Mn Substitution Research Articles

Microstructure, magnetic properties, and loss performance of the Cu-substituted MnZn ferrites

While the Cu substitution in NiCuZn ferrites is known to enhance densification and increase the initial permeability (μi), little is known about its effects in the MnZn based ferrites, which naturally possess a higher saturation magnetization (Ms) and μi. In this study, the effects of Cu substitution for Mn on the power MnZn ferrites (Mn0.71-xCuxZn0.22Fe2.07O4, x = 0.00–0.35) are investigated. With increasing Cu content, enhanced density, reduced porosity, and significant grain growth are observed. The cation distribution was determined using the Rietveld refinement, showing the strong tendency of Cu2+ ions to occupy the octahedral sites of the spinel lattice. The magnetization curves show reduced Ms with increasing Cu content. The magnetic anisotropy (|K|) was also determined from the magnetization curves using the law of approach to saturation and is seen to be increased by the increasing Cu content. The reduced Ms and increased |K| lead to the dramatic reduction of μi from 2503 (x = 0.00) to 151 (x = 0.35) at room temperature. Despite the reduced Ms at room temperature, the Curie temperature (TC) is seen to increase with increasing Cu content from x = 0.05 to x = 0.35, indicating the relocation of cations at an elevated temperature. The cut-off frequency (fr) is increased with increasing Cu content, which corresponds to the reduced μi. Moreover, the core loss (Pcv) of the MnCuZn ferrites was tested at 100kHz/200 mT, 200kHz/125 mT, and 300kHz/100 mT at room temperature, and is found to deteriorate with the increasing Cu content.

Multi redox and oxygen vacancies govern the highly active manganese doped SrTiO3 cathode in rechargeable alkaline zinc battery

Rechargeable alkaline zinc batteries (RAZBs) have been facing big challenges of low energy density even they are inexpensive and safe. SrTiO3 has aroused strong interests as cathode of RAZBs based on their promising properties of strong redox properties and better thermal stability. However, the low electric conductivity and inadequate access sites of SrTiO3 limit their applications. Herein, Mn is successfully doped into SrTiO3 using facile one-pot hydrothermal method, which functions as an advanced cathode for RAZBs. In comparison with SrTiO3, partial substitution of Mn for Ti site in SrTiO3 lattice can endow SrTiO3 with enhanced electric conductivity, improved specific surface area as well as active sites of the SrTiO3. This is due to discovery of multi redox reaction of Mn and lattice vacancies. As a result, the Zn//Mn-STO battery demonstrate an excellent capacity of 744 mA h cm−3, good stability, and high energy density of 90 mWh cm−3. These outperforming of Mn-STO as cathode holding a great potential to prepare high-performance battery for future portable electronics.

Modulation of magnetic and dielectric properties by Al3+ substitution in Ca3CoMnO6 ceramics

We report a detailed study of the influence of non-magnetic Al3+ doping on the microstructure, magnetic, and dielectric characteristics Ca3CoMnO6. The introduction of Al3+ leads to the suppression of competing short-range magnetic orders, a gradual disappearance of the spin freezing peak in Ca3CoMn1-xAlxO6 was observed, accompanied by the release of magnetic frustration. Moreover, a weakening of the antiferromagnetic order in Ca3CoMnO6 was attributed to the dilution effect induced by non-magnetic Al3+ within the Co-Mn-Co-Mn spin chains. The dielectric measurements exhibit excellent agreement with the magnetic measurements. The substitution of Mn4+ with Al3+ results in the attenuation of relaxor ferroelectric behavior, accompanied by a decrease in the static freezing temperature Tf and an increase in the activation energy Ea. It indicates that Al3+ substitution could well suppress the formation of polar nanoregions. With introducing Al3+ the magnetodielectric effect of Ca3CoMnO6 is also significantly enhanced. For the x = 0.15 sample, the magnetodielectric effect undergoes a notable variation of approximately 10 % under a magnetic field of H = 4 T.

