Pith. sign in

REVIEW 2 major objections 6 minor 45 references

Antiphase boundaries in single-phase nanocrystalline NiCo2O4 produce both large exchange bias and large negative magnetoresistance.

Reviewed by Pith at T0; open to challenge. T0 means a machine referee read the full paper against a public rubric. the ladder, T0–T4 →

Challenge this review Re-run · record.json Download PDF Read on arXiv ↗

T0 review · grok-4.5

2026-07-15 03:42 UTC pith:S7XZBGJX

load-bearing objection Solid experimental report of large EB and multi-order MR in as-synthesized NCO, both tied to APBs; the causal link is correlative rather than quantified, but the data package is consistent and referee-worthy. the 2 major comments →

arxiv 2607.12740 v1 pith:S7XZBGJX submitted 2026-07-14 cond-mat.mtrl-sci

Antiphase boundary-driven large exchange bias and negative magnetoresistance in NiCo2O4

Biswanath Pramanik , Pushpesh Pathak , Binoy K. Hazra This is my paper
classification cond-mat.mtrl-sci
keywords Spinel oxidesExchange biasNegative magnetoresistanceAntiphase boundaryNiCo2O4Nanocrystalline ferrimagnet
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper shows that as-synthesized single-phase NiCo2O4 nanoparticles carry a sizable exchange-bias effect and a large negative magnetoresistance that both come from the same structural defect: antiphase boundaries between ferrimagnetic grains. When the material is field-cooled, the magnetic hysteresis loop shifts both horizontally and vertically, giving an exchange-bias field of about 375 Oe at 5 K that vanishes near 300 K. The same sample exhibits roughly 31.5 percent negative magnetoresistance at 10 K whose low-field butterfly shape tracks the coercive field and whose field dependence requires higher-order powers of the reduced magnetization. High-resolution transmission electron microscopy images of the lattice directly reveal the antiphase boundaries. Because the defects sit inside a single material rather than at an engineered multilayer interface, the work points toward simpler oxide platforms for spintronic devices that need an intrinsic bias field.

Core claim

In single-phase nanocrystalline NiCo2O4, antiphase boundaries create antiferromagnetic or frustrated exchange coupling between neighbouring ferrimagnetic domains; that coupling produces both the observed exchange bias (horizontal and vertical loop shifts) and the large negative magnetoresistance that scales as a sum of even powers of reduced magnetization.

What carries the argument

Antiphase boundaries (APBs): planar defects in which the spinel lattice is shifted by a fraction of a unit cell, generating antiferromagnetic or frustrated exchange across the interface between two ferrimagnetic grains.

Load-bearing premise

The imaged antiphase boundaries, rather than surface spin disorder, residual secondary phases or inter-particle dipolar coupling, are the dominant source of the unidirectional anisotropy that produces the measured exchange-bias magnitude.

What would settle it

A controlled series of NiCo2O4 samples whose HRTEM-quantified APB density is varied while particle size and cation stoichiometry are held fixed should show exchange-bias field and high-order magnetoresistance coefficients that scale linearly with that density; absence of such scaling would falsify the claim.

Watch this falsifier — get emailed when new claim-graph text bears on it.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit.

Referee Report

2 major / 6 minor

Summary. The manuscript reports large exchange bias (HEB ≈ 375 Oe at 5 K, vanishing near 300 K) with both horizontal and vertical hysteresis shifts, and large negative magnetoresistance (~31.5% at 10 K, butterfly-shaped at low field) in as-synthesized single-phase nanocrystalline NiCo2O4 prepared by sol-gel combustion. Structural characterization (Rietveld XRD, SAED, XPS cation ratios, EDS) supports a mixed-valence inverse spinel without secondary phases. Magnetic data show ZFC/FC irreversibility, finite room-temperature coercivity, and non-saturating M-H loops; transport data show semiconducting ρxx(T) fitted to successive IGT/VRH/NNH regimes and MR that scales as Σ Ai (M/Ms)2i. The authors attribute both EB and MR to antiphase boundaries that produce antiferromagnetic or frustrated exchange between ferrimagnetic domains, and present HRTEM/IFFT images of the [400] plane as direct evidence of APBs.

