14721-18-7Relevant articles and documents
Effect of nitrogen substitution on the structural and magnetic ordering transitions of NiCr2O4
Liu, Xin,Yin, Nan,Thomas, Tiju,Yang, Minghui,Wang, Junhu,Shi, Quan
, p. 112140 - 112147 (2016)
The nitrogen (N) doped spinel NiCr2O4 has been synthesized at 773 K (N500) and 873 K (N600) by ammonolysis of NiCr2O4 powders to study the effect of anion doping on its structural and magnetic properties. The N contents are determined by thermogravimetric oxidation, yielding a composition that can be described as NiCr2O3.68N0.21 (N500) and NiCr2O3.55N0.30 (N600). X-ray photoelectron spectroscopic studies suggest that N3? species partly substitute the oxygen in the lattice and oxygen vacancies exist in the N doped samples. There is evidence that in the nitrided sample, the Cr ion is most likely in a mixed oxidation state. As the N content increases, the structure at room temperature changes from tetragonal to the cubic phase; N500 is only partially tetragonal; N600 is completely cubic. Such structural change is the consequence of the depression of the cooperative Jahn-Teller effect of Ni2+ in the tetrahedral A site caused by the presence of N3?. Combined heat capacity and temperature dependent magnetic susceptibility measurements give clear evidence of the magnetic and structural transitions in the N doped NiCr2O4. The Jahn-Teller transition temperatures decrease with increasing N content; this is likely due to increased covalency and hence enhanced contribution of the angular momentum and the spin-orbit coupling to local chemical bonding around Ni2+. Antiferromagnetic transitions are observed at TS = 23 K and 22 K for N500 and N600, respectively. Hence there is indeed a lowering of transition when compared to pure NiCr2O4 (28 K). The magnetic loops at different temperatures confirm that the material behaves as a paramagnet over a wide range of temperatures T ～ 80-350 K. The material also exhibits a canted ferrimagnetic structural transition between 30 and 70 K. We also report evidence for increased frustration and lowered correlation length in N doped compounds compared to the parent NiCr2O4. The present study on N? doping effects on the structure and magnetic properties of this NiCr2O4 is expected to be useful for tailoring the ferric phase transitions through anion substitutions.
Duval, C.
, (1962)
Dielectric relaxation and small polaron hopping transport in sol-gel-derived NiCr2O4 spinel chromite
Javed, Muhammad,Khan, Ayaz Arif,Kazmi, Jamal,Mohamed, Mohd Ambri,Khan, Muhammad Nasir,Hussain, Mubushar,Bilkees, Rehana
, (2021)
Herein, we have synthesized NiCr2O4 chromite by the sol-gel auto-combustion route. The refined X-ray powder diffraction pattern confirmed the single-phase formation of the material, which crystallized in a cubic normal spinel structure with space group Fd3m. The complex impedance study indicated the existence of relaxation phenomenon and predicted the semiconducting nature of the material. The frequency-dependent Nyquist plot modeled by (RGBCGB) (RGQG) equivalent circuit exhibited the effects of grain and grain boundary to the electrical response of the compound over the measured temperature range of 263-393 K. The experimental AC conductivity data followed Jonscher's double power-law behavior, and the frequency exponent profile suggested small polaron hopping as the most probable transport mechanism for the sample. The complex modulus analysis showed the non-Debye type behavior of the material. In contrast, the dielectric constant exhibited dispersion in the low-frequency regime with a large tangent loss directly related to temperature.
Atanasov, M.,Kesper, U.,Ramakrishna, B. L.,Reinen, D.
, p. 1 - 18 (1993)
Spin glass and exchange bias behavior in magnetically frustrated Ni1?xMgxCr2O4 (x = 0.0–0.50)
Borah, Ritupan,Ravi
, (2020)
Single-phase polycrystalline samples of Ni1?xMgxCr2O4 (x = 0.0–0.50) were prepared by sol gel route and their structural and magnetic properties were studied. Structural transformation from tetragonal (I41/amd) to cubic (Fd3-m) phase is observed at room temperature due to Mg substitution. Mg substitution gives rise to reduction in ferrimagnetic and antiferromagnetic transition temperatures along with a signature of spin glass like phase in samples of intermediate compositions, i.e., for x = 0.10, 0.20 and 0.30. The observed stretched exponential type relaxation of thermoremanent magnetization and the highly frustrated magnetic behavior confirm the glassy magnetic phase. Significant increase in exchange bias field under field cooled condition for the Mg substituted samples is observed. The origin of exchange bias in theses samples is explained by considering exchange anisotropy between the ferrimagnetic and antiferromagnetic components of canted spin. The training effect of exchange bias field is also observed.
Catalytic Decomposition of Isopropanol over Chromite Spinels MCr2O4 (M=Ni, Mn and Mg)
Balasubramanian, Krithivasa,Krishnasamy, Vengaimuthu
, p. 2665 - 2672 (1986)
The decomposition of isopropanol over nickel, manganese and magnesium chromite spinel catalysts has been investigated in the vapour phase in an integral reactor.Its decomposition follows first-order kinetics.Kinetic and thermodynamic parameters have been calculated using the Arrhenius and Eyring equations.The activity pattern is found to be NiCr2O4>MnCr2O4>MgCr2O4.The chromite spinels have been characterised by X-ray studies, i.r. spectral analysis, conductivity and thermoelectric potential measurements.All three chromites were found to be p-type semiconductors in the temperature range 150-400 deg C.Exclusive dehydrogenetion is shown by NiCr2O4 and MnCr2O4, whereas MgCr2O4 functions as a dehydrogenation and dehydration catalyst.A linear correlation exists between the entropy of activation and the activation energy for electrical conduction for the chromite spinels studied.
