Structural phase transition and spontaneous exchange bias in NiCr1.9Fe0.1O4 nanoparticles: XRD, EXAFS and magnetic measurements

Pandey, Gaurav; Aquilanti, Giuliana; Sastry, P. U.; Rath, Chandana

doi:10.1016/j.ceramint.2019.04.085

Cited by 7 publications

(5 citation statements)

References 41 publications

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“…Figure 7 shows the magnetic contributions measured in the temperature range of 3.5–250 K. It is clear from Figure 7a that a weak and broad (111) fundamental reflection arises near T C and its intensity increases with a decrease in temperature down to 3.5, indicating the presence of a long‐range ferrimagnetic structure. [ 11,20,21 ] In our previous reports on NiCr 2 O 4 nanoparticles, transition to spin spiral magnetic ordering has been observed, showing satellite peaks at 1.08 and 1.69 Å −1 below 30 K. [ 12 ] However, in the present case, no such satellite peaks are observed in the temperature range of 3.5–250 K, indicating the absence of spin‐spiral ordering.…”

Section: Resultscontrasting

confidence: 37%

“…It can be noted that the estimated T C for NiCr 1.7 Fe 0.3 O 4 nanoparticles is almost 29 K higher compared with T C ≈230 K reported for its bulk counterpart by Park et al [ 18 ] This enhancement in T C corroborates well with the enhanced T C observed for x = 0, 0.1 and 0.2 nanoparticles compared to their bulk counterparts. [ 11,12 ] Moreover, a significant increase in T C compared with the T C in NiCr 2 O 4 nanoparticles is attributed to the increase in exchange interaction between the magnetic cations occupying the A and B sites. Below T C , the irreversibility between the M FC and M ZFC is observed at irreversible temperature, T irr ≈ 244 K. The large bifurcation between the M FC and M ZFC below T irr suggests the presence of uncompensated spins accompanied by strong magnetic anisotropy.…”

Section: Resultsmentioning

confidence: 99%

“…[ 7,8 ] Interestingly, these phase transitions in NiCr 2 O 4 could be easily tuned by the partial substitution of transition elements for the Ni/Cr‐site, which could further offer new enhanced properties such as exchange bias, magnetocaloric effect, magnetic switching effect, magnetization reversal, large coercivity, and so on. [ 9–12 ] The exchange bias phenomenon which is manifested by the asymmetrical magnetic hysteresis loop about the field and/or magnetization axis has important application in the spin valves, read heads for recording devices, and magnetic tunnel junction‐based devices. [ 13,14 ] Exchange bias is generally induced by the unidirectional exchange anisotropy at the interface between irreversible and reversible magnetic phases.…”

Section: Introductionmentioning

confidence: 99%

“…[ 15 ] In our recent report, we have shown unusually high exchange bias field of ≈875 and ≈2069 kA m −1 after substituting the Cr‐site with 10 and 20 at% of Fe in NiCr 2 O 4 lattice, respectively. [ 11,12 ]…”

Section: Introductionmentioning

confidence: 99%

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Structural Transformations and Magnetic Properties of Mixed Spinel‐Type NiCr_1.7Fe_0.3O₄ Nanoparticles

Pandey

Rath

2021

Physica Status Solidi (b)

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Structural and magnetic properties of NiCr1.7Fe0.3O4 nanoparticles, synthesized by a facile coprecipitation method, are examined using temperature‐dependent X‐ray diffraction, neutron scattering with XYZ polarizations, and magnetic measurements. The structural analysis demonstrates the stabilization of the cubic phase down to 200 K, followed by a low‐temperature tetragonal phase at 100 K and an orthorhombic phase below 50 K. The refined occupancies of cations demonstrate that the NiCr1.7Fe0.3O4 is a mixed spinel compound, wherein B sites are populated by ≈85% Cr3+ and ≈15% Ni2+ cations and A sites are populated by ≈70% Ni2+ and ≈30% Fe3+ cations. As a consequence, the reduction in the occupancy of Jahn–Teller active Ni2+ (triply degenerate: e4 t4) at A site is attributed to the stabilization of the cubic phase below room temperature. Temperature‐dependent magnetization and neutron scattering with XYZ polarizations measurements reveal the ferrimagnetic nature of the magnetic phase and the absence of spin‐spiral ordering in NiCr1.7Fe0.3O4 nanoparticles. Furthermore, field‐dependent magnetization measurement demonstrates an exchange bias field of ≈134.5 kA m−1 at 5 K. The training effect measurement is performed to discuss the origin of exchange bias based on different phenomenological models such as power‐law and multiexponent models.

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Section: Resultscontrasting

confidence: 37%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Structural Transformations and Magnetic Properties of Mixed Spinel‐Type NiCr_1.7Fe_0.3O₄ Nanoparticles

Pandey

Rath

2021

Physica Status Solidi (b)

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“…Generally, with increase in external magnetic field, the difference in ZFC and FC magnetization decreases indicating low anisotropy. However, enhancement in splitting thus indicates an increase in anisotropy with field [49].…”