Significance. If the APB origin is correct, the work shows that a single-phase nanocrystalline spinel can host sizable unidirectional anisotropy and large low-field MR without intentional FM/AFM bilayers or rock-salt interfacial phases. That would simplify materials design for field-free SOT/STT devices and add a bulk-nanoparticle route complementary to the thin-film NCO literature. The multi-term MR expansion and the matching of MR peaks to Hc are useful phenomenological diagnostics that other groups can apply. The result is of clear interest to the oxide-spintronics and nanocrystalline-magnetism communities, even if the causal link remains partly correlative.

major comments (2)
  1. §3.2–3.3 and Conclusion: The central claim that APBs are the dominant source of the observed HEB (~375 Oe) and vertical shift rests on correlation (HRTEM/IFFT of [400] plane in Fig. 5e,f; MR ~ Σ Ai (M/Ms)2i). No estimate of APB density or of the interfacial exchange energy is given, nor is there a control that varies APB density at fixed particle size. Alternative pinning sources common in nanocrystalline spinels—surface spin disorder, residual rock-salt NixCo1-xO (explicitly invoked for EB in NCO films in the cited literature [17]), or inter-particle dipolar coupling—are not quantitatively ruled out. XRD/SAED/XPS establish average single-phase character but cannot exclude minority interfacial or surface layers. A density-to-HEB estimate, a size-series control, or an annealing series that systematically changes APB density would convert the attribution from correlative to causal.
  2. §3.3 and Fig. 4d: The multi-term fit MR = Σ Ai (M/Ms)2i (i = 1,2,3) is presented as diagnostic of APBs, yet the Ai coefficients are free phenomenological parameters. The text does not state whether the same M(H) loops used for the fit were measured under identical field-cooling conditions as the MR, nor how Ms was defined for non-saturating loops. Without these details (or a comparison to a pure (M/Ms)2 model with quantified residuals), the higher-order terms remain suggestive rather than decisive evidence for APB-mediated spin disorder.
minor comments (6)
  1. Abstract and §3.2: HEB is quoted as ~375 Oe at 5 K in the abstract but the vertical-shift value is given at 10 K (0.8 emu/g). Align the temperatures or state both quantities at the same temperature.
  2. Fig. 3(d) and text: Blocking temperature is identified with the vanishing of HEB near 300 K; a short clarification that this is the EB blocking temperature (not the Néel temperature ~400 K) would avoid confusion.
  3. §3.1: Crystallite size from Scherrer (13 ± 1 nm) versus TEM particle size (23 ± 1 nm) is noted but not discussed; a brief remark on possible multi-domain or agglomerated particles would help.
  4. Fig. 5(e,f): The IFFT region is small; indicating the dislocation/APB with arrows and stating the imaging zone axis would strengthen the visual claim.
  5. References: A few recent works on APB-driven EB/MR in other spinels (e.g., Fe3O4) are cited; adding a short comparison of HEB magnitudes would place the 375 Oe result in context.
  6. Typographical: “Magnetic hysteresis (M-H) loop measurements has been recorded” (§3.2); “an tiferromagnetic” (Introduction); inconsistent use of NCO vs NiCo2O4.

Circularity Check

0 steps flagged

No circularity: EB and MR observations, phenomenological MR scaling, and independent HRTEM imaging of APBs are mutually consistent experimental evidence, not definitional or fitted reductions.

full rationale

The paper's central attribution (APBs produce both the observed HEB ~375 Oe with vertical shift and the butterfly MR ~-31.5% that scales as Σ Ai(M/Ms)2i) rests on three independent experimental channels: (i) field-cooled M-H loop shifts (Fig. 3c,d), (ii) MR(H) curves whose low-field peaks coincide with Hc and that require higher-order (M/Ms)2i terms for a phenomenological fit (Figs. 4d, 5a-c), and (iii) direct HRTEM/IFFT visualization of lattice discontinuities on the [400] plane (Fig. 5e,f). The Ai coefficients are free fit parameters that merely quantify the MR shape; they are never re-used to define or predict the existence of APBs or the value of HEB. Literature citations for the APB-MR and APB-EB mechanisms ([44-46] and related spinel work) are external and not load-bearing self-citations that close a definitional loop. No uniqueness theorem, ansatz smuggled via self-citation, or fitted quantity re-labeled as a first-principles prediction appears. The argument is correlative experimental inference of the usual materials-science type and is self-contained against the reported data.