Ab-initio study of structural, electronic, phonon, X-ray spectroscopy, and the optoelectronic properties of D-block metals (Cr, Mn, Co, and Ni) substitution of barium oxide based-perovskites

Recently, transition metal doped superlattice has shown an anomalous optical band gap of 1.6 eV, about 1 eV lower than either parent element (Barium) majorly, making it appropriate for several applications including magnetism and superconducting materials. In the current study, the structural, electronic, phonon, thermodynamic, and the magnetic ordering of BaXO3 (X = Cr, Mn, Co, and Ni) has been examined using density functional theory (DFT). From the results, the investigated materials show a ferromagnetic behavior with the band gap of range 0.95–1.04 eV, and average absolute magnetization are 2.64, 3.67, 3.19, and 0.01 Bohr magneton/cell for BaCrO3, BaMnO3, BaCoO3, and BaNiO3, respectively. Furthermore, it is conceivable that the Compton profiles of BaXO3(X= Cr, Mn, Co, and Ni) are magnetic due to the substantial exchange-correlation dependence of their Compton profiles, which is shown from the phonon and X-ray distributions, thermodynamic calculation, and mechanically portrayed features of BaXO3. It was further discovered that doping could increase each TM (Cr, Mn, Co, and Ni) atom's magnetic moment. This study demonstrates a novel method for utilizing this revolutionary kind of cubic ferrites for spintronic applications in solid-state electronics.

Correlating structural and magnetic ground states of 3d-5d based double perovskites: Evidence of two magnetic phase transitions

We present a detailed study on both the structural and magnetic properties of the Sr2RuMn1-xIrxO6double perovskite oxides with four different concentrations (x = 0, 0.25, 0.5 and 0.75). The main objective of the work is to study the effect of Ir substitution for Mn on the high-temperature crystallographic and low-temperature magnetic phases of the compounds. Thephase purity was confirmed by the Rietveld analysis of the X-ray diffraction (XRD)pattern. The high temperature crystallographic information of the compounds was investigated by the help of high temperature X-ray diffraction and Raman spectroscopy. Signature of two structural phase transitions for x = 0.75 and one structural phase transition for x = 0 was seen. FESEM (Field emission scanning electron microscopy) with EDS (energy dispersive spectroscopy) of Ir-01 (x = 0.25) confirmed the presence of all the elements in the sample. The magnetic structure of all the samples have been studied at low temperature (5 K). The existence of two magnetic transitions for x = 0.5 and x = 0.75 are evident from the temperature dependent magnetization behavior.

Semi-empirical degradation rate estimation of TiFe1-xMnx alloy for thermochemical hydrogen compression durability tests

The substitution effects of Fe by Mn in TiFe1-xMnx (x = 0.1–0.5) alloys on the cyclic durability for thermochemical hydrogen compressors were investigated. In the substitution ratio range of 0.1–0.5, TiFe1-xMnx alloy shows a single CsCl phase structure, and thus is further used for a thermochemical hydrogen compressor at 500 °C. The compression tests are performed for 26 cycles in temperature range from 25 °C to 500 °C. The variation of hydrogen storage capacity during pressure composition isotherm test and structural identification by x-ray diffraction measurements are conducted to investigate the cyclic durability of TiFe1-xMnx alloy at the above compression conditions. The Mn substitution increased the cyclic durability of TiFe for the thermochemical hydrogen compressor, and 30% of Mn (TiFe0.7Mn0.3) is the optimum ratio for the reduction rate of hydrogen storage capacity and achieved maximum pressure. In addition, TiFe0.5Mn0.5, as the respective sample with the maximum capacity loss, was evaluated by the acceleration test to estimate the lifetime of the alloys. The reaction kinetics v0 [(H/M)/s] of the capacity loss of TiFe0.5Mn0.5 is defined as ln v0 = 1.68 ln (PH2/P0) − (2.39 × 1000)/T − 18.967. Therefore, it is possible to predict the durability of TiFe1-xMnx alloy at different pressure and temperature conditions by the presented acceleration test.