Section: Structure and Microstructurementioning

confidence: 99%

Coexistence of tetragonal and cubic phase induced complex magnetic behaviour in CoMn₂O₄ nanoparticles

et al. 2023

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CoMn2O4 nanoparticles synthesized through facile co-precipitation technique, exhibit a mixed phase of tetragonal and cubic at room temperature. Rietveld fitting of the XRD pattern specifies 91.84% of the tetragonal phase and 8.16% of the cubic phase. Raman spectra and selected area electron diffraction pattern further confirm the structure. Transmission electron micrograph confirms the semi-spherical shape of the particles with average diameter 95 nm, are polycrystalline in nature. While 97% of Mn3+ and 3% of Co3+ occupy the octahedral site in the tetragonal phase, 52% of Mn3+ and 48% of Co2+ occupy the octahedral site in the cubic phase. XPS analysis further confirms the presence of both +2 and +3 oxidation states of Co and Mn. Magnetic measurement shows two magnetic transitions, Tc1 at 165 K and Tc2 at 93 K corresponding to paramagnetic to a lower magnetically ordered ferrimagnetic state followed by a higher magnetically ordered ferrimagnetic state, respectively. While Tc1 could be due to the cubic phase having inverse spinel structure, Tc2 is attributed to the tetragonal phase with normal spinel. The non-collinear triangular spin canting configuration of Mn3+ cations in octahedral sites while results in large magnetization near Tc2, the decrement in magnetization at the vicinity of Tc1 indicates the decrement in Mn3+ in octahedral site, well corroborated with XRD. In contrast to general temperature dependent HC observed in ferrimagnetic material, an unusual temperature dependent HC with high spontaneous exchange bias of 2.971 kOe and conventional exchange bias of 3.316 kOe at 50 K are observed. Interestingly, a high vertical magnetization shift (VMS) of 2.5 emu/g is observed at 5 K, attributed to the Yafet-Kittel spin structure of Mn3+ in the octahedral site. Such VMS has the potential to revolutionize the future of ultrahigh density magnetic recording technology. 

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Competition between Cubic and Tetragonal Phase Induced Unusual Vertical Magnetization Shift and Exchange Bias in Co_xMn_3−xO₄ (1 ≤ x ≤ 2) Spinel Nanoparticles

Rajput,

Rath

2024

Physica Status Solidi (b)

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CoxMn3−xO4 (1 ≤ x ≤ 2) spinel nanoparticles synthesized through conventional coprecipitation technique exhibit the coexistence of tetragonal and cubic phases in the range of 1 ≤ x ≤ 1.5, while a pure cubic phase is observed for 1.75 ≤ x ≤ 2 at room temperature. Reduction in tetragonal phase fraction from 92 % for x = 1 to 47% for x = 1.5 is attributed to diminution of Jahn–Teller (J–T) active Mn3+ ions occupying the octahedral site of spinel lattice. X‐ray photoelectron spectroscopy confirms both +2 and +3 oxidation states for Co and Mn. Surprisingly, cubic and tetragonal phases exhibit magnetic transition, Tc1 and Tc2, corresponding to a paramagnetic to a high and low temperature ferrimagnetic state, respectively. Tetragonal phase induces high spontaneous (HSEB) and conventional (HCEB) exchange bias with unusually high vertical magnetization shift (VMS) than that of the pure cubic phase, shows maximum HCEB of 4.062 kOe for x = 1.5 and a VMS of 2.5 emu g−1 for x = 1. Such dependence of VMS and exchange bias on tetragonal to cubic phase ratio in CoxMn3−xO4 is demonstrated for the first time and interpreted based on the interaction between different arrangement of spins in tetrahedral and octahedral sublattice.

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Structural phase transition and spontaneous exchange bias in NiCr1.9Fe0.1O4 nanoparticles: XRD, EXAFS and magnetic measurements

Cited by 7 publications

References 41 publications

Structural Transformations and Magnetic Properties of Mixed Spinel‐Type NiCr_1.7Fe_0.3O₄ Nanoparticles

Structural Transformations and Magnetic Properties of Mixed Spinel‐Type NiCr_1.7Fe_0.3O₄ Nanoparticles

Coexistence of tetragonal and cubic phase induced complex magnetic behaviour in CoMn₂O₄ nanoparticles

Competition between Cubic and Tetragonal Phase Induced Unusual Vertical Magnetization Shift and Exchange Bias in Co_xMn_3−xO₄ (1 ≤ x ≤ 2) Spinel Nanoparticles

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Structural phase transition and spontaneous exchange bias in NiCr1.9Fe0.1O4 nanoparticles: XRD, EXAFS and magnetic measurements

Cited by 7 publications

References 41 publications

Structural Transformations and Magnetic Properties of Mixed Spinel‐Type NiCr1.7Fe0.3O4 Nanoparticles

Structural Transformations and Magnetic Properties of Mixed Spinel‐Type NiCr1.7Fe0.3O4 Nanoparticles

Coexistence of tetragonal and cubic phase induced complex magnetic behaviour in CoMn2O4 nanoparticles

Competition between Cubic and Tetragonal Phase Induced Unusual Vertical Magnetization Shift and Exchange Bias in CoxMn3−xO4 (1 ≤ x ≤ 2) Spinel Nanoparticles

Contact Info

Product

Resources

About

Structural Transformations and Magnetic Properties of Mixed Spinel‐Type NiCr_1.7Fe_0.3O₄ Nanoparticles

Structural Transformations and Magnetic Properties of Mixed Spinel‐Type NiCr_1.7Fe_0.3O₄ Nanoparticles

Coexistence of tetragonal and cubic phase induced complex magnetic behaviour in CoMn₂O₄ nanoparticles

Competition between Cubic and Tetragonal Phase Induced Unusual Vertical Magnetization Shift and Exchange Bias in Co_xMn_3−xO₄ (1 ≤ x ≤ 2) Spinel Nanoparticles