Axiom & Free-Parameter Ledger

2 free parameters · 3 axioms · 0 invented entities

The paper is experimental; its load-bearing content is measured data plus standard domain knowledge of spinel magnetism and APB physics drawn from Fe3O4 literature. Free parameters appear only in the phenomenological MR fit. No new particles or forces are postulated.

free parameters (2)
  • Ai (i=1,2,3) coefficients of MR = Σ Ai (M/Ms)^{2i} = temperature-dependent; values shown only graphically in inset of Fig. 4(d)
    Phenomenological amplitudes fitted to the measured MR(H) curves at each temperature; their temperature dependence is reported but not predicted a priori.
  • activation/hopping parameters (Ea, T0, T0') in ρxx(T) fits
    Extracted by linear fits of ln ρ vs T^{-1}, T^{-1/4}, T^{-1/2} in three temperature windows; used only to identify transport regimes, not to claim the APB origin of EB/MR.
axioms (3)
  • domain assumption Antiphase boundaries in spinel oxides produce antiferromagnetic or frustrated exchange across the boundary, leading to non-saturating magnetization and butterfly magnetoresistance that scales with higher powers of (M/Ms).
    Imported from Fe3O4 literature (refs. 43–45) and applied without re-derivation to NCO in §3.3.
  • domain assumption Horizontal and vertical shifts of the hysteresis loop under field-cooling indicate unidirectional anisotropy and uncompensated pinned spins at an FM/AFM-like interface.
    Standard exchange-bias phenomenology (refs. 12, 35) used to interpret the ±5 T FC loops in §3.2.
  • domain assumption Rietveld refinement with χ^{2} = 1.48 and absence of extra SAED rings establish that the sample is single-phase cubic spinel without secondary rock-salt phases.
    Used in §3.1 to rule out the interfacial rock-salt mechanism reported for epitaxial NCO films.

pith-pipeline@v1.1.0-grok45 · 17419 in / 2988 out tokens · 30259 ms · 2026-07-15T03:42:12.641109+00:00 · methodology

0 comments
read the original abstract

Nickel-based spinel oxide has recently attracted significant attention due to its remarkable magneto-transport properties, promising various spintronic applications. In this study, we observe an exchange bias effect, where the magnetic hysteresis loop shifts both horizontally and vertically when single-phase nanocrystalline NiCo2O4 is cooled in the presence of an external magnetic field. The magnitude of the exchange bias field is approximately 375 Oe at 5 K, and this effect disappears around 300 K. Furthermore, NiCo2O4 shows semiconducting behaviour in longitudinal resistivity and demonstrates a substantial negative magnetoresistance of ~31.5% at 10 K. The magnetoresistance exhibits a butterfly-shaped behaviour at low magnetic fields and becomes almost linear at high magnetic fields. A detailed analysis of the negative magnetoresistance and exchange bias reveals that both phenomena originate from the formation of antiphase boundaries in the as-synthesized NiCo2O4 sample, as confirmed by the high-resolution transmission electron micrograph.

discussion (0)

Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.

Reference graph

Works this paper leans on

45 extracted references · 39 canonical work pages

  1. [1]

    A.P. N . Tchiomo, A. Sharma, S. Sajeev, A. Scheid, P.A. V. Aken, T. Harada, P. Ngabonziza, Magnetotransport properties in epitaxial films of metallic delafossite PdCoO2 : Effects of thickness and width variations in Hall bar devices, Phys. Rev. Mater 15 9 (2025) 055001, https://doi.org/10.1103/PhysRevMaterials.9.055001

    work page doi:10.1103/physrevmaterials.9.055001 2025

  2. [2]

    Sasmal and A

    A. Sasmal and A. K. Nayak, Morphology-dependent solvothermal synthesis of spinel NiCo2O4 nanostructures for enhanced energy storage device application , J. Energy Storage 58 (2023) 106342, https://doi.org/10.1016/j.est.2022.106342

    work page doi:10.1016/j.est.2022.106342 2023

  3. [3]

    Chen and D

    H. Chen and D. Yi, Spin–charge conversion in transition metal oxides, APL Mater. 9 (2021) 060908, https://doi.org/10.1063/5.0052304

    work page doi:10.1063/5.0052304 2021

  4. [4]

