earth-iron. The magnetic moment of REIG will be both due to the orbital and spin moment. The magnetization of REIG at different temperatures (T) is due to the dominant contribution of different sublattices. At high and low T, the dominant sublattices are iron and rare earth sublattices respectively. The magnetic and non-magnetic ion substitution in REIG also play a very important role in deciding their magnetic property. In this review, we have tried to figure out the basic underlying physics behind the origin of remarkable magnetic behavior in REIG.

The role of Zn and Ru substitution on the structural, magnetic and dielectric properties of ferrite cuprospinels

A comprehensive study on the structural, magnetic and dielectric behavior of ferrite cuprospinels with site specific substitution of non-magnetic Zn and weakly magnetic Ru ions has been presented. Such substitution leads to two classes of stable crystal symmetries, (i) tetragonal (I41/amd): CuFe1.95Ru0.05O4 and Cu0.95Zn0.05Fe1.95Ru0.05O4 and (ii) cubic (Fd-3m):Cu0.60Zn0.40Fe1.95Ru0.05O4 and Cu0.05Zn0.95Fe1.95Ru0.05O4 bulk polycrystals. The former set of compounds undergo significant Jahn-Teller (JT) distortion due to high Cu content and such distortion gets lifted with the substitution of non-magnetic Zn ions. Ferrimagnetic (FiM) behavior is predominant in all these compounds except the highest Zn (95 at.%) content cubic system with diluted substitution of Ru (2.5 at.%) which exhibits antiferromagnetic ordering below the Néel temperature (T N ∼ 10.9 K). We employed Néel’s expression for FiM systems applicable for the two sublattice model to extract the dominant exchange interactions (J AA , J AB and J BB ) between the A-site and B-site cations. Subsequently the high temperature (300 K T 900 K) inverse paramagnetic susceptibility data has been fitted to the above expression which yields dominant ∼ 391 K with very high asymptotic Curie temperature for the tetragonally distorted dilute Zn substituted cuprospinel, while the Zn-rich cubic system exhibits ∼ 300 K. On the other hand, the tetragonally distorted spinel devoid of Zn exhibits dominant ∼ 229 K with negligible and moderate (65 K) signifying that the JT active ions cause the onset of magnetic frustration and enhanced ordering temperatures. All the investigated systems exhibit significant magneto-crystalline anisotropy with a maximum anisotropy field H K ∼ 6 kOe and maximum anisotropy constant (K 1 ∼ 10.88×105 erg cm−3). The broadband dielectric spectroscopy studies reveal significant enhancement of mid-frequency dielectric constant ε R (f, T) with plateau-like feature over a wide temperature and frequency window, together with low-loss as a result of the incorporation of Ru ions into the tetragonally distorted spinel lattice. The ac resistivity ρ(f, T) studies reveal that the mode of conduction follows Mott’s variable-range hopping (VRH) model with a linear logarithmic variation of ρ ac versus T −0.25. The temperature dependence of the VRH activation energy of charge carriers follows a linear behavior which indicates the presence of localized polaron in all the investigated systems.

High performance of Co-free LiNixMn1-xO2 cathodes realized by nonmagnetic ion substitution for Li-ion batteries

Ni-rich LiNixMn1-xO2 cathodes have been extensively probed to resolve the electrochemical performance degradation in the absence of Co3+ compared to LiNixCoyMn1-x-yO2 cathodes for lithium-ion batteries. Herein, LiNi0.6Mn0.4O2 (NM64) and a series of nonmagnetic Al3+ ions substituted NM64 cathode materials are designed and prepared via a sol–gel route. It is found that the inferior electrochemical performance of NM64 derives from the magnetic frustration arising from Mn ions and the unstable Mn3+ ions, which will lead to severe Li/Ni mixing, and weak structural and interfacial stabilities of the cathode. The superconducting quantum interference device (SQUID) analysis proves that the nonmagnetic Al3+ ion can lower the Li/Ni disorder in NM64 cathode by relieving magnetic frustration. Moreover, the dQ/dV and XPS analyses confirm that both structural and interfacial stabilities are enhanced for NM64 cathode owing to Al3+ substitution, contributing to fewer byproducts after a long cycle. Consequently, LiNi0.582Mn0.388Al0.03O2 cathode delivers a high discharging capacity of 179 mAh g−1 at 1.0C with a capacity retention of 87.6% after 100 cycles. This study not only gives an in-depth understanding of the mechanism of electrochemical performance degradation for NM64 cathode, but also demonstrates an efficient solving approach through Al3+ complementary substitution.

