Octahedral B-site Research Articles

Charge ordering in reactive sputtered (1 0 0) and (1 1 1) oriented epitaxial Fe3O4 films

Epitaxial Fe 3 O 4 films with (1 0 0) and (1 1 1) orientations fabricated by reactive sputtering present simultaneous magnetic and electrical transitions at 120 and 124 K, respectively. The symmetry decreases from face-centered cubic to monoclinic structure across the Verwey transition. Extra spots with different brightness at different positions appear in selected-area diffraction patterns at 95 K. The extra spots come from the charge ordering of outer-layer electrons of Fe atoms, and should be related to the charge ordering of octahedral B-site Fe atoms.

Cation distribution and Mössbauer spectral studies of Mg0.2Mn0.5Ni0.3InxFe2−xO4 ferrites (x = 0.0, 0.05 and 0.10)

The effect of substitution of diamagnetic indium ions in Mg–Mn–Ni ferrite with the composition Mg0.2Mn0.5Ni0.3InxFe2−xO4 (x=0.0, 0.05 and 0.10) synthesized by citrate precursor technique has been investigated. Crystallographic and magnetic properties have been investigated using X-ray diffraction, TEM, VSM and Mössbauer spectroscopy. The single phase cubic spinel structure of these samples has been confirmed from X-ray diffraction analyses. In3+ ions initially prefer tetrahedral A-site up to x=0.05 due to which saturation magnetization and magnetic moment increases, followed by subsequent decrease when indium ions begin to occupy octahedral B-site for higher concentration of x. Magnetization measurements exhibit Neel’s collinear ferrimagnetic structure for samples up to x=0.05. Mössbauer spectra of these samples studied at 300K show two characteristic ferrimagnetic Zeeman sextets for x=0.0, followed by relaxation phenomenon corresponding to x=0.05 and 0.10. Mössbauer measurements also show dependence of Zeeman spectral lines on smaller particle size which is indicative of their superparamagnetic nature. The dependence of Mössbauer parameters such as isomer shift, quadrupole splitting, linewidth and hyperfine magnetic field on In3+ ions concentration have been discussed. The variation of hyperfine magnetic field with increasing In3+ ions content has been explained by Neel’s molecular field theory.

Mn3+ substituted Co–Cd ferrites, CoCd0.4MnxFe1.6−xO4 (0.1 ⩽ x ⩽ 0.6): Cation distribution, structural, magnetic and electrical properties

The substitution of Mn3+ ions in cobalt–cadmium ferrites (synthesized via sol–gel auto-combustion method) is found to remarkably influence their structural, magnetic and electrical properties. The structural evolutions of the nanophase, investigated using powder X-ray diffraction (XRD) studies reveal the formation of single-phased cubic spinel structures, with Fd-3m space group. As the Mn3+ concentration is increased, the values of the structural parameters like lattice constant, crystallite size, X-ray density, bulk density and porosity undergo significant changes. The value of lattice constant is found to be ∼8.40Å and the average crystallite size is in the range of 41–45nm. The porosity in the entire ferrite samples is low (4.0–10.2%). The magnetic properties, like saturation magnetization and coercivity, show a decreasing trend with increase in Mn3+ concentration. Using the values of saturation magnetization, the cation distribution has been proposed. The proposed cation distribution is further correlated with the electrical properties. It is observed that the D.C. resistivity increases with Mn3+ concentration, suggesting occupancy of Mn3+ ions in the octahedral B-sites which leads to the dilution of Fe2+–Fe3+ conduction. The activation energy calculated from the D.C. resistivity vs temperature curves is found to be ∼0.50eV.

Effect of neodymium substitution on structural and magnetic properties of magnesium ferrite nanoparticles

The effect of Nd3+ substitution on the structural properties of magnesium ferrite prepared by the sol–gel technique was studied in the series MgNdxFe2−xO4, where x = 0–0.3 in steps of 0.05. X-ray diffraction analysis revealed the limit for Nd3+ doping without any secondary phase appearing along with the spinel phase. Particle size calculation shows that the crystallite sizes of the prepared samples are in the 21–30 nm regime. The decrease in value of the lattice parameter with doping suggests that the shrinkage in unit cell and the crystallite size increase with Nd3+ concentration. Fourier transform infrared analysis shows that the substitution of Fe3+ ions is in octahedral B-sites by Nd3+ ions. X-ray fluorescence results show that the composition of prepared samples is in the expected ratio. Transmission electron microscope micrographs revealed spherical morphology and magnetic interaction of the samples. Magnetic measurements revealed the B-site substitution of Nd3+ ions in the series MgNdxFe2−xO4. The variation of magnetic parameters with doping concentration is explained with the help of particle size dependence.

