Tunnel magnetoresistance and magnetic ordering in ion-beam sputtered Co80Fe20/Al2O3 discontinuous multilayers

Kakazei, G. N.; Pogorelov, Yu. G.; Lopes, A. M. L.; Sousa, J.B.; Cardoso, S.; Freitas, P. P.; Azevedo, M.M. Pereira de; Snoeck, E.

doi:10.1063/1.1399029

Cited by 82 publications

(77 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The sample, [Co 80 Fe 20 (t n =0.9nm)/Al 2 O 3 (3 nm)] 10 , was prepared by Xe-ion-beam sputtering on a glass substrate [14]. High-resolution transmission electron microscopy (HRTEM) images on a related sample with nominal CoFe thickness, t n =1.3 nm, reveal that the CoFe forms isolated quasispherical nanoparticles of average diameter d ≈ 3 nm and a log-normal size distribution width σ ≈ 2.7.…”

Section: Methodsmentioning

confidence: 99%

Magnetic relaxation phenomena in the superspin-glass system [Co80Fe20/Al2O3]10

Sahoo¹,

Petracic²,

Binek³

et al. 2002

J. Phys.: Condens. Matter

View full text Add to dashboard Cite

Relaxation and temperature cycles of thermoremanent magnetization, M TRM , in the superspin-glass phase of [Co 80 Fe 20 (0.9 nm)/Al 2 O 3 (3 nm)] 10 have been investigated. The relaxation of M TRM exhibits ageing phenomena. In negative temperature cycles for temperature steps larger than 1 K the magnetic state is retrieved (memory effect) on returning to the measurement temperature. This property is independent of the application of a fi eld step during intermediate cooling. In positive temperature cycles the relaxation is suppressed after temporary heating. The observations are discussed in the light of both the droplet and the hierarchical picture.

show abstract

Section: Methodsmentioning

confidence: 99%

Magnetic relaxation phenomena in the superspin-glass system [Co80Fe20/Al2O3]10

Sahoo¹,

Petracic²,

Binek³

et al. 2002

J. Phys.: Condens. Matter

View full text Add to dashboard Cite

show abstract

“…The samples were prepared by sequential Xe-ion beam sputtering from Co 80 Fe 20 and Al 2 O 3 targets on glass substrates [18]. Due to the nonwetting properties of the soft FM Co 80 Fe 20 , it grows as an ensemble of nearly spherical particles being eventually embedded in the insulating Al 2 O 3 matrix.…”

Section: Details Of Experiments and Simulationmentioning

confidence: 99%

Collective states of interacting ferromagnetic nanoparticles

Petracic

Chen

Bedanta

et al. 2006

Journal of Magnetism and Magnetic Materials

Self Cite

163

129

View full text Add to dashboard Cite

Discontinuous magnetic multilayers [CoFe/Al 2 O 3 ] are studied by use of magnetometry, susceptometry and numeric simulations. Soft ferromagnetic Co 80 Fe 20 nanoparticles are embedded in a diamagnetic insulating a-Al 2 O 3 matrix and can be considered as homogeneously magnetized superspins exhibiting randomness of size (viz. moment), position and anisotropy. Lacking intra-particle core-surface ordering, generic freezing processes into collective states rather than individual particle blocking are encountered. With increasing particle density one observes first superspin glass and then superferromagnetic domain state behavior. The phase diagram resembles that of a dilute disordered ferromagnet. Criteria for the identification of the individual phases are given.

show abstract

“…Discussion.-Past experimental studies of selfassembled ferromagnetic arrays were dealing either with their thermodynamic properties [1,2,3,4], or with domain wall motion [26]. Investigations of the electronic transport and magnetoresistance (MR) were mostly restricted to the SPM state [27,28], where variable range hopping was observed. The crossover region near T s c was only studied by numerical methods in the context of manganite systems [5,9,10].…”

mentioning

confidence: 99%

Electron Transport in Nanogranular Ferromagnets

2007

View full text Add to dashboard Cite

We study electronic transport properties of ferromagnetic nanoparticle arrays and nanodomain materials near the Curie temperature in the limit of weak coupling between the grains. We calculate the conductivity in the Ohmic and non-Ohmic regimes and estimate the magnetoresistance jump in the resistivity at the transition temperature. The results are applicable for many emerging materials, including artificially self-assembled nanoparticle arrays and a certain class of manganites, where localization effects within the clusters can be neglected.PACS numbers: 73.43.Qt Arrays of ferromagnetic nanoparticles are becoming one of the mainstreams of current mesoscopic physics [1,2,3,4]. Not only ferromagnetic granules promise to serve as logical units and memory storage elements meeting elevated needs of emerging technologies, but also offer an exemplary model system for investigation of disordered magnets. At the same time the model of weakly coupled nanoscale ferromagnetic grains proved to be useful for understanding the transport properties of doped manganite systems [5,6] that have intrinsic inhomogeneities. Recent studies showed that above the Curie temperature these materials possess a nanoscale ferromagnetic cluster structure which to a large extend controls transport in these systems [7,8,9,10]. This defines an urgent quest for understanding and quantitative description of electronic transport in ferromagnetic nanodomain materials based on the model of nanogranular ferromagnets.In this paper we investigate electronic transport properties of arrays of ferromagnetic grains [11] near the ferromagnetic-paramagnetic transition, see Fig. 1. At low temperatures, T < T s c , the sample is in a so called superferromagnetic (SFM) state, see Fig. 1, set up by dipole-dipole interactions. Near the macroscopic Curie temperature, T s c , thermal fluctuations destroy the macroscopic ferromagnetic order. At intermediate temperatures T s c < T < T g c , where T g c is the Curie temperature of a single grain, the system is in a superparamagnetic (SPM) state where each grain has its own magnetic moment while the global ferromagnetic order is absent. At even higher temperatures, T > T g c , the ferromagnetic state within each grain is destroyed and the complete sample is in a paramagnetic state. We consider the model of weakly interacting grains in which the sample Curie temperature is much smaller than the Curie temperature of a single grain, T s c ≪ T g c . We first focus on the SPM state, and discuss a d−dimensional array (d = 3, 2) of ferromagnetic grains taking into account Coulomb interactions between electrons. Granularity introduces additional energy parameters apart from the two Curie temperatures, T g c and T s c : each nanoscale cluster is characterized by (i) the charging c , where T s c is the macroscopic Curie temperature of the system, the ferromagnetic grains (superspins) form a superferromagnet (SFM); for T s c < T < T g c , where T g c is the Curie temperature for a single grain, the system is in a superparamagne...

show abstract

Tunnel magnetoresistance and magnetic ordering in ion-beam sputtered Co80Fe20/Al2O3 discontinuous multilayers

Cited by 82 publications

References 16 publications

Magnetic relaxation phenomena in the superspin-glass system [Co80Fe20/Al2O3]10

Magnetic relaxation phenomena in the superspin-glass system [Co80Fe20/Al2O3]10

Collective states of interacting ferromagnetic nanoparticles

Electron Transport in Nanogranular Ferromagnets

Contact Info

Product

Resources

About