Zhan Wen-Shan

Bulk-like contribution to tunnel magnetoresistance in magnetic tunnel junctions

We have demonstrated that the bulk-like contribution to tunnelling magnetoresistance (TMR) exists in the magnetic tunnel junctions and is determined by the tunnelling characteristic length of the ferromagnetic electrodes. In the experiment, a wedge-shaped CoFe layer is inserted at the interface between the insulating barrier and the reference electrode. It is found that TMR ratio increases from 18% without CoFe layer to a saturation value of 26.5% when the CoFe thickness is about 2.3 nm. The tunnelling characteristic length, ltc, can be obtained to be about 0.8 nm for CoFe materials.

Magnetic Anisotropy in the Radula of Chiton

Radular teeth of chitons were studied by using magnetic torque-meter and transmission electron microscopy (TEM). The magnetic torque curves give clear evidence of presence of strong uni-axial magnetic anisotropy. The easy axis is along the length direction of tongue-like radula. The TEM pattern shows that long chip-like magnetite nano-scaled particles packed in the radular teeth with both uni-axial shape anisotropy and magneto-crystalline anisotropy.

Spin-Flip Behaviour Observed in (Pt/Co)5/Ru/(Co/Pt)5 Films

(Pt/Co)5/Ru/(Co/Pt)5 films with different Ru thicknesses were prepared by magnetron sputtering. Oscillatory behaviour of effective perpendicular anisotropy and remanence in the (Pt/Co)5/Ru/(Co/Pt)5 films as a function of the thickness of Ru has been first observed, from which we can obtain the conclusion that the synthetic spin in the (Pt/Co)5/Ru/(Co/Pt)5 films rotates from the vertical direction to the in-plane one periodically with the change of the thickness of the spacer layer of Ru. The oscillatory period is about two atomic layers of Ru and different from the long and short oscillatory periods of the interlayer antiferromagnetic coupling in Co/Ru/Co, Co/Cu/Co, and Fe/Cr/Fe, etc.

Magnetoresistance and magnetic properties of Fe3O4 nanoparticle compacts

In this paper, we report on the magnetic properties of Fe3O4 nanoparticles with different grain sizes under different pressures. In all the samples, the saturated magnetization Ms shows a linear decrease with increasing pressure. The thickness of the magnetic dead layer on the nanoparticle surface under different pressures was roughly estimated, which also increases with increasing pressure. The transport measurements of the nanoparticle Fe3O4 compacts show that the low-field magnetoresistance (MR) value is insensitive to the grain size in a wide temperature range; however, the high-field MR value is dependent on grain size, especially at low temperatures. These experimental results can be attributed to the different surface states of the nanoparticles.

Electrical resistance of Fe100−xBx metallic glass system under pressure (12≤x≤24)

Abstract The variation of resistance with hydrostatic pressure has been measured for the Fe100−xBx metallic glass system (12≤x≤24) in the range 0–8 Kbar and at room temperature. In all of the alloys the pressure coefficients of resistance α p (= dlnR dP ) are negative; the αp versus x show an abrupt fall from x=12 to 20, and they are nearly independent of x for 20≤x≤24.

Origin of ultraviolet photovoltaic effect in Fe3O4 thin films

We have investigated the transport and ultraviolet photovoltaic properties of Fe3O4 thin films grown on glass substrates by facing-target sputtering technique. The nonlinear dependence of current-density on voltage suggests that the transport process is most likely the tunnelling process and grain boundaries act as barriers. Furthermore, nonequilibrium electron-hole pairs are excited in the grains and grain boundary regions for Fe3O4 film under ultraviolet laser, since the energy gap of Fe3O4 is smaller than the ultraviolet photon energy. And then the built-in electric field near the grain boundaries will separate carriers, leading to the appearance of an instant photovoltage.

The effect of Pd doped in Ru layer on the interlayer coupling in Co/RuPd multilayers

2.0nmCo/tnmRu1−xPdx multilayers with x=0, 0.05, 0.08, 0.24, 0.39 and 0.48 were prepared by magnetron sputtering. The spacer layer thickness of both Ru (before doping Pd) and RuPd (after doping Pd) varies from 0.2nm to 1.6nm. Two effects have been investigated: (1) the dependence of the interlayer coupling on the thickness of Ru1−xPdx as a function of x and (2) the dependence of the interlayer coupling on Pd doping density, x, as a function of thickness of Ru1−xPdx. Our results indicate that the interlayer coupling is strongly dependent on the doping density and the spacer layer thickness. The saturation field Hs increases when very low concentration of Pd doped in the Ru layers and a suitable spacer thickness are adopted.

Percolation-related magnetic coupling and magnetoresistance properties in Fe/Si1-xAgx multilayers

In this paper, we present a study of the magnetic coupling and magnetoresistance (MR) properties in Fe/Si1-xAgx multilayers with a granular Si1-xAgx spacer layer. We have found that, with increasing silver content (x) in a silicon matrix, the magnetic state of multilayers changes from a nonmagnetic coupling state to weak antiferromagnetic around the percolation point of the ~2.4 nm thick spacer Si1-xAgx. The MR measurements also reveal an abrupt increase of MR near the same percolation point. These changes are ascribed to the formation of the percolation path in the granular spacer.

Interface Effects on the Magneto-Optical Kerr Effect and Optical Properties in Co/Ni Multilayer

The influence of interfaces on the magneto-optical Kerr effect in the Co/Ni multilayer has been investigated. It was found that the magnetic-optical Kerr rotation varies with the numbers of interfaces (x) in the Co/Ni multilayer, which indicated that the interface states play an important role in the Kerr effect. Moreover, ellipticity and optical constants n and k are also found to vary with x. Some possible mechanisms have been discussed.