    Y. Zhu, X. Ji, Z. Wu, W. Song, H. Hou, Z. Wu, X. He, Q. Chen, and C. E. Banks, Spinel NiCo2O4 for use as a high-performance supercapacitor electrode material: Understanding of its electrochemical properties , J. Power Sources 267 (2014) 888-900, http://dx.doi.org/10.1016/j.jpowsour.2014.05.134

    work page doi:10.1016/j.jpowsour.2014.05.134 2014

  5. [5]

    Y. Zhao, L. Li, Z. Chen, C. Zheng, Z. Zhou, H. Lv, H. Wei, and Y. Wang, Multi- hierarchical heterostructure of GO/NiCo2O4/Co3O4 for high power lithium -ion batteries, J. Alloys Compd. 946 (2023) 169447 https://doi.org/10.1016/j.jallcom.2023.169447

    doi:10.1016/j.jallcom.2023.169447 2023

  6. [6]

    M. U. A. Prathap and R. Srivastava , Synthesis of NiCo 2O4 and its application in the electrocatalytic oxidation of methanol , Nano Energy 2 (2013) 1046 -1053, https://doi.org/10.1016/j.nanoen.2013.04.003

    work page doi:10.1016/j.nanoen.2013.04.003 2013

  7. [7]

    Gopalakrishnan and S

    A. Gopalakrishnan and S. Badhulika, Hierarchical Architectured Dahlia Flower-Like NiCo2O4/NiCoSe2 as a Bifunctional Electrode for High-Energy Supercapacitor and Methanol Fuel Cell Application, Energy and Fuels 35 (2021) 9646-9659, https://doi.org/10.1021/acs.energyfuels.1c00498

    work page doi:10.1021/acs.energyfuels.1c00498 2021

  8. [8]

    Joshi, L

    N. Joshi, L. F. D. Silva, H. Jadhav, J -C M Peko, B. B. M. Torres, K. Aguir, V. R. Mastelaro and O. N. Oliveira Jr , One-step approach for preparing ozone gas sensors based on hierarchical NiCo 2O4 structures, RSC Adv. 6 (2016) 92655-92662, https://doi.org/10.1039/C6RA18384K

    work page doi:10.1039/c6ra18384k 2016

  9. [9]

    H. J. Jo, A. Shit, H. S. Jhon, and S. Y. Park, Highly sensitive non -enzymatic wireless glucose sensor based on Ni –Co oxide nanoneedle -anchored polymer dots , J. Ind. Eng. Chem. 89 (2020) 485-493, https://doi.org/10.1016/j.jiec.2020.06.028

    work page doi:10.1016/j.jiec.2020.06.028 2020

  10. [10]

    X. Xu, C. Mellinger, Z. G. Cheng, X. Chen, and X. Hong, Epitaxial NiCo2 O4 film as an emergent spintronic material: Magnetism and transport properties, J. Appl. Phys. 132 16 (2022) 020901, https://doi.org/10.1063/5.0095326

    work page doi:10.1063/5.0095326 2022

  11. [11]

    X. Chen, X. Zhang, M-G Han, L. Zhang, Y. Zhu, X. Xu, and X. Hong, Magnetotransport Anomaly in Room -Temperature Ferrimagnetic NiCo2O4 Thin Films , Adv. Mater. 31 (2019) 1805260, https://doi.org/10.1002/adma.201805260

    work page doi:10.1002/adma.201805260 2019

  12. [12]

    Nogues, and I

    J. Nogues, and I. K. Schuller, Exchange bias,J. Magn. Magn. Mater. 192 (1999) 203-232, https://doi.org/10.1016/S0304-8853(98)00266-2

    doi:10.1016/s0304-8853(98)00266-2 1999

  13. [13]

    W. H. Meiklejohn , Exchange Anisotropy—A Review, J. Appl. Phys. 33 (1962) 1328- 1335, https://doi.org/10.1063/1.1728716

    work page doi:10.1063/1.1728716 1962

  14. [14]