Development of In-Gap State and Related Collapse of Two-Step Energy Gap Structure by Nonmagnetic Ion Substitution in Kondo Insulator YbB12

YbB12, which has attracted attention as an unconventional strongly correlated insulator, has a two-step energy gap structure (\(\Delta E_{1},\Delta E_{2}\)) with an in-gap state. These characterist...

Nontrivial Spin Dimer in the Hexagonal Ruthenate Ba3CaRu2O9 Revealed by Nonmagnetic Ion Substitution

We have prepared a set of polycrystalline samples of Ba3Ca(Ru1−xNbx)2O9 consisting of the face-shared (Ru,Nb)2O9 dimer block from x = 0 to 0.12, and have measured the x-ray diffraction and magnetiz...

Mossbauer studies of Zn-substituted BiFeO3 multiferroic

This work presents an elaborate study of the effect in the structural and magnetic of [Formula: see text] ([Formula: see text], 0.05, 0.10, 0.15, 0.20, 0.25) multiferroic materials, synthesized via a sol-gel auto-combustion method. The synthesized materials are found to have structural distortion in the rhombohedral R3c structure as observed by X-ray diffraction (XRD). Other diffraction peaks were attributed to the second phase [Formula: see text]. The Mossbauer spectra (MS) of [Formula: see text] ([Formula: see text], 0.05, 0.10, 0.15) are fitted with a sextet and a doublet, and the presence of doublet also indicates the [Formula: see text] phase. The results from XRD and MS both show that Zn-substituted BiFeO3 suffers adverse effects on the formation of pure BiFeO3. [Formula: see text] ([Formula: see text], 0.25) are fitted with only one paramagnetic doublet. The absence of sextet means that there is a magnetic destruction of samples on account of a thorough phase transition from a magnetic phase to a non-magnetic phase and/or successful ion substitution (iron ions were replaced with zinc ions).

Enhanced room‐temperature magnetoelectric coupling effects in c‐axis oriented polycrystalline BaSrCo2‐xMgxFe11AlO22

AbstractThe influence of applied magnetic field during annealing process as well as of Mg doping on the room‐temperature magnetoelectric coupling effects in BaSrCo2‐xMgxFe11AlO22 are experimentally studied through the magnetization, magnetodielectric, and magnetoelectric current measurements. Hexaferrite samples of Co2Y were found to be highly oriented by an applied magnetic field (Ho) during the annealing process, leading to an enhancement of the room‐temperature magnetoelectric coupling effects. Although the substitution of nonmagnetic Mg ions in Co sites tends to reduce the ferromagnetism at macroscopic scale, a proper amount of Mg doping content facilitates the superexchange interaction between the adjacent magnetic blocks; meanwhile modulates the magnetic anisotropy in the samples. An appropriate adjustment of the competition between the anisotropy and the superexchange could enhance the magnetoelectric coupling at room temperature, which can be confirmed by the magnetic‐field‐induced dielectric constant and current density study.

