Giant Room-Temperature Magnetoresistance in PolycrystallineZn0.41Fe2.59O4

Abstract

A tunneling-type magnetoresistance (MR) as large as 158% is observed at T = 300 K in a polycrystalline Zn0.41Fe2.59O4 sample, in which the Zn0.41Fe2.59O4 grains are separated by insulating alpha-Fe2O3 boundaries. The huge room-temperature MR is attributed to the high spin polarization of Zn(0.41)Fe(2.59)O4 grains and antiferromagnetic correlations between magnetic domains on both sides of the insulating alpha-Fe2O3 boundary. The MR exhibits strong temperature dependence below 100 K and its magnitude is enhanced to reach 1280% at 4.2 K, which may arise from the Coulomb blockade effect.

Electrical and magnetoresistance properties of composites consisting of iron nanoparticles within the hexaferrites

“…22 We find similar observations for the present composites. At the controlled reduction condition where metal-to-insulator changeover is observed (e.g., M-R400/45 min), the insulator regime exhibits large MR compared to the metallic regime.…”

Large grain-boundary magnetoresistance in MnFe2O4 nanoparticle compact

“…This is because that magnetite is a good candidate to show the required properties for application due to its high Curie temperature and half metallic behavior [2,11]. While few reports were found in other ferrites, for example, giant MR were found in Zn 1Àx Ni x Fe 2 O 4 and (ZnFe) 3 O 4 -a-Fe 2 O 3 ceramic [12,13]. In our previous work, we have synthesized various monodisperse ferrites of 200-800 nm [14], and found enhanced LFMR of about 10% at RT in the compact of Fe 3 O 4 nanoparticles of 200 nm [9].…”

“…In most cases, the grain boundary has been treated as an insulating barrier across which a spin-polarized tunneling of conducting electrons occurs. Till now, a lot of work has been carried out in a hope to optimize the devices to have a room temperature (RT) MR effect competitive with the giant MR multilayers [2][3][4][5][6][7][8][9][10][11][12][13]. However, a large MR could usually be obtained at high magnetic field or low temperature in the grain-boundary systems.…”

Magnetoplumbite and W-type barium ferrites as magnetic mixture with hematite

“…This type of MR has been reported in polycrystalline films 2)-5) and also in sintered compacts. 6), 7) Most of their combinations were ferromagnetic metals with nonmagnetic oxide insulator. There is a big advantage in oxide combinations to reduce their interface reaction in their preparation and also in their operation.…”