    K. G. West, D. N. H. Nam, J. W. Lu, N. D. Bassim, Y. N. Picard, R. M. Stroud, and S. A. Wolf, Exchange bias in a single phase ferrimagnet, J. Appl. Phys. 107 (2010) 113915 (2010). http://dx.doi.org/10.1063/1.3374639

    work page doi:10.1063/1.3374639 2010

  15. [15]

    Electron

    C-Y Lin, T -C Huang, T -C Hsin, and C -F Pai, Field-Free Spin−Orbit Torque-Induced Exchange Bias Switching, ACS Appl. Electron. Mater. 7 (2025) 6655-6663, https://doi.org/10.1021/acsaelm.5c00974

    work page doi:10.1021/acsaelm.5c00974 2025

  16. [16]

    C. M. Zhu, L. G. Wang, F. C. Liu, and W. J. Kong, Exchange bias behaviors up to room temperature in NiCo 2O4/NiO nanoparticle system , Ceram. Int. 45 (2019) 9878-9883, https://doi.org/10.1016/j.ceramint.2019.02.028

    work page doi:10.1016/j.ceramint.2019.02.028 2019

  17. [17]

    D. Yang, A. Subedi, C. Liu, H. Ambaye, V. Lauter, P. A. Dowben, Y. Liu, and X. Xu, Microstructural Underpinnings of Giant Intrinsic Exchange Bias in Epitaxial NiCo 2O4 Thin Films , Adv. Electron. Mater. 11 (2025) 2400149, https://doi.org/10.1002/aelm.202400149

    work page doi:10.1002/aelm.202400149 2025

  18. [18]

    P. Li, C. Xia, D. Zheng, P. Wang, C. Jin, and H. Bai, Observation of large low -field magnetoresistance in spinel cobaltite: A new half -metal, Phys. Status Solidi RRL 10 (2016) 190-196, https://doi.org/10.1002/pssr.201510402

    work page doi:10.1002/pssr.201510402 2016

  19. [19]

    M. Kaur, P. Chand, and H. Anand, Effect of different synthesis methods on morphology and electrochemical behaviour of spinel NiCo 2O4 storage application , Inorganic Chemistry Communications 134 (2021) 108996, https://doi.org/10.1016/j.inoche.2021.108996

    work page doi:10.1016/j.inoche.2021.108996 2021

  20. [20]

    Y. Q. Wu, X. Y. Chen, P. T. Ji, Q. Q. Zhou, Sol–gel approach for controllable synthesis and electrochemical properties of NiCo2O4 crystals as electrode materials for application 17 in supercapacitors, Electrochim. Acta. 56 (2011) 7517-7522, https://doi.org/10.1016/j.electacta.2011.06.101

    work page doi:10.1016/j.electacta.2011.06.101 2011

  21. [22]

    R. Dawn, B. Pramanik, K. Das, W. W. Tjiu, Z. Aabdin, A. Ghosh, S. K. Sahoo, K. Amemiya, A. Kandasami, V. R. Singh, Origin of magnetism via cation vacancy defects in non stoichiometric NiCo2 O4 nanoparticles: A synchrotron -based x-ray absorption and x-ray magnetic circular dichroism spectroscopic study, J. Appl. Phys. 136 (2024) 143904, https://doi.org/10...

    work page doi:10.1063/5.0234829 2024

  22. [23]

    B. D. Culity and S. R. Stock, Elements of X-ray Diffraction Third ed. Pearson, Harlow, UK, 2014

    2014

  23. [24]

    Pathak, M

    P. Pathak, M. Srivastava, G. S. Bisht, and A. Srinivasan, Electrodeposited Fe2CoSn Thin Film with Enhanced Structural and Magnetic Properties, J. Electrochem. Soc. 170 (2023) 122504, https://doi.org/10.1149/1945-7111/ad155b

    work page doi:10.1149/1945-7111/ad155b 2023

  24. [25]

    M. K. Shobana, V. Rajendran, K. Jeyasubramanian, and N. S Kumar, Preparation and characterisation of NiCo ferrite nanoparticles , Mater. Lett. 61 (2007) 2616-2619, http://dx.doi.org/10.1016/j.matlet.2006.10.008

    work page doi:10.1016/j.matlet.2006.10.008 2007

  25. [26]

