Giant exchange bias and exchange enhancement observed in CoFe2O4-based composites

Zan, Fenlian; Ma, Yongqing; Ma, Qian; Xu, Yuanfeng; Dai, Zhaoxin; Zheng, Ganhong

doi:10.1016/j.jallcom.2013.07.062

Cited by 14 publications

(4 citation statements)

References 46 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Note that measured value of µ 0 H E = 365 mT on the composite particles is significantly higher than the best values recently reported on oxide‐based granular composites called “giant exchange‐bias” systems, like NiFe 2 O 4 ‐CoO, SrFe 12 O 19 @CoO, CoFe 2 O 4 @Co 3 O 4, and others summarized in Table SI‐1 in the Supporting Information. These results are very promising and make our engineered CFO‐CO composites particularly valuable as starting powder for the production of exchange‐biased oxide‐based consolidates.…”

Section: Resultsmentioning

confidence: 56%

“…In addition, EB has been observed in a variety of ferromagnetic metals and ferrimagnetic oxides. Focusing on oxides, it was reported in double perovskites, manganites, cobaltites, garnets, hexaferrites, and spinel ferrites . For most of these systems, a shift and a broadening of the hysteresis loops were observed in magnetic field cooling operating conditions.…”

Section: Introductionmentioning

confidence: 99%

“…For most of these systems, a shift and a broadening of the hysteresis loops were observed in magnetic field cooling operating conditions. As significant they are as the crystallographic coherence between the contacted F and AF phases, their good size proportion and their optimized weight ratio are achieved, making some authors calling certain oxide‐based granular composites as “giant exchange bias” systems, like SrFe 12 O 19 @CoO and CoFe 2 O 4 @Co 3 O 4 ones. All these previous studies underline the importance of the chemical nature of the involved F and AF phases in EB onset.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Giant Exchange‐Bias in Polyol‐Made CoFe₂O₄‐CoO Core–Shell Like Nanoparticles

Flores‐Martínez

Franceschin

Gaudisson

et al. 2018

Part & Part Syst Charact

View full text Add to dashboard Cite

Cobalt ferrite ferrimagnetic nanoparticles (NPs) are prepared and used in this work as seeds to grow a thin antiferromagnetic poly‐ and nanocrystalline CoO shell. The major purpose is to study systematically the characteristics of the as‐produced powders, making emphasis on their internal crystallographic arrangement and their magnetic properties. 57Fe Mössbauer spectrometry evidences an evolution of the cation distribution among the spinel lattice in the cobalt ferrite core during the core–shell NPs processing. High‐resolution transmission electron microscopy shows a perfect epitaxy between the face‐centered cubic lattices of the spinel core and the rock‐salt shell. Finally, the measurements of 7T‐field‐cooled magnetic hysteresis loops at low temperature (5 K) of the composite particles exhibit a strong exchange bias coupling with an exchange field, µ0HE, of 365 mT and an enhanced coercive field, µ0HC, of 1395 mT. These values are very high compared to those of differently prepared CoO‐based oxide composite NPs and for which a giant exchange‐bias is reported. These features are attributed to the favorable material processing conditions offered by the polyol process in terms of crystalline quality, particularly at the interfaces, and for the pinning action exerted by the CoO phase on the magnetization of the CoFe2O4 phase.

show abstract

Section: Resultsmentioning

confidence: 56%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Giant Exchange‐Bias in Polyol‐Made CoFe₂O₄‐CoO Core–Shell Like Nanoparticles

Flores‐Martínez

Franceschin

Gaudisson

et al. 2018

Part & Part Syst Charact

View full text Add to dashboard Cite

show abstract

“…[1][2][3][4][5][6][7] Furthermore, theoretically nanoscale magnetic materials provide a highly controlled experimental system to study fundamental physics phenomena. 7,[8][9][10][11][12][13][14] One member of the magnetic material family, cobalt ferrite (CoFe 2 O 4 ), is very attractive because of its high saturation magnetization (M s ) and magnetic anisotropy, which give rise to desirable magnetic behavior at room temperature. 15,16 Some of the novel behavior of nanoscale magnetic materials is derived from the finite size effects that occur in particles with dimensions up to 100 nm.…”

Section: Introductionmentioning

confidence: 99%

Simultaneous effects of surface spins: rarely large coercivity, high remanence magnetization and jumps in the hysteresis loops observed in CoFe₂O₄nanoparticles