Negative thermal expansion in Co2-xMnxP2O7

Negative thermal expansion (NTE) is an abnormal phenomenon that only exists in few materials but is of importance in tailoring the coefficients of thermal expansion (CTE) in some advanced devices and instruments. Herein, we find that a large volume shrinkage occurs in Co2P2O7 crossing its structural transformation from α (P21/C) to β phase (C2/m) around 584 K which can be tuned even to below room temperature (RT) by the substitution of Mn2+ for Co2+. It is also found that the sintering temperature and the content of Mn2+ are crucial factors in controlling the proportions of α- and β-phases crystallized at RT and the rates of phase transition. A zero thermal expansion within a wide temperature window (173–573 K) is realized for Co1.4Mn0.6P2O7 sintered at 1173 K. The NTE arises from the lattice volume difference between the low temperature α-phase and high temperature β-phase while a higher content of Mn2+ and lower sintering temperature favorites for the coexistence of both phases at RT and lowering the phase transition rate. This work not only adds new members for the NTE family but also presents a method for regulating the onset, width, and rate of NTE by the interplay of substitution content and sintering temperature.

From Li to Na: Exploratory Analysis of Fe-Based Phosphates Polyanion-Type Cathode Materials by Mn Substitution.

Both LiFePO4 (LFP) and NaFePO4 (NFP) are phosphate polyanion-type cathode materials, which have received much attention due to their low cost and high theoretical capacity. Substitution of manganese (Mn) elements for LFP/NFP materials can improve the electrochemical properties, but the connection between local structural changes and electrochemical behaviors after Mn substitution is still not clear. This study not only achieves improvements in energy density of LFP and cyclic stability of NFP through Mn substitution, but also provides an in-depth analysis of the structural evolutions induced by the substitution. Among them, the substitution of Mn enables LiFe0.5 Mn0.5 PO4 to achieve a high energy density of 535.3 Wh kg-1 , while NaFe0.7 Mn0.3 PO4 exhibits outstanding cyclability with 89.6% capacity retention after 250 cycles. Specifically, Mn substitution broadens the ion-transport channels, improving the ion diffusion coefficient. Moreover, LiFe0.5 Mn0.5 PO4 maintains a more stable single-phase transition during the charge/discharge process. The transition of NaFe0.7 Mn0.3 PO4 to the amorphous phase is avoided, which can maintain structural stability and achieve better electrochemical performance. With systematic analysis, this research provides valuable guidance for the subsequent design of high-performance polyanion-type cathodes.

Negative magnetization, shielding current effect and divalent manganese in CaMn1-xTaxO3 manganites

Crystal and electronic structures, and magnetic properties of polycrystalline tantalum substituted manganites CaMn1-xTaxO3 (x = 0.00, 0.03, 0.06, 0.09 and 0.12) were studied by x-ray diffraction, x-ray absorption near edge spectroscopy (XANES) at Mn K-edge, and by magnetization measurements. Large changes of cell volume and magnetic transition temperature, in addition to shift of Mn K-edge spectra and change of shape of XANES spectra, indicate the existence of Mn3+ as well as Mn2+ species induced by the substitution of Mn4+ by Ta5+. Cell parameters and cell volume increase with increasing x because the Mn3+, Mn2+ and Ta5+ ions are larger that substituted Mn4+ ion. According to XANES results, at least the x = 0.00 sample is oxygen deficient. The negative magnetization was observed in the CaMnO3-δ sample, and a possible explanation of the phenomenon is given considering two canted (almost antiferro)magnetic sublattices and a shielding current, associated with the itinerant eg electrons, induced by the oxygen vacancies.