    Y. Y. Kannangaraa, S. Karunarathneb, W.P.S.L. Wijesinghea, C. Sandaruwana, C. R. Ratwanib, A. R. Kamalic, and A. M. Abdelkader, The electrochemical performance of various NiCo2O4 nanostructures in hybrid supercapacitors: Investigating the impact of crystalline defects , J. Energy Storage 84 (2024) 110717, https://doi.org/10.1016/j.est.2024.110717

    work page doi:10.1016/j.est.2024.110717 2024

  26. [27]

    Mishraa, P

    B. Mishraa, P . Sivaramanb, N . Shimpi, Sustainable energy storage device based on NiCo2O4 nanoflakes via one step microwave irradiation, Mater. Res. Bull. 193 (2025) 113664, https://doi.org/10.1016/j.materresbull.2025.113664

    work page doi:10.1016/j.materresbull.2025.113664 2025

  27. [28]

    Iqbal, N

    M. Iqbal, N. G. Saykar, S. K. Mahapatra, V. Kumar, and A. Arya, High-temperature supercapacitive performance of NiCo₂O₄ nanosheets: E ffect of calcination and device 18 operating temperature , Mater. Res. Bull. 194 (2026) 113724. https://doi.org/10.1016/j.materresbull.2025.113724

    work page doi:10.1016/j.materresbull.2025.113724 2026

  28. [29]

    Y.-Z. Su, Q. -Z. Xu, G. -F. Chen, H. Cheng, N. Li, and Z. -Q. Liu, One dimensionally spinel NiCo 2O4 nanowire arrays: facile synthesis, water oxidation, and magnetic properties, Electrochim. Acta 174 (2015) 1216-1224, http://dx.doi.org/10.1016/j.electacta.2015.06.092

    work page doi:10.1016/j.electacta.2015.06.092 2015

  29. [30]

    Liang, Z

    J. Liang, Z . Fan, S. Chen, S . Ding, and G . Yang, Hierarchical NiCo 2O4 Nanosheets@halloysite Nanotubes with Ultrahigh Capacitance and Long Cycle Stability As Electrochemical Pseudocapacitor Materials, Chem. Mater. 26 (2014) 4354, https://doi.org/10.1021/cm500786a

    work page doi:10.1021/cm500786a 2014

  30. [31]

    T-C Chang, Y-T Lu, C-H Lee, J. K. Gupta, L. J. Hardwick, C-C Hu, and H-Y. T. Chen, The Effect of Degrees of Inversionon the Electronic Structure of Spinel NiCo2O4: A Density Functional Theory Study, ACS Omega 6 (2021) 9692 , https://doi.org/10.1021/acsomega.1c00295

    work page doi:10.1021/acsomega.1c00295 2021

  31. [32]

    Verma, A

    S. Verma, A. Kumar, D. Pravarthana, A. Deshpande, S. B. Ogale, and S. M. Yusuf, Nearly Monodispersed Multifunctional NiCo2O4 Spinel Nanoparticles: Magnetism, Infrared Transparency, and Radiofrequency Absorption, J. Phys. Chem. C. 118 (2014) 16246, https://doi.org/10.1021/jp804923t

    work page doi:10.1021/jp804923t 2014

  32. [33]

    N. Garg, M. Basu, K. Upadhyaya, S. M. Shivaprasadb and A. K. Ganguli, Controlling the aspect ratio and electrocatalytic properties of nickel cobaltite nanorods, RSC Adv. 3, 24328 (2013), https://doi.org/10.1039/C3RA44156C

    work page doi:10.1039/c3ra44156c 2013

  33. [34]

    Ahmed M Nashaat, A. A. El -Fadl, H. Nakamura, and M. A. Kassem, Synthesis and magnetic properties of NiCo 2O4 urchin-like nanofibers, Nanotechnology 36 (2025) 085701, https://doi.org/10.1088/1361-6528/ad947f

    work page doi:10.1088/1361-6528/ad947f 2025

  34. [35]

    Mumtaza, K

    A. Mumtaza, K. Maaza, B. Janjuaa, S. K. Hasanaina, M. F. Bertinob, Exchange bias and vertical shift in CoFe2O4 nanopa rticles, J. Magn. Magn. Mater. 313 (2007) 266, https://doi.org/10.1016/j.jmmm.2007.01.007. 19

    work page doi:10.1016/j.jmmm.2007.01.007 2007

  35. [36]