[NiEn3]CrO4: Structure, thermal properties, and pseudomorphism
Khranenko,Komarov, V. Yu.,Gerasimov, E. Yu.,Zadesenets,Maksimovsky,Gromilov
, p. 1448 - 1452 (2017)
The crystal structure of [NiEn3]CrO4 (En is ethylendiamine), C6H24CrN6NiO4 is studied: a = 9.0408(5) ?, c = 9.7466(4) ?, V = 689.92(8) ?3, space group P63/mmc, Z = 2, dx = 1.704 g/cm3, Ni–N 2.133(9) ?, ∠N–Ni–N 82.4(5)°. The thermal properties are determined. When it is heated in a hydrogen atmosphere, a mixture of nanocrystalline Ni and Cr2O3 powders with coherent scattering regions of 59 nm and 90 nm respectively is formed. It is demonstrated that thermal decomposition products consist of pseudomorphic particles that inherit the sizes and shapes of initial [NiEn3]CrO4 single crystals.
Enhanced magnetodielectric response in Dy modified NiCr2O4
Mandal,Singh, Ripandeep,Das,Sarkar, Tarapada,Nath
, p. 49 - 55 (2017)
The chemically synthesized high purity spinel NiCr2?xDyxO4 (x?=?0, 0.1) samples have been characterized using magnetic and dielectric measurements in presence of high magnetic field. Crystal and magnetic structure of the samples have been determined by analyzing neutron diffraction data recorded between temperature of 6?K and 300?K. NiCr2O4 crystallizes in tetragonal phase with the space group of I41/amd whereas NiCr1.9Dy0.1O4 crystallizes in the mixed phase of cubic (space group of Fd3ˉm) and tetragonal phases at room temperature. An additional phase of DyCrO3 with orthorhombic structure has been found in the Dy doped compound. The lattice parameter a increases and the c decreases in tetragonal structure with the substitution of Dy in Cr site. Both the samples show superlattice reflection peak indicating the presence of long range AFM ordering (transverse component) below 40?K. But the saturation magnetization slightly increases after Dy doping. An anomaly observed near Curie temperature in ε′ (T) of NiCr2O4 and NiCr1.9Dy0.1O4 demonstrates the contribution of coupling between ferroelectricity and ferrimagnetism in the compounds. A linear correlation between the difference in dielectric constant and the field dependent squared magnetization for both the samples has been observed. The spin–spin interactions are most likely responsible for the observed magnetodielectric (MD) effect due to the magnetodielectric hysteresis in both parent and doped samples. Interestingly the MD% is found to increase with Dy doping.
Structural and magnetic properties of Cu-Ni-Cr spinel oxides
Tovar,Torabi,Welker,Fleischer
, p. 196 - 198 (2006)
The compounds CuCr2O4 and NiCr2O4 crystallize at room temperature in a tetragonal distorted spinel structure, s.g. I41/amd, with axes ratio c/a1, respectively. The distortion is caused by the Jahn-Teller ions Cu2+ and Ni2+ which flatten or elongate their surrounding oxygen tetrahedron. CuCr2O4 and NiCr2O4 form a complete solid solution series Cu1-xNixCr2O4 where for 0.825a temperature-dependent crystallographic phase transition from cubic to tetragonal symmetry between 865 K (CuCr2O4) and 310 K (NiCr2O4). The phase Cu0.15Ni0.85Cr2O4 undergoes a second crystallographic transition to orthorhombic symmetry, space group Fddd, at T=300 K. The neutron diffraction experiments as well as SQUID measurements reveal magnetic ordering of the ions between 150 and 50 K which partially occurs as a two-step mechanism.
Exchange bias and magnetization reversal in Ni(Cr1?xFex)2O4 (x=0–0.20)
Barman, Junmoni,Babu,Ravi
, p. 300 - 305 (2016)
Exchange bias and magnetization reversal in single phase samples of Ni(Cr1?xFex)2O4 (x=0–0.20) were studied through magnetic measurements. Substitution of Fe for Cr changes the crystal structure at room temperature from tetragonal (space group: I41/amd) to cubic (space group: Fd3ˉm) form. Temperature variation of magnetization measurements show that these samples undergo ferrimagnetic transitions and the transition temperature (TC) increases from 73 K for x=0.0 to 314 K for x=0.20. An interesting magnetization reversal phenomenon was observed for x=0.06 sample with a magnetic compensation temperature of 49 K. M–H loop measurements at different temperature show the signature of presence of strong antiferromagnetic interactions especially at low temperature (Ta maximum exchange bias field of 5670 Oe is observed for x=0.06 sample and it is explained by considering the exchange anisotropy between the ferrimagnetic and the antiferromagnetic components. The exchange bias field and the vertical shift in magnetization decrease exponentially with increase in temperature.
A magnetocaloric study on the series of 3d-metal chromites ACr2O4 where A = Mn, Fe, Co, Ni, Cu and Zn
Ali, Anzar,Singh, Yogesh
, (2019/12/26)
The 3d-metal chromites ACr2O4 where A is a magnetic ion, show the paramagnetic to ferrimagnetic phase transition at TC while for non-magnetic A-site ion, ACr2O4 show paramagnetic to antiferromagnetic phase transition at TN. In this report, we present the detailed study of magnetic and the magnetocaloric effect (MCE) of the 3d-metal chromites ACr2O4 (where A = Mn, Fe, Co, Ni, Cu, and Zn) near TC and TN. We find the magnitude of MCE (-ΔSM) decreases on decreasing the magnetic moment of A-site ion with an exception for CuCr2O4. Additionally, to know more about the order and nature of phase transition, we have made a scaling analysis of (-ΔSM) for all the chromites across the phase transition temperatures TC and TN.