Influence of Zn-Zr substitution on the crystal chemistry and magnetic properties of CoFe2O4 nanoparticles synthesized by sol-gel method

The Zn-Zr co-substituted cobalt ferrite nanoparticles (CoZnxZrxFe2-2xO4, x = 0.0˗0.4) were synthesized by sol gel auto combustion route. The formation of cubic phase of Co ferrite was revealed from the X-ray diffractograms of the powder samples. The additional α-Fe2O3 and ZrO2 phases were occurred for ≥20% Zn-Zr substitution. The lattice parameters obtained by extrapolating Nelson–Riley function shows increase in its values with the Zn-Zr substitution. The particle size shows increasing trend with the Zn-Zr substitution. The cation distribution obtained from the Rietveld refinement of XRD estimate the equal preference of Zn ons preferred tetrahedral A site whereas most of the Zr ions occupy octahedral B site. The decrease in Fe ions with the Zn-Zr substitution resulted in the decrease in coercivity and saturation magnetization of the ferrites. Zero field cooled and field cooled magnetization plots of the ferrites reveals the ferromagnetic behaviour of the prepared ferrite samples. The blocking temperature does not vary significantly with the varying Zn-Zr substitution. The Mössbauer study confirms the weakening of the magnetic linkages between cations at A and B sites, due to the substitution of non-magnetic Zn-Zr ions for magnetic Fe ions. The decrease in coercivity with moderate saturation magnetization could make this material suitable for electronic devices.

A comparative study of the effect of the non-magnetic and magnetic trivalent rare-earth ion substitutions on bismuth ferrite properties: Correlation between the crystal structure and physical properties

In this paper, the effect of the non-magnetic and magnetic trivalent ion substitutions on structure features and magnetic properties of Bi1-x(Gd or Y)xFe0.95Mn0.05O3 (x = 0.00, 0.01, 0.02, 0.03) nanoparticles have been investigated. The prepared samples were analyzed using the techniques of X-ray diffraction, vibrating sample magnetometer, and scanning electron microscopy (SEM) measurements. Structural analysis of Bi1-x(Gd or Y)xFe0.95Mn0.05O3 nanoparticles shows that a phase transition from rhombohedral (space group R3c) to cubic (space group Pm3¯m) occurs at x=0.02. SEM images show the average particle size of 50–100 nm which decreases with increasing the Gd/Y concentration. The magnetic properties of Gd- and Y-substituted samples such as the coercive field (HC), remanent magnetization (Mr) and saturation magnetization (Ms) indicate a ferrimagnetic behavior compared to the antiferromagnetic behavior of samples BiFeO3 and BiFe0.95Mn0.05O3. The observed magnetic behavior has been attributed to the observed structural phase transition and the reduction of particle size with the substitution of Gd3+ and Y3+ ions.

Effects of In3+ site occupancy on the magnetic properties of M-type strontium hexaferrites

Effects of nonmagnetic indium ion substitution on magnetic properties of M-type strontium hexaferrites SrFe12-xInxO19 (x=0, 0.25, 0.5, 0.75, and 1) have been studied by crystallographic and magnetic measurements. Samples were prepared by citric auto-combustion method. Rietveld analysis of X-ray diffraction profiles showed that the samples were single phase with the space group P63/mmc and lattice constants a and c increased linearly with In3+ content. Mössbauer spectra showed that In3+ mainly replaced Fe3+ ions in 4f2 sites and that 12k subspectra split into two distinct components 12k1 and 12k2. Analysis of hysteresis curves showed that while the coercive force and the magnetic anisotropy constant decreased thru the whole doping range x, the saturation magnetization first increased until x=0.5 and decreased thereafter. This behavior was explained by the existence of two competing interactions in terms of nonmagnetic indium substitution.

Room temperature and low-field resonant enhancement of spin Seebeck effect in partially compensated magnets

Resonant enhancement of spin Seebeck effect (SSE) due to phonons was recently discovered in Y{}_{3}Fe{}_{5}O{}_{12} (YIG). This effect is explained by hybridization between the magnon and phonon dispersions. However, this effect was observed at low temperatures and high magnetic fields, limiting the scope for applications. Here we report observation of phonon-resonant enhancement of SSE at room temperature and low magnetic field. We observe in Lu{}_{2}BiFe{}_{4}GaO{}_{12} an enhancement 700% greater than that in a YIG film and at very low magnetic fields around 10{}^{-1} T, almost one order of magnitude lower than that of YIG. The result can be explained by the change in the magnon dispersion induced by magnetic compensation due to the presence of non-magnetic ion substitutions. Our study provides a way to tune the magnon response in a crystal by chemical doping, with potential applications for spintronic devices.