    D. T. Margulies, F. T. Parker, M. L. Rudee, F. E. Spada, J. N. Chapman, P. R. Aitchison, and A. E. Berkowitz, Phys. Rev. Lett., 79 (1997) 5162, https://doi.org/10.1103/PhysRevLett.79.5162

    work page doi:10.1103/physrevlett.79.5162 1997

  36. [37]

    Joshi, S

    B. Joshi, S. Ghosh, P. Srivastava, P. Kumar and D. Kanjilal, Correlation between electrical transport, microstructure and room temperature ferromagnetism in 200 keV Ni2+ ion implanted zinc oxide (ZnO) thin films, Appl. Phys. A 107 (2012) 393 –400, https://doi.org/10.1007/s00339-012-6785-x

    work page doi:10.1007/s00339-012-6785-x 2012

  37. [38]

    L. Hu, L. Wu, M. Liao, X. Hu, and X. Fang, Electrical Transport Properties of Large, Individual NiCo 2O4 Nanoplates, Adv. Funct. Mater. 22 (2012) 998−1004 , https://doi.org/10.1002/adfm.201102155

    work page doi:10.1002/adfm.201102155 2012

  38. [39]

    W. Guo, C. Zhen, C. Wu, X. Wu, G. Li, L. Ma, and D. Hou, Influence of growth temperature on the microstructure and electrical transport properties of epitaxial NiCo2O4 thin films , Ceram. Int. 44 (2018) 12539 https://doi.org/10.1016/j.ceramint.2018.04.050

    work page doi:10.1016/j.ceramint.2018.04.050 2018

  39. [40]

    Liu and X

    Y. Liu and X. Y. Qin, Temperature dependence of electrical resistivity for Ca-doped perovskite-type Y1-xCaxCoO3 prepared by sol–gel process, J PHYS CHEM SOLIDS 67 (2006) 1893−1898, https://doi.org/10.1016/j.jpcs.2006.05.006

    work page doi:10.1016/j.jpcs.2006.05.006 2006

  40. [41]

    Sheng, B

    P. Sheng, B. Abeles, and Y. Arie, Hopping Conductivity in Granular Metals Phys. Rev. Lett. 31 (1973) 44−47, https://doi.org/10.1103/PhysRevLett.31.44

    doi:10.1103/physrevlett.31.44 1973

  41. [42]

    Getzlaff, Fundamentals of Magnetism, Springer New York (2008), ISBN-13

    M. Getzlaff, Fundamentals of Magnetism, Springer New York (2008), ISBN-13. 978- 3642068270

    2008

  42. [43]

    Ziesea, R

    M. Ziesea, R. Hö hne, H.C. Semmelhack, H. Reckentin, N.H. Hong, and P. Esquinazi, Mechanism of grain-boundary magnetoresistance in Fe3O4 films, Eur. Phys. J. B 28, 415- 422 (2002) https://doi.org/10.1140/epjb/e2002-00245-3

    work page doi:10.1140/epjb/e2002-00245-3 2002

  43. [44]

    P. Li, L. T. Zhang, W. B. Mi, E. Y. Jiang, and H. L. Bai, Origin of the butterfly-shaped magnetoresistance in reactive sputtered epitaxial Fe3O4 films, J. Appl. Phys. 106 (2009) 033908, https://doi.org/10.1063/1.3187537

    work page doi:10.1063/1.3187537 2009

  44. [45]

    K. P. McKenna, F. Hofer, D. Gilks, V. K. Lazarov, C. Chen, Z. Wang and Y. Ikuhara, Atomic-scale structure and properties of highly stable antiphase boundary defects in 20 Fe3O4, Nat. Commun. 5 (2014) 5740, https://doi.org/10.1038/ncomms6740

    doi:10.1038/ncomms6740 2014

  45. [46]

    Sarkar T., Reddy V.R., Elizabeth S., Kumar P.S.A., Antiphase boundary in antiferromagnetic multiferroic LuMn0.5Fe0.5O3: anomalous ferromagnetism, exchange bias effect and large vertical hysteretic shift, J. Phys. Condens. Matter 30 (2018) 315801. https://doi.org/10.1088/1361-648X/aacc09

    work page doi:10.1088/1361-648x/aacc09 2018