Structural and magnetic characterization of Co2+ substituted nano structured Copper-Zinc spinel ferrite

Nano particles of Cu0.61-xCoxZn0.39Fe2O4 (0 ≤ x ≤ 0.5) synthesized through sol-gel auto combustion method. Nitrates of elements and citric acid are used as starting materials. X-ray Diffraction, Thermo Gravimetric Analysis and Vibrating Sample Magnetometer are used to analyze the properties. Effect of variation in the Co substitution and its impact on particle size, lattice constant, density, cation distribution, ferritization temperature, associated water content, magnetic properties like saturation magnetization(MS), coercivity(HC) and remanent magnetization(Mr) is observed. Lattice parameter increases with increasing Co +2 concentration whereas X-ray density, bulk density decreases with the Co +2 content. In Cation distribution the Co and Cu ion show preference towards octahedral B-site, Zn occupy A site whereas Fe occupy both A and B site. Cation redistribution takes place for x > 0.3. Saturation magnetization increases from (x ≤ 0.3). For x > 0.3, Ms decreases suggesting that significant canting exists at B site. However, coercivity, magnetocrystalline anisotropy and remanant magnetization increases with the Co 2+ substitution.

Low temperature synthesis of Li0.5ZrxCoxFe2.5−2xO4 powder and their characterizations

Lithium–zirconium–cobalt ferrites bearing the chemical formula Li0.5ZrxCoxFe2.5 − 2xO4 for x ranging from 0.0 to 0.5 with the step increment of 0.1 were synthesized by the sol–gel auto combustion technique. The variation of ZrCo substitution has a significant effect on the structural, electrical and magnetic properties of lithium ferrite. Lattice parameters ‘a’ increased from 8.331 to 8.358 Å. Cation distribution data suggest that Co2 + and Li+ show marked preference for octahedral B-site, whereas Zr4 + and Fe3 + occupy both the available sites. The IR spectra show two major absorption bands related to the spinel structure of ferrite. Saturation magnetization decreased whereas coercivity increased with the increase in ZrCo substitution. Resistivity and activation energy increased whereas dielectric constant decreased with the increase in ZrCo substitution. Dielectric constant increased with the increase in temperature from 403 to 773 K at a constant frequency of 1 kHz. The possible reasons responsible for the changes in structural, electrical and magnetic properties with the increase in ZrCo substitution are undertaken.

Co-doping of (Bi0.5Na0.5)TiO3: secondary phase formation and lattice site preference of Co

Bismuth sodium titanate (Bi0.5Na0.5)TiO3 (BNT) is considered to be one of the most promising lead-free alternatives to piezoelectric lead zirconate titanate (PZT). However, the effect of dopants on the material has so far received little attention from an atomic point of view. In this study we investigated the effects of cobalt-doping on the formation of additional phases and determined the preferred lattice site of cobalt in BNT. The latter was achieved by comparing the measured x-ray absorption near-edge structure (XANES) spectra to numerically calculated spectra of cobalt on various lattice sites in BNT. (Bi0.5Na0.5)TiO3 + x mol% Co (x = 0.0, 0.5, 1.0, 2.6) was synthesized via solid state reaction. As revealed by SEM backscattering images, a secondary phase formed in all doped specimens. Using both XRD and SEM-EDX, it was identified as Co2TiO4 for dopant levels >0.5 mol%. In addition, a certain amount of cobalt was incorporated into BNT, as shown by electron probe microanalysis. This amount increased with increasing dopant levels, suggesting that an equilibrium forms together with the secondary phase. The XANES experiments revealed that cobalt occupies the octahedral B-site in the BNT perovskite lattice, substituting Ti and promoting the formation of oxygen vacancies in the material.

