Microscopic origin of exchange bias in core/shell nanoparticles

Iglesias, Òscar; Batlle, X.; Labarta, A.

doi:10.1103/physrevb.72.212401

Cited by 126 publications

(97 citation statements)

References 33 publications

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“…The variation of the EB field can be more easily traced back to the magnetization reversal behavior of the interfacial spins at the shell [61], whose contribution to the hysteresis loop is shown in Fig. 7(b).…”

Section: Simulation Resultsmentioning

confidence: 99%

Probing core and shell contributions to exchange bias in Co/Co<inf>3</inf>O<inf>4</inf> nanoparticles of controlled size

De¹,

Iglesias

Majumdar

et al. 2017

2017 IEEE International Magnetics Conference (INTERMAG)

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Coupling at the interface of core/shell magnetic nanoparticles is known to be responsible for exchange bias (EB) and the relative sizes of core and shell components are supposed to influence the associated phenomenology. In this work, we have prepared core/shell structured nanoparticles with a total average diameter around ∼27 nm and a wide range of shell thicknesses through the controlled oxidation of Co nanoparticles well dispersed in an amorphous silica host. Structural characterizations give compelling evidence of the formation of Co 3 O 4 crystallite phase at the shells surrounding the Co core. Field cooled hysteresis loops display nonmonotonous dependence of the exchange bias H E and coercive H C fields, that become maximum for a sample with an intermediate shell thickness, at which lattice strain is also maximum for both phases. The EB effects persist up to temperatures above the ordering temperature of the oxide shell. Results of our atomistic Monte Carlo simulations of particles with the same size and composition as in experiments are in agreement with the experimental observations and have allowed us to identify a change in the contribution of the interfacial surface spins to the magnetization reversal, giving rise to the observed maximum in H E and H C .

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Section: Simulation Resultsmentioning

confidence: 99%

Probing core and shell contributions to exchange bias in Co/Co<inf>3</inf>O<inf>4</inf> nanoparticles of controlled size

De¹,

Iglesias

Majumdar

et al. 2017

2017 IEEE International Magnetics Conference (INTERMAG)

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show abstract

“…Note that for the fully dense sample, since all the nanoparticles are surrounded by several other nanoparticles, no constriction in the loop is observed [14]. Other effects such as the scatter in T SP B , o H E , and o H C values found in the literature [11,13,14,19,25,[29][30][31][32][33][34][35][36][37][38][39] could also be accounted for. Although part of the spread in results arises from the diverse core and t shell , distinctive growth methods should render dissimilar packing of the nanoparticles, which, according to the above discussion, should result in a range of values for T SP B , o H E , and o H C .…”

Section: Prl 97 157203 (2006) P H Y S I C a L R E V I E W L E T T E mentioning

confidence: 99%

Shell-Driven Magnetic Stability in Core-Shell Nanoparticles

et al. 2006

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The magnetic properties of ferromagnetic-antiferromagnetic Co-CoO core-shell nanoparticles are investigated as a function of the in-plane coverage density from 3.5% to 15%. The superparamagnetic blocking temperature, the coercivity, and the bias field radically increase with increasing coverage. This behavior cannot be attributed to the overall interactions between cores. Rather, it can be semiquantitatively understood by assuming that the shells of isolated core-shell nanoparticles have strongly degraded magnetic properties, which are rapidly recovered as nanoparticles come into contact.

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“…Because of the complex mechanisms at different kinds of interfaces, often theoretical interpretations, which are mainly based on macroscopic or phenomenological models, are inadequate. Recently, Monte Carlo simulations or micromagnetic approach [31,32,33,34,35,36,37,38] have been used to gain deeper insight into microscopic origin of EB effect. However, in most of the cases theories were limited to specific problems where intricate structures at the interfaces were simplified.…”

Section: Introductionmentioning

confidence: 99%

Exchange bias effect in alloys and compounds

Giri

Patra

Majumdar

2011

J. Phys.: Condens. Matter

321

225

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Abstract. The phenomenology of exchange bias effects observed in structurally single-phase alloys and compounds but composed of a variety of coexisting magnetic phases such as ferromagnetic, antiferromagnetic, ferrimagnetic, spin-glass, clusterglass, disordered magnetic states are reviewed. The investigations on exchange bias effects are discussed in diverse types of alloys and compounds where qualitative and quantitative aspects of magnetism are focused based on macroscopic experimental tools such as magnetization and magnetoresistance measurements. Here, we focus on improvement of fundamental issues of the exchange bias effects rather than on their technological importance.

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Microscopic origin of exchange bias in core/shell nanoparticles

Cited by 126 publications

References 33 publications

Probing core and shell contributions to exchange bias in Co/Co<inf>3</inf>O<inf>4</inf> nanoparticles of controlled size

Probing core and shell contributions to exchange bias in Co/Co<inf>3</inf>O<inf>4</inf> nanoparticles of controlled size

Shell-Driven Magnetic Stability in Core-Shell Nanoparticles

Exchange bias effect in alloys and compounds

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