Impact of transition metal (Co and Mn) substitution on the structural and magnetic properties of BaFe12O19 nanoparticles towards permanent magnet application

Impact of transition metal (Co and Mn) substitution on the structural and magnetic properties of BaFe12O19 nanoparticles towards permanent magnet application

Effect of Mn substitution in Cr1-xMnxSbSe3 van der Waals ferromagnetic material

A solid-state reaction has been used to synthesize Cr1-xMnxSbSe3 samples with a concentration of 0 ≤ x ≤ 0.1. The crystalline structure of the prepared samples was determined by X-ray diffraction (XRD) patterns in a pure single phase. The magnetic properties of the ferromagnetic samples were determined using AC-Susceptibility instruments. Mn substitutions revealed non-monotonic changes in the transition temperature. The XRD patterns of all samples Cr1-xMnxSbSe3 indicate that the crystalline structure is orthorhombic. Moreover, the Mn substitutions did not appreciably change the lattice parameters in the prepared samples. The ac-susceptibility of all samples revealed a sharp first-order ferromagnetic transition at the Curie temperature Tc. The real part of AC susceptibility for all samples is normalized on temperature for various Mn concentrations. XRD and AC-susceptibility analyses agree with the other published work. The activation energy was obtained using the ac-susceptibility measurements at various frequencies.

The Effect of Substitution of Mn by Pd on the Structure and Thermomagnetic Properties of the Mn1-xPdxCoGe Alloys (Where x = 0.03, 0.05, 0.07 and 0.1).

In the present paper, the influence of partial substitution of Mn by Pd on structure, thermomagnetic properties, and phase transitions in the MnCoGe alloys was investigated. The studies of phase constitution revealed an occurrence of the orthorhombic TiNiSi-type and hexagonal Ni2Ti- type phases. Deep analysis of the XRD pattern supported by the Rietveld analysis allowed us to notice the changes in lattice parameters and quantity of recognized phases depending on the Pd content. An increase of palladium in alloy composition at the expense of manganese induced a rise in the Curie temperature. The values of ΔSM measured for the variation of external magnetic field ~5 T equaled 8.88, 23.99, 15.63, and 11.09 for Mn0.97Pd0.03CoGe, Mn0.95Pd0.05CoGe, Mn0.93Pd0.07CoGe, and Mn0.9Pd0.1CoGe alloy, respectively. The highest magnetic entropy change ΔSM was observed for samples with Pd content x = 0.05 induced by magnetostructural transformation. The analysis of the n vs. T curves allowed confirmation of the XRD and DSC results of an occurrence of the first-order magnetostructural transition in Mn0.95Pd0.05CoGe and Mn0.93Pd0.07CoGe alloys samples.

Ti, V, Cr, Mn, Co, and Ni substitution effect on structural, electronic, thermodynamic and magnetic properties of MgS and MgSe for spintronics

For the purposes of fitting the characteristics of the Magnesium sulfide (MgS) and, Magnesium selenide (MgSe) semiconductors in Spintronic applications, a theoretical ab-initio investigation of Transition metals (TM=Ti, V, Cr, Mn, Co, Ni) substitution is performed. The equilibrium properties have been studied in the zinc-blende phase of MgS and MgSe. The effects of temperature and pressure on the structural, electronic, thermodynamic, and magnetic properties of our systems are explored as well. It is found that the introduction of the TMs in MgS and MgSe brings out a half-metallic ferromagnetic behavior with 100% polarization around Fermi level in Ti, V, Cr, Co and Ni cases, contrary to the Mn case where the half-metallic feature does not appear. The double exchange mechanism was the mechanism responsible for magnetism in these systems. Finally, the high Curie Temperate (Tc) of the ferromagnetic systems reveals that Ti, Cr and V substitutions could play a significant role in spintronic applications.

