Study on anomalous magnetoresistance in nano-Fe3O4/Ag granular system

Kimishima, Y.; Yamada, W.; Uehara, M.; Asaka, Toru; Kimoto, Koji; Matsui, Yoshio

doi:10.1016/j.mseb.2007.01.019

Cited by 11 publications

(9 citation statements)

References 14 publications

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“…Here E 1 , E 2 and E 3 are respectively, the energy differences between the ground 6 A 1g and the crystalfield excited 4 T 1 [t 4 2 ( 3 T 1 )e], 4 T 1 [t 3 2 ( 2 T 2 )e 2 ( 3 A 2 )] and 4 T 1 [t 2 2 ( 3 T 1 )e 3 ] states. They can be expressed in terms of the cubic field parameter D q and the Racah parameters B and C for the 3d 5 ion in crystals: E 1 ≈ 10B +6C −10D q, E 2 ≈ 19B +7C and E 3 ≈ 10B +6C +10D q. E n and E a are those between the ground 6 A 1g and the charge transfer excited 6 T n 1 and 6 T a 1 states, which are obtained from the empirical relationships…”

Section: Calculations For the G Factormentioning

confidence: 99%

“…Silver halides (AgX, with X=Cl and Br) containing iron (e.g., Fe 3+ ) have interesting electrochemical [1,2], magnetic [3,4], photocatalytic [5] and structural [6] properties and attract extensive attention of researchers. It is well known that these properties are closely related to the electronic states and local structures of the impurity ions in the hosts, which may be studied by means of electron paramagnetic resonance (EPR) technique.…”

Section: Introductionmentioning

confidence: 99%

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Investigations of the EPR parameters for the tetrahedral [FeX_4]^- clusters in AgX (X=Cl, Br)

Song¹,

Wu²,

Kuang³

et al. 2012

Condens. Matter Phys.

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The EPR parameters g factors and the superhyperfine parameters for the tetrahedral [FeX 4 ] − clusters in AgX (X = Cl, Br) are theoretically investigated from the perturbation formulas of these parameters for a 3d 5 ion under tetrahedra by considering both the crystal-field and charge transfer contributions. The related model parameters are quantitatively determined from the cluster approach in a uniform way. The g -shift △g (= g −g s , where g s ≈ 2.0023 is the spin only value) from the charge transfer contribution is opposite (positive) in sign and much larger in magnitude as compared with that from the crystal-field one. The importance of the charge transfer contribution increases rapidly with increasing the covalency and the spin-orbit coupling coefficient of the ligand and thus exhibits the order of AgCl < AgBr. The unpaired spin densities of the halogen ns, npσ and npπ orbitals are quantitatively determined from the related molecular orbital coefficients based on the cluster approach.

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Section: Calculations For the G Factormentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Investigations of the EPR parameters for the tetrahedral [FeX_4]^- clusters in AgX (X=Cl, Br)

Song¹,

Wu²,

Kuang³

et al. 2012

Condens. Matter Phys.

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“…During electroless deposition, it is very difficult for large quantities of Ag atoms and Fe 3 O 4 molecules to dope and/or diffuse into each other. [20][21][22] Therefore, it can be inferred that the as-synthesized Fe 3 O 4 -Ag nanoparticles have a core-shell structure with Fe 3 O 4 as the core and Ag as the shell. This was verified by HRTEM.…”

Section: Mechanism Of Electroless Deposition Of Ag On the Surface Of mentioning

confidence: 99%

Magnetic Silver-Coated Ferrite Nanoparticles and Their Application in Thick Films

Liu

Huang

et al. 2010

Journal of Elec Materi

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Magnetic silver-coated ferrite nanoparticles with 39.8% weight gain (relative to ferrite nanopowder coated by a silver layer) were synthesized by electroless deposition of silver on ferrite nanopowder. The mechanism of the electroless deposition was explored in terms of pretreatment, sensitization, activation, and the reduction of silver-ammonia complexes. Experiments showed that the optimal deposition conditions were a temperature of 50°C, pH value of 10 to 12, duration of 65 min with ethanol plus polyethylene glycol as additives, and ultrasonic vibration as a method of dispersing the nanoparticles. From transmission electron microscopy (TEM) images, it was observed that as-synthesized nanoparticles had a core-shell structure with a particle size of 35 nm to 90 nm and a shell thickness of 5 nm to 20 nm. X-ray diffraction (XRD) analysis confirmed that only ferrite and metallic silver were present in the product. Electrical resistance and magnetic hysteresis measurements demonstrated that the nanoparticles were both electrically conductive (volume electrical resistivity on the order of 10 À4 X cm to 10 À3 X cm when compressed to pressure of 2 9 10 6 Pa) and possessed ferrimagnetic properties. After a thick-film paste, obtained with the nanoparticles as the functional phase, was directly written and sintered, scanning electron microscopy (SEM) analysis and electrical resistance measurements of conductive lines in the acquired array pattern showed that an electrically conductive network with some defects and cavities was formed, with a volume electrical resistivity of 1 9 10 À4 X cm to 1 9 10 À3 X cm.

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“…First, the precursors of Fe 3 0 4 nano-particles were prepared from a mixed aqueous solution of FeC1 2 •4H 2 0 and FeC1 3 •6H 2 0 with the mole ratio of 1:2. When an aqueous ammonium solution (NH 4 0H) was dripped onto the above mixed solution, Fe 3 0 4 nano-particles with a diameter of about 10 nm were precipitated [10][11][12]. Washed and dried Fe 3 0 4 nano-particles were pressed to form pellets with a diameter of 10 mm, and sintered in the NH 3 +H 2 mixed gases for 12 hours at 673 K. Then the mixtures of prepared y '-Fe 4 N specimen and MgO powder were sintered at 473K for 3 hours in air.…”

Section: Sample Preparationmentioning

confidence: 99%

Tunneling Magneto-Resistance Effect of Fe<sub>4</sub>N with MgO Barrier

Kimishima¹,

Homma²,

Uehara³

et al. 2008

Trans. Mat. Res. Soc. Japan

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y '-Fe4N is the ferromagnetic material with high Curie temperature and relatively high electrical conductivity. First principle calculation showed that they '-Fe 4 N was a half-metal by 100% spin polarized conduction electrons with minority spins. So we expected large tunneling magneto-resistance effect in the Fe4N/MgO/Fe 4 N junctions. y '-Fe 4 N was prepared by sintering Fe 3 0 4 nanoparticles in the atmosphere of NH 3 /H 2 gas mixture at 673 K. Then MgO was added to the y '-Fe 4 N powder and sintered at about 473 K in pure Ar gas. Magneto-resistance was measured by 4-terminals method for x=0-0.8 samples of (MgO)x(Fe 4 N) 1 _x, and magneto-resistance ratios of-1.2~-1 % were observed for x=0.3~0.6 samples at 300K. It is the first observation oftunneling magneto-resistance effect fory '-Fe 4 N granular system.

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Study on anomalous magnetoresistance in nano-Fe3O4/Ag granular system

Cited by 11 publications

References 14 publications

Investigations of the EPR parameters for the tetrahedral [FeX_4]^- clusters in AgX (X=Cl, Br)

Investigations of the EPR parameters for the tetrahedral [FeX_4]^- clusters in AgX (X=Cl, Br)

Magnetic Silver-Coated Ferrite Nanoparticles and Their Application in Thick Films

Tunneling Magneto-Resistance Effect of Fe<sub>4</sub>N with MgO Barrier

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