Zheng

et al. 2015

Nanoscale

View full text Add to dashboard Cite

Well-dispersed uniform cobalt ferrite nanoparticles were synthesized by thermal decomposition of a metal-organic salt in organic solvent with a high boiling point. Some of the nanoparticles were diluted in a SiO2 matrix and then the undiluted and diluted samples were characterized and their magnetic behavior explored. The undiluted and diluted samples exhibited maximum coercivity Hc of 23,817 and 15,056 Oe at 10 K, respectively, which are the highest values reported to date, and the corresponding ratios of remanence (Mr) to saturation (Ms) magnetization (Mr/Ms) were as high as 0.85 and 0.76, respectively. Interestingly, the magnetic properties of the samples changed at 200 K, which was observed in magnetic hysteresis M(H) loops and zero-field cooling curves as well as the temperature dependence of Hc, Mr/Ms, anisotropy, dipolar field, and the magnetic grain size. Below 200 K, both samples have large effective anisotropy, which arises from the surface spins, resulting in large Hc and Mr/Ms. Above 200 K, the effective anisotropy decreases because there is no contribution from surface spins, while the dipolar interaction increases, resulting in small Hc and Mr/Ms. Our results indicate that strong anisotropy and weak dipolar interaction tend to increase Hc and Mr/Ms, and also clarify that the jumps around H = 0 in M(H) loops can be attributed to the reorientation of surface spins. This work exposes the underlying mechanism in nanoscale magnetic systems, which should lead to improved magnetic performance.

show abstract

Separated CoFe2O4/CoFe nanoparticles by the SiO x matrix: revealing the intrinsic origin for the small remanence magnetization

Geng

et al. 2015

J Nanopart Res

View full text Add to dashboard Cite

In order to clarify the intrinsic reason for the smaller remanence (M r )-to-saturation (M s ) magnetization ratio M r /M s than that expected by the Stoner-Wohlfarth model in CoFe 2 O 4 /CoFe 2 nanoparticles in the previous report, we first prepared welldispersed CoFe 2 O 4 nanoparticles, and then they were diluted in the SiO 2 matrix followed by reduction in H 2 as far as possible to exclude or reduce disadvantageous variables (such as the growth and aggregation of particles and the exchange coupling between soft magnetic particles in the process of reducing) affecting magnetic properties. Such an idea has not been taken into account before to our knowledge. The analyses on the magnetic results indicate that the CoFe 2 O 4 /CoFe 2 nanoparticles herein reported are a pure dipolar system, in which the coercivity (H c ) and M r /M s ratio are very sensitive to the anisotropy and the strength of dipolar interaction. These results signify that it is important to maintain the CoFe 2 O 4 /CoFe 2 nanoparticles with higher anisotropy and weaker dipolar interaction for improving M r /M s and H c . This suggestion was further confirmed by our another result wherein an M r /M s value of 0.64 was obtained even though no exchange coupling was observed in the CoFe 2 O 4 /CoFe 2 nanoparticles, and further work is in process.

show abstract

Giant exchange bias and exchange enhancement observed in CoFe2O4-based composites

Cited by 14 publications

References 46 publications

Giant Exchange‐Bias in Polyol‐Made CoFe₂O₄‐CoO Core–Shell Like Nanoparticles

Giant Exchange‐Bias in Polyol‐Made CoFe₂O₄‐CoO Core–Shell Like Nanoparticles

Simultaneous effects of surface spins: rarely large coercivity, high remanence magnetization and jumps in the hysteresis loops observed in CoFe₂O₄nanoparticles

Separated CoFe2O4/CoFe nanoparticles by the SiO x matrix: revealing the intrinsic origin for the small remanence magnetization

Contact Info

Product

Resources

About

Giant exchange bias and exchange enhancement observed in CoFe2O4-based composites

Cited by 14 publications

References 46 publications

Giant Exchange‐Bias in Polyol‐Made CoFe2O4‐CoO Core–Shell Like Nanoparticles

Giant Exchange‐Bias in Polyol‐Made CoFe2O4‐CoO Core–Shell Like Nanoparticles

Simultaneous effects of surface spins: rarely large coercivity, high remanence magnetization and jumps in the hysteresis loops observed in CoFe2O4nanoparticles

Separated CoFe2O4/CoFe nanoparticles by the SiO x matrix: revealing the intrinsic origin for the small remanence magnetization

Contact Info

Product

Resources

About

Giant Exchange‐Bias in Polyol‐Made CoFe₂O₄‐CoO Core–Shell Like Nanoparticles

Giant Exchange‐Bias in Polyol‐Made CoFe₂O₄‐CoO Core–Shell Like Nanoparticles

Simultaneous effects of surface spins: rarely large coercivity, high remanence magnetization and jumps in the hysteresis loops observed in CoFe₂O₄nanoparticles