Anomalous magnetic behavior of CuO nanoparticles

Bisht, Vijay; Rajeev, K. P.; Banerjee, S.

doi:10.1016/j.ssc.2010.01.048

Cited by 41 publications

(24 citation statements)

References 47 publications

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“…[50][51][52][53][54] The ZFC data show a peak, and the peak broadens and shifts to low temperatures on increasing the magnetic field. We analysed the nature of this peak and found that the peak temperature (T P ) as a function of field (H) does not behave as in the case of spin-glasses, cluster-glasses, 55 or superparamagnets 56,57 which indicates that the system is neither a spin-glass nor a superparamagnet. We also rule out supercooling as a possible reason for the FC-ZFC irreversibility by the following argument.…”

Section: The Fc-zfc Irreversibilitymentioning

confidence: 99%

Spin-canted magnetism and decoupling of charge and spin ordering in NdNiO3

et al. 2013

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We report detailed magnetization measurements on the perovskite oxide NdNiO3. This system has a first order metal-insulator (M-I) transition at about 200 K which is associated with charge ordering. There is also a concurrent paramagnetic to antiferromagnetic spin ordering transition in the system. We show that the antiferromagnetic state of the nickel sublattice is spin canted. We also show that the concurrency of the charge ordering and spin ordering transitions is seen only while warming up the system from low temperature. The transitions are not concurrent while cooling the system through the M-I transition temperature. This is explained based on the fact that the charge ordering transition is first order while the spin ordering transition is continuous. In the magnetically ordered state the system exhibits ZFC-FC irreversibility, as well as history-dependent magnetization and aging. Our analysis rules out the possibility of spin-glass or superparamagnetism and suggests that the irreversibility arises from magnetocrystalline anisotropy and domain wall pinning.

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Section: The Fc-zfc Irreversibilitymentioning

confidence: 99%

Spin-canted magnetism and decoupling of charge and spin ordering in NdNiO3

et al. 2013

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“…5,6 EB has been explained in terms of interaction between an AFM core and a spin glass-like or FM shell of uncompensated surface spins. 7,9,11 EB has also been observed in CuO nanowires 13 and nanostructures. 14 Differences might appear when determining the ordering temperature in nanostructured CuO based only on magnetic measurements.…”

Section: Introductionmentioning

confidence: 82%

“…Indeed, it shows a change of slope at T N and a broad maximum near 550 K 2 which has been explained in terms of a strong linear chain antiferromagnetism, along [1 0 1] direction. 3,4 CuO nanoparticles exhibit atypical properties, such as ferromagnetic (FM) response at room temperature (RT), [5][6][7][8] exchange bias (EB) phenomenon, [9][10][11][12] and variation of AFM order temperature. 9, 10 Several models have been designed to explain those findings.…”

Section: Introductionmentioning

confidence: 99%

“…It has been proposed that in CuO nanoparticles, the accumulation of oxygen vacancies weakens the super-exchange Cu-O-Cu paths inducing a T N reduction. 7,8 Ferromagnetic behavior has been attributed to uncompensated surface spins 7,9,11 and to oxygen vacancies causing mixed valence systems. 5,6 EB has been explained in terms of interaction between an AFM core and a spin glass-like or FM shell of uncompensated surface spins.…”

Section: Introductionmentioning

confidence: 99%

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Magnetic hardness features and loop shift in nanostructured CuO

Bianchi

Stewart

Zysler

et al. 2012

Journal of Applied Physics

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Enhanced magnetic behavior, exchange bias effect, and dielectric property of BiFeO3 incorporated in (BiFeO3)0.50 (Co0.4Zn0.4Cu0.2 Fe2O4)0.5 nanocomposite AIP Advances 4, 037112 (2014); 10.1063/1.4869077 Core/shell magnetism in NiO nanoparticles J. Appl. Phys. 114, 083906 (2013); 10.1063/1.4819807 Structural and room-temperature ferromagnetic properties of Fe-doped CuO nanocrystalsNanostructures of cupric oxide (CuO) obtained by ball milling show drastic changes in its magnetic behavior that cannot be only associated to a size effect. While sample of average size D ¼ 29 nm presents a magnetic behavior that resembles that of bulk material with a N eel temperature of 195 K, another sample with D ¼ 24 nm displays a departure from the magnetic features typical of bulk CuO and has magnetic hardness characteristics at low temperatures. Both samples show irreversibility above room temperature and shifts in their hysteresis loops along magnetization and field axis when field cooled in a H FC ¼ 50 kOe to 10 K. At this temperature, an apparent exchange bias like field, "H EB ", 0.17 and 1.06 kOe were estimated for 29 and 24 nm CuO samples, respectively. Magnetic behavior differences observed in samples subjected to distinct milling times are explained as due to a proposed model for milled CuO consisting of a multilayer configuration where interfaces comprise uneven structural disorder and oxygen deficiencies, which generate a peculiar antiferromagnetic/ferromagnetic interface configuration. V C 2012 American Institute of Physics. [http://dx.

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“…For example, NiO nanoparticles have been reported to show spin glass like behavior; 6,12 CuO nanoparticles show an anomalous magnetic behavior that cannot be described as superparamagnetic or spin glass like; 22 Ferritin shows superparamagnetic behavior 8,23 etc. Co 3 O 4 is an antiferromagnetic material and in the bulk form, its Néel temperature has been reported to lie between 30 K and 40 K. 24 There have been some reports on hysteresis, time dependence of magnetization, exchange bias and finite size effects in bare, coated and dispersed Co 3 O 4 nanoparticles and various claims have been made in support of spin glass like and superparamagnetic behavior in these particles.…”

Section: 19-21mentioning

confidence: 99%

Non-equilibrium effects in the magnetic behavior of Co3O4 nanoparticles

Bisht

Rajeev

2011

Solid State Communications

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We report detailed studies on non-equilibrium magnetic behavior of antiferromagnetic Co3O4 nanoparticles. Temperature and field dependence of magnetization, wait time dependence of magnetic relaxation (aging), memory effects and temperature dependence of specific heat have been investigated to understand the magnetic behavior of these particles. We find that the system shows some features characteristic of nanoparticle magnetism such as bifurcation of field cooled (FC) and zero field cooled (ZFC) susceptibilities and a slow relaxation of magnetization. However, strangely, the temperature at which the ZFC magnetization peaks coincides with the bifurcation temperature and does not shift on application of magnetic fields up to 1 kOe, unlike most other nanoparticle systems. Aging effects in these particles are negligible in both FC and ZFC protocol and memory effects are present only in FC protocol. We estimate the Néel temperature by using Fisher's relation as well as directly by measurement of specific heat, thus testing the validity of Fisher's relation for nanoparticles. We show that Co3O4 nanoparticles constitute a unique aniferromagnetic system which develops a magnetic moment in the paramagnetic state because of antiferromagnetic correlations and enters into a blocked state above the Néel temperature.

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Anomalous magnetic behavior of CuO nanoparticles

Cited by 41 publications

References 47 publications

Spin-canted magnetism and decoupling of charge and spin ordering in NdNiO3

Spin-canted magnetism and decoupling of charge and spin ordering in NdNiO3

Magnetic hardness features and loop shift in nanostructured CuO

Non-equilibrium effects in the magnetic behavior of Co3O4 nanoparticles

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