Intrinsic Magnetic and Ferroelectric Behaviour of Non-magnetic Al3+ Ion Substituted Dysprosium Iron Garnet Compounds

Synthetic garnets are a group of oxide materials that play a vital role in the development of solid state lasers, magnetic and optic-electronic devices. The analysis on the solubility of rare-earth elements in the well-crystallized system has led to the discovery of peculiar oxide materials with multifunctional properties. By following the above importance, Aluminium ion (Al3+) substituted Dysprosium Iron Garnet compounds with the chemical formula of Dy3Fe5−xAlxO12 (x = 0–0.5) have been synthesized by the solid state reaction method and the effect of substitution of non-magnetic ions into the magnetic sub-lattices have been analyzed. The Rietveld refinement of powder x-ray diffraction patterns confirms that the pure Dy3Fe5O12 compound crystallizes with cubic (Space group: Ia3d) superstructure whereas all the Al3+ substituted samples exhibit the coexistence of cubic (Ia3d) and trigonal Fe2O3 (R3c) phases. The energy gap values of the prepared compounds is found to be around 1.6 eV which reveals the semiconducting nature and the decreasing trend of band gap values may be due to the growth factor of crystallites, structural disorder and distortion introduced into the crystal lattice. From the Micro-Raman analysis, it is found that the substituted Al3+ ions starts filling into both tetrahedral and octahedral positions and the assignments of vibrational modes observed from Raman spectra confirm the incorporation of Al3+ ions into the Dy3Fe5O12 garnet structure. From the magnetization analysis, it is found that the response of super-exchange interaction between Fe3+ ions in the a and d sites of Dy3Fe5O12 compound leads to net magnetic moment and the substitution of Al3+ ions preferably replaces Fe3+ ions in d sites and suggests the decrease in net magnetization values. From the photoluminescence studies, it is noticed that the luminescence behavior of Al3+ ions substituted Dy3Fe5−xAlxO12 compounds are due to the superposition of a broad emission band and reveals the variation in concentration of Al3+ ions in the prepared compounds. An interesting point to note is that, a well saturated “soft” ferroelectric hysteresis loop is obtained in both pure and Al3+ substituted Dy3Fe5−xAlxO12 compounds, and the observed electric hysteresis loops are found to be influenced by the factors such as capacitance nature, resistivity effects and leakage current of the compounds. Hence, the study on effect of trivalent non-magnetic ion substitution in a hard magnetic Dy3Fe5O12 system leads to interesting intrinsic magnetic and ferroelectric properties and found suitability for the fabrication of energy storage and optoelectronic devices.

Magnetic Structure of Diluted Iron Garnets

The report presents a model of the magnetic structure of diluted iron garnets with nonmagnetic ions in a dodecahedral sublattice. The dilution of magnetic iron sublattices is assumed to be selective: in the limiting case, the substitution of nonmagnetic ions for iron takes place only in a tetrahedral sublattice. In this case, iron ions in the octahedral environment have a variable number of the nearest magnetic neighbors; thus, octahedral sublattice are introduced in the dependence on the number of magnetic neighbors. This model is shown to describe well the magnetic properties of diluted iron garnets with a compensation point.

Ferroelectricity in the multiferroic delafossite CuFeO2 induced by ion doping or magnetic field

On the basis of a microscopic model and using the Green's function technique we have studied the induced ferroelectric polarization P[110] along the [110] direction in the triangular CuFeO2. It is shown that P[110] is induced by an external magnetic field parallel to the c axis hc or a nonmagnetic ion substitution which both can break the inversion symmetry of the system. Our Hamiltonian consists of Heisenberg antiferromagnetic interactions in and out of the ab plane and anharmonic spin-phonon interactions. P[110] decreases with increasing the temperature T. It appears at T ∼ 9 K and begins to increase below T ∼ 9 K, which is the transition temperature to a noncollinear phase. This behavior is an evidence for the multiferroic character of CuFeO2. By doping with Rh ions the polarization has a maximum in the curve P[110](x) with increasing Rh concentration x whereas by Sc doping it decreases. The observed results are in qualitative agreement with the experimental data.