Large perpendicular magnetic anisotropy, high curie temperature, and half-metallicity in monolayer CrSI induced by substitution doping

The experimental discovery of two-dimensional (2D) intrinsic ferromagnets have sparked intense interest due to their potential applications in spintronics. However, the small magnetic anisotropy and low Curie temperature (TC) hinder their applications. Herein, through comprehensive first-principles calculations and Monte Carlo simulations, we investigate how Mn substitution doping affects the structure, electronic structure, magnetic properties, and TC of monolayer CrSI. Our calculations show that in contrast to ferromagnetic semiconductor with a TC of 175 K of monolayer CrSI, Mn doped monolayer CrMnS2I2 is a half-metallic ferromagnet with a TC of 312 K. Different from in-plane magnetic anisotropy of monolayer CrSI, the easy axis of monolayer CrMnS2I2 is out-of-plane, and the magnetic anisotropy of monolayer CrMnS2I2 can reach to 1.434 meV/atom, which is much larger than 0.001 meV/atom of monolayer CrSI. Additionally, the phonon dispersion, ab initio molecular dynamics simulations, formation energy, and elastic constants calculations indicate that monolayer CrMnS2I2 possesses excellent stability. Our findings provide a promising route to realize 2D intrinsic ferromagnetic half-metallic materials with a high TC and a large perpendicular magnetic anisotropy.

Effect of Mn Substitution on the Dielectric Constant and Breakdown Voltage of Anti-ferroelectric PLZT

Effect of Mn Substitution on the Dielectric Constant and Breakdown Voltage of Anti-ferroelectric PLZT

Improved hydrogen storage properties of low-cost Ti–Cr–V alloys by minor alloying of Mn

V-based BCC solid-solution alloys have been considered as promising hydrogen storage materials due to their high hydrogen storage capacity; however, the low effective hydrogen desorption capacity and high cost of pure V have limited their practical application in fuel cell vehicles or devices. Herein, a low-V TiCr1.2(V–Fe0.203)0.6 hydrogen storage alloy with a hydrogen storage capacity of 3.35 wt% has been developed by using a low-cost FeV80 as raw material. To further increase the effective hydrogen desorption capacity, cheap Mn is first used to partially substitute for Cr in FeV80-based alloy. The Mn substitution alloy achieves an effective hydrogen desorption capacity of 2.07 wt% cutting-off at 0.1 MPa with good activation performance. It is ascribed that the minor alloying of Mn increases the dehydrogenation plateau pressure and reduces the hysteresis and the enthalpy change value. The dehydrogenation enthalpy decreases from 34.84 kJ/mol to 31.51 kJ/mol. The synergistic effect of Mn and Fe increases the abundance of the C14 Laves phase, which plays a catalytic role in hydrogen absorption and desorption. The cost of TiCr1.1Mn0.1(V–Fe0.203)0.6 alloy is much lower than that of using pure V, and even lower than some AB2 alloys based on cost estimation. The results of this study would provide a reference for the application of low-cost Ti–Cr-(FeV80) alloys for hydrogen storage.

Phase equilibria of the Co-Cr-Mn ternary system at 700 ℃

The isothermal phase diagram of the Co-Cr-Mn ternary system at 700 ℃ was experimentally determined via field-emission electron probe microanalysis/wavelength dispersive X-ray spectrometry and electron backscatter diffraction analyses. Three-phase regions of αCo(para)+ βMn+ σ and αMn+ βMn+ σ were confirmed via equilibrated microstructures; however, three-phase microstructures related to αCo(para)+ εCo+ σ and α’+ (Cr)+ σ were not observed in our study. The three-phase region of αCo(para)+ εCo+ σ was estimated to be very narrow because the phase boundaries between the αCo(para) and εCo phases were different within 2 at% for the Co, Cr, and Mn compositions. Furthermore, the α’ phase, presumed to be a nitride, was not observed in the microstructure equilibrated under a strictly controlled high-purity Ar gas (99.999%) atmosphere. The σ phase indicated a wide single-phase region similar to a previous study reported at temperatures between 900 ℃ and 1200 ℃. The αMn phase, which is stable below 727 ℃ in the Cr-Mn binary system and below 900 ℃ in the Co-Mn binary system, had a large Co solubility of 9.8 at% in the Co-Cr-Mn ternary system. The composition dependences on the lattice constants of the σ phase in the Co-Cr-Mn ternary system were examined via X-ray diffraction analysis; this analysis showed that the lattice constants a and c changed significantly with increasing Mn composition in the Co and Mn substitution, while the lattice constant of a was constant and c was slightly increased by increasing Mn composition in Cr and Mn substitution. From first-principles calculations, it was deduced that increases or decreases in bonding lengths between the nearest atoms occupying the five sublattice sites were associated with small changes in the lattice constant when Mn replaced Cr. The hardness of the σ phase decreased with increasing c/a, and the hardness in the crystal orientation of (100) was more dependent on the Mn composition than that in the crystal orientation of (001).