Substitutional effect of Cr3+ ions on the properties of Mg–Zn ferrite nanoparticles

The effect of Cr 3+ substitution in Mg–Zn ferrite, with a chemical formula Mg 0.5 Zn 0.5 Cr x Fe 2− x O 4 ( x =0.0–1.0), synthesized by a sol–gel auto-combustion reaction is presented in this paper. The resultant powders were investigated by various techniques, including X-ray diffractometry (XRD), transmission electron microscopy (TEM), infrared spectroscopy (IR), vibrating sample magnetometry (VSM), and DC resistivity. The XRD pattern revealed that the cubic spinel structure is maintained for the all the compositions. The particle sizes measured from XRD and TEM are in good agreement with each other. The cation distribution suggests that Mg 2+ , Cr 3+ and Fe 3+ have strong preference towards octahedral B-site. The theoretical lattice constant and experimental lattice constant match each other very well. The IR analysis supports the presently accepted cation distribution. The saturation magnetization decreases linearly with increasing Cr 3+ content. Curie temperatures are obtained by the Laoria and AC susceptibility techniques. The dc resistivity has been investigated as a function of temperature and composition.

Characterization and Magnetic Properties of Nanoparticle Ni1−x Zn x Fe2O4 Ferrites Prepared Using Microwave Assisted Combustion Method

Nanoparticle Ni1−xZnx Fe2O4 (x=0.35,0.45) samples were prepared successfully via microwave assisted combustion method. Synthesis of nanosize materials at a low temperature using a domestic microwave oven is the unique feature of this method and is being tried for the first time to produce NiZn ferrites. Single-phase formation of the samples was confirmed from X-ray analysis and IR spectrum. XRD data reveals that lattice parameter increases with Zn content ‘x’. Particle sizes calculated from XRD analysis are in good agreement with TEM results. Extent of spin canting at octahedral B-site is deduced from Yafet–Kittel angles. Surface properties and reduced particle size affects the Curie temperature.

Raman study of cations’ distribution in Zn x Mg1−x Fe2O4 nanoparticles

In a complementary way, Raman and Mossbauer spectroscopy were successfully employed to assess the cations’ distribution among the tetrahedral (A-site) and octahedral (B-site) sites of nonosized Zn x Mg1−x Fe2O4 (0 ≤ x ≤ 1) cubic ferrite structure, synthesized by combustion reaction method. Nanoparticles with little change in size distributions, in the 40 nm (x = 0.0) up to 42 nm (x = 1.0) were obtained. Mossbauer data indicated that as the Zn-content (x) increases in the range 0 ≤ x ≤ 1, the Fe3+ ion monotonically increases (decreases) the A-site (B-site) occupancy up to nearly equal values at the highest end x value. Analysis of the Raman data, however, confirms that the three highest energy modes around 650, 668 and 710 cm−1 are assigned to Zn–O (B-site), Fe–O (A-site) and Mg–O (A-site) vibrations, respectively. Additionally, in agreement with the Mossbauer data, the Raman data show that as the Zn-content (x) increases in the range 0 ≤ x ≤ 1, the occupancy of A-sites by Mg2+ ions monotonically reduces with concomitant increase of A- and B-sites occupancy by Fe3+ and Zn2+ ions, respectively. Indeed, combination of the two sets of spectroscopic data (Raman and Mossbauer) provides an effective protocol for assessing the cations’ distribution within the crystal structure of nanosized quaternary cubic ferrite samples running for instance from \( \left[ {{\text{Fe}}_{0.42}^{3 + } {\text{Mg}}_{0.58}^{2 + } } \right]^{A} \left[ {{\text{Zn}}_{0.20}^{2 + } {\text{Mg}}_{0.22}^{2 + } {\text{Fe}}_{1.58}^{3 + } } \right]^{B} O_{4}^{2 - } \) at x = 0.2 up to \( \left[ {{\text{Fe}}_{1.0}^{3 + } } \right]^{A} \left[ {{\text{Zn}}_{0.60}^{2 + } {\text{Mg}}_{0.40}^{2 + } {\text{Fe}}_{1.0}^{3 + } } \right]^{B} {\text{O}}_{4}^{2 - } \) at x = 0.6.