Role of Gallium in the charge transport mechanisms for La0.67Ca0.33Mn1–xGaxO3 manganites

In this communication, we report the results of the studies on structural, transport and magnetoresistance (MR) properties of nonmagnetic Ga – substituted La0.67Ca0.33Mn1–xGaxO3 (LCMGO) manganites synthesized using conventional ceramic route. Rietveld refined XRD patterns shows that all the samples possess single phasic nature without any detectable impurity. Resistivity behavior shows a systematic variation with Ga3+ – content (x) while metal to insulator transition temperature (TP) shifts towards lower temperature which has been discussed in the light of zener double exchange (ZDE) mechanism and magnetic lattice distortion due to nonmagnetic ion substitution. Observation of low temperature resistivity minima behavior has been explained in the context of electron – electron scattering mechanism. Various transport models and mechanisms have been employed to understand the charge transport in metallic and semiconducting regions of all LCMGO samples. Temperature and Field dependent MR studies reveal intrinsic and extrinsic MR contributions in presently studied LCMGO manganites.

Enhanced magnetism of perovskite oxides, Sr(Sn,Fe)O3-δ , by substitution of nonmagnetic Ca and Ti ions

Magnetic properties of perovskite oxides, SrSn1-x Fe x O3-δ (x ≤ 0.15), substituted with nonmagnetic Ca and Ti ions were studied. XRD patterns showed the orthorhombic structure (close to tetragonal) of (Sr1-y Ca y )(Sn1-x Fe x )O3-δ and Sr(Sn1-x-y Fe x Ti y )O3-δ . The cell volumes decreased with the increase of Ca and Ti doping rates. Although Ti-substituted Sr(Sn, Fe)O3-δ showed small saturation magnetizations as compared with non-Ti substituted one, the magnetization increased a little with Ti doping rates up to 15%. On the other hand, all Ca-substituted Sr(Sn, Fe)O3-δ showed larger saturation magnetization than non-Ca substituted one. Two doublets of Fe3+ and a doublet of Fe4+ were observed in Mossbauer spectra of Ca-substituted Sr(Sn, Fe)O3-δ with weak ferromagnetism, and two sextets of high spin Fe3+ were additionally observed in Mossbauer spectra of Ca-doped Sr(Sn, Fe)O3-δ with relatively strong ferromagnetism. When Sr(Sn, Fe)O3-δ were further codoped with Ca and Ti ions, they showed the stable and enhanced ferromagnetic properties. It is considered that magnetic polarons among high spin Fe3+ species are overlapped by shrinking or deforming the crystal structure of perovskite oxides. That is the magnetism induced by a chemical pressure of perovskite oxides.

Study of the Effects of A‐Site La‐Substition on the Electrical and Magnetic Properties of Dy0.5Sr0.5MnO3 Ceramics

The Dy0.5−xLaxSr0.5MnO3 (0 ≤ x ≤ 0.4) manganite compounds have been synthesized by solid state reaction, and the effect of nonmagnetic La ion doping on the crystal structure, electrical and magnetic properties are systematically investigated. It is found that with successive substitution of La element, A‐site cationic arrangement transforms from disorder (random, x ≤ 0.25) to order structure (x > 0.25), and the crystal structure undergoes a transition from cubic to orthogonal distorted perovskite structure. When 0 ≤ x < 0.25, the compounds show a similar semiconducting behavior and magnetic property with a low‐temperature spin‐glass state. When x = 0.25, however, long‐range ferromagnetic (FM) order begins to form and coexists with anti‐ferromagnetic (AFM) phase in the compound. When x further increases, FM interactions strengthen and become predominant in the magnetic properties of the compound. On the other hand, in contrast to the semiconducting behavior of the compounds with x ≤ 0.25, when x > 0.25, the resistivity decreases quickly in the corresponding temperature range. It is suggested that not only the A‐site cationic disorder turning, closely related to the cation radius distribution (mismatch), σ2, controlled by A‐site cation radius 〈rA〉, but the substitution of nonmagnetic La ions, or A‐site magnetic change, is an effective way to adjust the crystal structure and the related magnetic and electrical properties of the perovskite manganite oxides for the applications.