Magnetic properties and magnetocaloric effects in Eu(Ti,Nb,Mn)O3 perovskites

In perovskite EuTiO3, the magnetic characteristics and magnetocaloric effect (MCE) can be flexibly regulated by converting the magnetism from antiferromagnetic to ferromagnetic. In the present work, a series of Eu(Ti,Nb,Mn)O3 compounds, abbreviated as ETNMO for convenience of description, was fabricated and their crystallography, magnetism together with cryogenic magnetocaloric effects were systematically investigated. The crystallographic results demonstrate the cubic perovskite structure for all the compounds, with the space group of Pm3m. Two magnetic phase transitions are observed in these second-order phase transition (SOPT) materials. The joint substitution of elements Mn and Nb can considerably manipulate the magnetic phase transition process and magnetocaloric performance of the ETNMO compounds. As the Mn content increases, gradually widened –ΔSM-T curves are obtained, and two peaks with a broad shoulder are observed in the –ΔSM-T curves for Δμ0H≤0–1 T. Under a field change of 0–5 T, the values of maximum magnetic entropy change (−ΔSMmax) and refrigeration capacity (RC) are evaluated to be 34.7 J/(kg·K) and 364.9 J/kg for EuTi0.8625Nb0.0625Mn0.075O3, 27.8 J/(kg·K) and 367.6 J/kg for EuTi0.8375Nb0.0625Mn0.1O3, 23.2 J/(kg·K) and 369.2 J/kg for EuTi0.8125Nb0.0625Mn0.125O3, 17.1 J/(kg·K) and 357.6 J/kg for EuTi0.7875Nb0.0625Mn0.15O3, respectively. The considerable MCE parameters make the ETNMO compounds potential candidates for cryogenic magnetic refrigeration.

Understanding effect of Mg and Mn equivalents on columnar-to-equiaxed transition of high-strength Al alloy fabricated by laser powder bed fusion

In this work, a Mg-riched/Mn-riched high strength Al graded alloy was fabricated by high-throughput laser powder bed fusion process. The effect of variation from Mg to Mn on the microstructure and mechanical properties of high strength Al alloy was investigated. A control of columnar to equiaxed grain structure transition in high strength Al alloy was achieved by adjusting the ratio of Mn to Mg element. Based on the kinetics simulation, the increase of Mn solutes can shorten the incubation time of Al nucleation and generate sufficient undercooling, which favors the formation of the equiaxed grains. A significant increase in strength from 362.2 MPa to 495.4 MPa can be obtained by the substitution of Mn to Mg in printed Al alloy due to the microstructure refinement and the precipitation strengthening of Al6Mn. An ageing treatment can improve the overall strength because of secondary phase precipitation of Al3Sc and Al6Mn. A strength/ductile trade off mechanical properties of UTS 564.7 MPa and Elongation 8.5% can be found with the Al-3.8Mn-2.8 Mg-0.78Sc-0.57Zr component.

Effect of Extra Cation Substitution on Magnetic Anisotropy of La-Co Co-Substituted M-Type Sr Ferrite

La-Co co-substituted M-type ferrite magnets have large coercivities and are used as high-performance ferrite magnets in motors. Enhancing the uniaxial magnetic anisotropy of base materials by the substitution of Co <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> improves the coercivity. Since cobalt is a rare element, reducing its use is of great industrial importance. This study deals with the effect of a small amount of Al, Cr, and Mn substitution for Fe on the magnetic properties of La-Co co-substituted M-type ferrites without increasing the amount of Co. The additional substitution of Mn was observed to be advantageous in improving the magnetic anisotropy.