Magnetic characteristics of a new cubic defect spinel Li0.5Mg0.5MnO3

Magnetic properties of Li0.5Mg0.5MnO3−δ nanoparticles (size ≃ 20 nm) synthesized by the Pechini method are investigated using temperature dependence of its magnetization (M) and electron magnetic resonance (EMR) spectra at 9.286 GHz. Analysis of the x-ray diffraction spectra yields its structure to be a cubic defect spinel with the formula 4(Li0.5Mg0.5MnO2.75) = 3{[Li2/3Mg1/3][Mn4/3Mg1/3□1/3]O11/3]} so that Mn occupies the octahedral B-sites only. The data of M versus T yields a blocking temperature TB ≃ 9 K above which the Curie–Weiss law variation with θ = 13 K and μ = 3.96μB characteristic of Mn4+ ions is established. For T < 9 K, temperature dependent coercivity and remanence are observed. The observed temperature dependence of the EMR parameters (linewidth ΔH, resonance field Hr, and intensity Io) for T < 30 K is interpreted in terms of TB (EMR) ≃ 30 K. Formation of ferromagnetic Mn4+ clusters, resulting from the co-presence of non-magnetic Mg2+ and vacancies on the B-sites, is inferred.

Cation Distribution Dependence on Thermoelectric Properties of Doped Spinel M<sub>0.6</sub>Fe<sub>2.4</sub>O<sub>4</sub>

The electrical conductivity, Seebeck coefficient, and thermal conductivity of polycrystalline M0.6Fe2.4O4 (M = Ni, Ni0.5Mg0.5, Ni0.5Zn0.5, Zn) were measured to elucidate cation distribution-dependent changes. Preferential occupation by the doped cation in the iron spinel has been noted: Zn2+ ions prefer to occupy the tetrahedral A-site, while Ni2+ and Mg2+ prefer to occupy the octahedral B-site. While the electrical conductivity and Seebeck coefficient are almost cation distribution-independent, the thermal conductivity at room temperature is sensitive to the cation distributions. The lowest thermal conductivity of 2.0Wm11 K11 at room temperature is observed for Zn0.6Fe2.4O4. The value is about one third of that of Ni0.6Fe2.4O4. The thermal transport of MxFe31xO4 is mainly affected by cation distribution at the A-site, while the electrical transport is affected by the B-site, which is discussed in terms of the point defects at the Aand B-sites. Due to the disordering at the Aand Bsites, the thermal conductivity of MxFe31xO4 could be reduced without decreasing the electrical conductivity. Doped spinel-ferrite MxFe31xO4 would be a kind of “phonon-glass electron-crystal” material. [doi:10.2320/matertrans.M2012023]

Effects of doping site and pre-sintering time on microstructure and magnetic properties of Fe-doped BaTiO 3 ceramics

The A-site substituted BaTiO 3 ceramics were prepared by solid-state reaction via partial substitution of Fe for Ba 2+. By comparison with the B-site substituted sample made under similar conditions, the effect of Fe doping site on microstructure and magnetism was investigated using X-ray diffraction, Mössbauer spectroscopy and vibrating sample magnetometer. It is found that A-site substitution can be realized to a certain extent at 7 at% Fe addition, whereas impurities are observed at higher Fe concentrations. In the nominal (Ba 0.93Fe 0.07)TiO 3 sample, the Fe ions are present as Fe 2+ and Fe 3+, respectively, replacing A-site Ba 2+ and octahedral B-site Ti 4+ in hexagonal perovskite lattice. The double-exchange Fe 2+–O 2−–Fe 3+ interactions produce ferromagnetism well above room temperature, but the saturation magnetization and the Curie temperature are both obviously lower than those for B-site substitution due to different magnetic exchange mechanisms. In the B-site substituted sample Ba(Ti 0.93Fe 0.07)O 3, the super-exchange interactions between Fe 3+ on pentahedral and octahedral Ti 4+ sites are responsible for ferromagnetism. These results mean that B-site substitution is a better way for Fe-doped BaTiO 3 system to obtain high-Curie-temperature ferromagnetism. Moreover, increasing pre-sintering time can further improve the magnetism of B-site substituted samples, through which the saturation magnetization for Ba(Ti 0.93Fe 0.07)O 3 is enhanced ∼6 times.