Effect of non-magnetic and magnetic trivalent ion substitutions on BaM-ferrite properties synthesized by hydrothermal method

Two species trivalent transition metal ions, nonmagnetic Al3+, Bi3+ and magnetic Cr3+, Mn3+ substituted barium hexaferrite powders are synthesised via dynamic hydrothermal method then calcinated at different temperatures. Powder XRD patterns analysis and Rietveld refinement indicate magnetoplumbite-type crystalline phase. The crystallite size calculated using Scherer's formula varies from 153 to 248 nm as it is affected by the ionic radius of trivalent metal ions and calcination temperatures. The morphological features show agglomerations of spherical-shaped particles with an average size of 400 ± 50 nm for BaBiFe11O19 and hexagonal-shaped particles 1–2 μm for the other substitutions. Magnetic studies show a ferromagnetic behaviour for all samples. The nonmagnetic Al3+, Bi3+ substituted materials have lower saturation magnetization (Ms) and remanence (Mr) than the magnetic substitutions Cr3+, Mn3+. These results reveal that Ms and Mr are related to the magnetic moment of each metallic ion and its distribution in the lattice. For magnetic substitution, Ms of manganese substitution (61.10 emu/g) is found higher than that of chromium (60.33 emu/g) since Mn3+ has a magnetic moment of 5μB greater than Cr3+ with 3μB. Coercivity Hc and maximum energy product (BH)max determined from M−H loops exhibit an increasing trend with calcination temperature as they are related to the crystallite size. Hc and (BH)max of BaMnFe11O19 are found maximum 0.426 T and 7.47 kJ m−3, respectively.

Magnetic versus nonmagnetic ion substitution effects in gapless semiconductor PbPdO2

PbPdO2 is a gapless semiconductor, of which the physical properties are easily tuned by external parameters such as temperature, magnetic field, and chemical doping. We have studied the physical properties tuned by magnetic and nonmagnetic ion substitutions. When Pd in PbPdO2 is substituted by Zn, that is, divalent and nonmagnetic with 3d10 (S = 0), the electrical resistivity decreases and the magnetic properties are not changed to remain diamagnetic. However, by substituting Cu2+ (3d9) with S = 1/2, the electrical resistivity increases and the magnetization shows paramagnetic behavior. Another noticeable feature in the magnetic versus nonmagnetic ion substitution is found in the magneto-transport data. The magnetoresistance for PbPd0.9Cu0.1O2 is positive, compared with the negative behavior for PbPd0.9Zn0.1O2. These results propose that chemical dopants play an important role in optimizing the tunability of the physical properties of gapless semiconductors.

Non-uniform Magnetic System Driven by Non-magnetic Ion Substitution in CaRu1−xScxO3: Two-Component Analysis

We have studied magnetic and transport properties in polycrystalline CaRu1-xScxO3 for 0 =< x =< 0.20 in order to clarify the substitution effects of a non-magnetic trivalent ion. We find that a ferromagnetic transition with Tc = 30 K is observed in Sc-substituted samples. The composition dependence of the Curie-Weiss temperature implies that the magnetic susceptibility has a paramagnetic contribution with negative theta and a ferromagnetic contribution with positive theta. The field dependence of magnetization at 2 K is also understood as a summation of the ferromagnetic and paramagnetic components. These results suggest that CaRu1-xScxO3 is a non-uniform magnetic system. The relationship between the ferromagnetic ordering and the transport properties is also discussed.