Minhu Pan

Magnetization property in Ta/NiFe/Ta sandwich structure

A partial perpendicular anisotropy and a reproducible inverted minor hysteresis loop with a negative remanence were observed in Ta/NiFe/Ta. The minor inverted hysteresis loop appears only when the magnetic field is perpendicular to the film plane normal or deviates at several degrees from the normal of the film plane. This phenomenon is ascribed to the antiferromagnetic-like coupling between the co-existent minor magnetic moment with perpendicular anisotropy at the Ta/NiFe interface and major magnetic moment with in-plane anisotropy in the bulk of NiFe layer.

Study on Microstructural Characterization and Ferromagnetic Resonance in Sputtered Co/V Multilayers

The structure and magnetic properties of a series of rf sputtered ［Co(1.5nm)/V(d V )］ 20 (0.5nm≤d V ≤4nm)multilayers have been studied.The multilayers structure is found by X-ray diffraction,cross-section transmission electron microscopy,and high-resolution transmission electron microscopy to be polycrystalline with small individual columnar grains and has fairly strong fcc Co(111)and bcc V(110) texture in the film growth direction.The structural characterizations also show composition-modulated structure and severely alloyed effect.Ferromagnetic resonance measurements show relatively small g factors and 4π M eff values,which also indicates that multilayers are severely alloyed.Complicated spin wave resonance spectra were observed and analyzed.The evaluated small interlayer coupling constant shows the effect of weak exchange coupling between Co layers across V spacers.

Large change of the giant magnetoresistance behavior after changing the spacer from Cu to CuMn alloy in Co/spacer/Co structures

The giant magnetoresistance (GMR) effects in sandwiched Co/Cu/Co and Co/CuMn/Co structures have been investigated. The GMR oscillates with the spacer thickness for both cases, but is nearly antiphased. With diluted Mn atoms in the Cu spacer, the GMR curve as a function of the magnetic field changes a lot, and the saturation/switching field for GMR can be reduced greatly compared with that in Co/Cu/Co systems. This may indicate one way to obtain a highly sensitive GMR.

A study of interlayer coupling of Co/Pb multilayers

Abstract Interlayer coupling of Co/Pb multilayers was studied by magnetization and Magnetoresistance (MR) measurements and ferromagnetic-resonance (FMR). The Pb layer thickness dependence of coupling strength derived from the separation between the resonance fields of the `optical mode’ and uniform mode in perpendicular FMR spectra is consistent qualitatively with the variation of the in-plane remanence ratio and MR ratio with spacer thickness.

Concurrent variation of giant magnetoresistance and saturation Kerr rotation in NiCo/Cu multilayers

The dependences of magneto-optical effect, effective optical constants, and giant magnetoresistance (GMR) on the thickness of Cu layers were investigated in NiCo/Cu multilayers prepared by rf magnetron sputtering. A peak of saturation polar Kerr rotation θK, occurred simultaneously with that of GMR ratio when the Cu thickness is around 1.0 nm, where a clear drop of the effective optical constants n and k appeared. The peak of θK is mainly caused by the reduction of the effective optical constants, which dominate over the small drop of the effective off-diagonal elements of the dielectric tensor. The concurrent variation of GMR and θK is related to antiferromagnetic interlayer coupling, which may change the electron band structure and thus the optical and magneto-optical transitions of electrons.

Magnetooptical, optical and GMR effect in Ni–Co/Cu multilayers

Abstract A series of RF sputtered NiCo/Cu multilayers was prepared and the correlation of the interlayer coupling and magnetooptical Kerr effect (MOKE) was studied. A concurrent oscillation of the magnetoresistance ratio and the maximum Kerr rotation ( θ 2 k + η 2 k ) 1/2 with Cu layer thickness was observed. The oscillation of the Kerr rotation is attributed to changes in the band structure related to the antiferromagnetic interlayer coupling, leading to changes in the optical and magnetooptical transitions.

OSCILLATIONS OF INTERLAYER COUPLING AND MAGNETO-OPTICAL KERR EFFECT IN NICO/CU MULTILAYERS

A series of rf sputtered [NiCo(1.3 nm)/Cu(tCu)]25 multilayers with tCu=0.5–4.0 nm was prepared and the behavior of interlayer coupling, magnetoresistance, and magneto-optical Kerr effect was studied. A concurrent oscillation in the magnitude of the magnetoresistance and magneto-optical Kerr effect in visible wavelength range as a function of Cu layer thickness was observed. The changes of both the optical and magneto-optical transition due to interlayer coupling may be responsible for the magneto-optical activities.