Formation, cationic site exchange and surface structure of mechanosynthesized EuCrO3 nanocrystalline particles

Nanocrystalline EuCrO3 particles (∼25 nm) have been prepared by pre-milling a 1 : 1 molar mixture of Eu2O3 and Cr2O3 for 60 h followed by sintering at 700 °C (12 h). This temperature is ∼500–600 °C lower than those at which the material, in bulk form, is conventionally prepared. Rietveld analysis of the x-ray powder diffraction pattern of the EuCrO3 nanoparticles favours a structural model involving a slight degree of cationic exchange where ∼11% of the Eu3+ and Cr3+ ions exchange their normal dodecahedral A- and octahedral B-sites, respectively, in the perovskite-related structure. This cationic site exchange, which is unusual in a perovskite structure, has been well supported by the corresponding room-temperature 151Eu Mössbauer spectrum of the nanoparticles that in addition to displaying a distribution in the principal component of the EFG tensor (Vzz) at the usual A-sites of the 151Eu nuclei, also revealed the presence of a subcomponent with ∼11% area fraction and a considerably increased |Vzz| value that was associated with Eu3+ ions at octahedral B-sites. X-ray photoelectron and Auger electron spectroscopic techniques reveal a complex surface structure where extremely thin layers of un-reacted Eu2O3 and Cr2O3 cover most of the EuCrO3 nanoparticles' surfaces together with some traces of elemental Cr. The binding energies associated with Eu3+ 3d5/2, Eu3+ 4d3/2, Cr3+ 2p3/2 and O2− 1s core-level electrons in EuCrO3 are estimated from the x-ray photoelectron data for the first time.

Freezing of polarization dynamics in relaxor ferroelectric (1− x)Pb(Mg 1/3Nb 2/3)O 3− xBi(Zn 1/2Ti 1/2)O 3 solid solution

Ceramics of a the binary solid solution (1− x)Pb(Mg 1/3Nb 2/3)O 3− xBi(Zn 1/2Ti 1/2)O 3 [(1− x)PMN− xBZT] have been prepared with x = 0.10 and 0.15 and examined by dielectric spectroscopy to reveal the temperature dependences of the relaxor ferroelectric behavior. Both compositions studied show a broad and diffuse peak in the temperature dependence of dielectric permittivity ɛ’( T), the temperature of which increases with increasing measurement frequency, indicating the typical relaxor behavior. Detailed analysis of the dielectric response shows that it involves the same types of polarization contributions as the prototypical relaxor Pb(Mg 1/3Nb 2/3)O 3. One of the contribution to the permittivity arises from the conventional relaxor polarization, χ C R ∗ , which can be described by the Kohlrausch–Williams–Watts (KWW) law, P ∝ exp [ − ( t / τ ) β ] . It is found that the β and τ parameters both follow the Vogel–Fulcher law, with the freezing temperature T f decreasing with increasing BZT content. The change in diffuseness and freezing temperature can be attributed to the increase in chemical disorder because the addition of BZT end member introduces two more heterovalent cations (Zn 2+ and Ti 4+) on the perovskite octahedral B-site and the Bi 3+ cations on the perovskite A-site of PMN.

Origin of the constricted hysteresis loop in cobalt ferrites revisited

A series of Co ferrites (Co x Fe 3− x O 4 ( x=0−1)) were prepared using solid-state method in this work. The aging effect of their structures and constrictions of hysteresis loops under low magnetic field were investigated. It was found that during the aging process, the migration of trivalent (bivalent) ions between tetrahedral (A-site) and octahedral (B-site) coordination induced a shrinking of the lattice, which would expand again due to the precipitation of Fe 3+ after a much longer aging time. The first process caused a pronounced constriction of the loops, due to the uniaxial anisotropy led by this migration. The depression of constriction could attribute to both the expansion of lattice and the change of ionic ratios as a result of the second-phase-precipitation. The impacts of Co content, aging time and temperature upon the constriction were also discussed.

Sol–gel synthesis of Cr 3+ substituted Li 0.5Fe 2.5O 4: Cation distribution, structural and magnetic properties

Li 0.5Cr x Fe 2.5− x O 4 powders with fine sized particles were successfully synthesized by sol–gel auto combustion, using lithium nitrate, ferric nitrate, chromium nitrate, and citric acid as the starting materials. The process takes only a few minutes to obtain as-prepared Cr-substituted lithium ferrite powders. The resultant powders were annealed at 600 °C for 4 h and investigated by thermogravimeter/differential thermal analyzer (TG/DTA), X-ray diffractometer (XRD) and vibrating sample magnetometer (VSM). Lattice parameter, bulk density and particle size are found to decrease with increasing Cr concentration, whereas X-ray density and porosity showed an increasing trend with the Cr content. Cation distribution indicates that the chromium ion occupy octahedral B-site. The magnetic moments calculated from Neel's molecular field model are in agreement in the experiment result, which indicates that the saturation magnetization decreases linearly from 37.36 to 4.27 emu/g with increasing Cr 3+ content. However, coercivity, it increases with the Cr 3+ substitution.

Spectral studies of Co substituted Ni–Zn ferrites

The spinel ferrites Zn 0.35Ni 0.65− x Co x Fe 2O 4, 0≤ x≤1, have been prepared using the standard ceramic technique. Room temperature Mössbauer, X-ray and infrared IR spectra were used for carrying out this study. X-ray patterns reveal that all the samples have single-phase cubic spinel structure. The Mössbauer spectra of the samples show a paramagnetic phase for x=0 and a six-line magnetic pattern and a central paramagnetic phase for x≥0.1. They are analyzed and attributed to two magnetic subpatterns and two quadrupole doublets due to Fe 3+ ions at the tetrahedral A-sites and octahedral B-sites. Four absorption bands are observed in IR spectra. They confirm the spinel structure of the samples and existence of Fe 3+ ions in the sample sublattices. The deduced hyperfine interactions, lattice parameters, absorption band positions and intensities and force constant are found to be dependent on the substitution factor x, where the cation distribution is estimated. The hyperfine magnetic fields, magnetization and lattice resonant frequency are found to be dependent on the interionic distance.

Structure, electric and dielectric studies of indium-substituted magnesium copper manganese ferrites

The structure, electric and dielectric properties of In-substituted Mg–Cu–Mn ferrites having the general formula of Mg 0.9Cu 0.1Mn 0.1In x Fe 1.9− x O 4 with 0.0≤ x≤0.4 have been studied. X-ray diffraction (XRD) patterns of the samples indicated the formation of single-phase cubic spinel structure up to 0.2 and mixed phase (cubic and tetragonal phase) for samples x≥0.3. The relation of conductivity with temperature revealed a semiconductor to semimetal behavior as In +3 concentration increases. Variation in the universal exponent s with temperature indicates the presence of two hopping conduction mechanisms: the correlated barrier hopping (CHB) at low In +3 content x≤0.1 and small-polaron (SP) hopping at In +3 content x≥0.2. The variation in dielectric permittivity ( ε′, ε″) with temperature at different frequencies shows a normal behavior for the studied compounds, while the variation in dielectric loss tangent with frequency at different temperatures shows abnormal behavior with more than relaxation peak. The conduction mechanism used in the present study has been discussed in the light of electron exchange between Fe 3+ and Fe 2+ ions and hole hopping between Mn 2+ and Mn 3+ ions at the octahedral B-sites.

Structural and magnetic properties of LiMn 1.5Fe 0.5O 4 spinel oxide

Geometrical frustration, which arises from the topology of a well-ordered structure rather than from disorder, has recently become a renewed interest. In particular, geometrical frustration among spins in the spinel oxides can lead to exotic low-temperature states. We reported a joint experimental and theoretical investigation of Fe-doping effect on LiMn 2O 4 spinel oxide in which magnetic moments have geometrical frustration. The structural and physical properties of LiMn 1.5Fe 0.5O 4 were studied by means of Mossbauer spectroscopy, X-ray diffraction, scanning electron microscope (SEM), electrical and magnetic measurements. Electronic conductivity measurements showed that Verwey-type transition is absent in heavily Fe-doped LiMn 2O 4. In addition, LiMn 1.5Fe 0.5O 4 exhibits a semiconductor characteristic in resistivity with an energy gap E g =0.27 eV, which is consistent with our first-principle simulation. A large resistivity at room temperature for LiMn 1.5Fe 0.5O 4 indicates low concentration of conduction electrons corresponding to electronic localization behavior. X-ray diffraction refinement as well as Mossbauer analysis suggests that Fe ions preferentially substitute for Mn ions on the octahedral B-sites. Moreover, small amount of Fe replace for Li ions to form a site inversion in spinel structure. In contrast to the pure and low-Fe-doped LiMn 2O 4 samples, LiMn 1.5Fe 0.5O 4 has an antiferromagnetic transition at T N =34 K. The Fe dopants enhance the antiferromagnetic interaction among moments accompanied by breaking the original moment equilibrium and suppressing the magnetic frustration in LiMn 2O 4.