Peng Chubing

Magnetic properties of FexCu1−x granular alloy films

The magnetic properties of the FexCu1−x granular system, as functions of iron particle size, were studied. Using high resolution transmission electron microscopy, iron particle size was determined to be ranged from 1–4 nm in as‐deposited samples as x=0.06–0.34. Magnetic measurements revealed that samples exhibit superparamagnetic relaxation below 300 K as x≤0.22. At 1.5 K, the average magnetic moment per each iron atom is reduced as the average number N of iron atoms in a particle is less than 450, and approaches the value of bulk iron as N≥600. Moreover, the temperature dependence of magnetization for Fe–Cu granular alloys was found to obey the Bloch’s T3/2 law below 300 K as x≳0.22. We suggest that spin wave excitations of long wavelength occur due to the weak exchange coupling among iron particles as x≳0.22. This behavior was confirmed by the ferromagnetic resonance study.

Interlayer exchange coupling study of Ni80Fe20/Cr multilayered structures

Abstract The evidences of antiferromagnetic interlayer exchange coupling in Ni80Fe20/Cr multilayered structures were reported. In Ni80Fe20/Cr multilayered structures, both the magnitude of the interlayer magnetic exchange coupling and the saturation magnetoresistance have been found to oscillate with the Cr spacer layer thickness with a period of about 13 A. Ferromagnetic resonance (FMR) spectra have revealed that for antiferromagnetically (AF) coupled films ( t Cr = 12, 25 A ) there is a weak absorption mode of higher field than that of the regular in-phase mode, and that there are only some lower field resonance modes for ferromagnetically coupled films. Moreover, the magnetization vs temperature curves for the AF films have been found to have sizable thermal magnetic hysteresis. From the FMR spectrum for t Cr = 12 A and the temperature dependence of the magnetization in different magnetic fields for t Cr = 12, 25 A , the maximum strength of the AF coupling has been estimated to be about 0.017 erg cm-2.

Oscillatory interlayer exchange coupling in Ni80Fe20/Cr multilayers

Abstract Evidence of antiferromagnetic interlayer exchange coupling in Ni 80 Fe 20 /Cr multilayers is reported. In Ni 80 Fe 20 /Cr multilayers, both the magnitude of the interlayer magnetic exchange coupling and the saturation magnetoresistance have been found to oscillate with the Cr space layer thickness with a period of about 13 A. FMR spectra revealed a weak resonance mode above the regular in-phase mode for the antiferromagnetically coupled films, and only some lower-field resonance modes for ferromagnetically coupled films.

The magnetic anisotropy and interlayer magnetic coupling of evaporated Ag/Ni multilayers

Abstract A series of Ag/Ni multilayers has been prepared by e-beam deposition and studied by ferromagnetic resonance technique as a function of the static magnetic fied orientation in a plane perpendicular to the film plane. Interface mode has been observed in nearly perpendicular geometry for multilayers with Ni layer thicknesses less than 30 A. Interface anisotropy, which is parallel to the film plane, has been obtained and understood. Moreover, the effect of interlayer magnetic coupling on the ferromagnetic spectrum has been discussed.

Magnetic excitations in amorphous Sm-Ni thin films☆

Abstract The temperature dependence of magnetization has been studied for amorphous Sm x Ni 1 -x thin film alloys. It was found that both spin wave excitations and Stoner excitations occur in the temperature range 70–200 K, and a marked deviation from the T 3/2 law was noted below 70 K. Kaneyoshis theory was used to account for the deviation.

New permanent magnetic MnBiDy alloy films

We have studied the magnetic properties of MnBiDy films fabricated by the thermal coevaporation method and annealed subsequently in a vacuum oven at temperatures of 350 °C–425 °C. The thicknesses of these films are in the range from 60 to 1200 nm. X‐ray diffraction analyses have confirmed that those samples have an hcp structure. Magnetic measurements revealed that the saturation magnetization σs=46–78 emu/g, remanence ratio R=0.67–0.98, coercive force μHc=2.2–7.3 kOe, and magnetic energy product (BH)m=3.3–14.3 MGOe. These values are sensitive to the film thicknesses. It was found that μHc reaches a maximum at d≊400 nm.

Ferromagnetic resonance line width studies of Au/Co multilayers

Ferromagnetic resonance measurements on Au/Co multilayers have been performed as a function of the static magnetic field orientation in a plane perpendicular to the film plane. Besides a main mode, interface mode has been observed and explained by the appearance of interface anisotropy. Furthermore, a sharp dependence of line width on Au layer thickness has been discovered and explained by the effect of interlayer magnetic coupling over the Au layer.

Oscillatory Interlayer Magnetic Exchange Coupling Through Chromium Layers

The evidences of antiferromagnetic interlayer exchange coupling in Ni80Fe20/Cr multilayers are reported. In Ni80Fe20/Cr multilayers, both the magnitude of the interlayer magnetic exchange coupling and the saturation magnetoresistance were found to oscillate with the Cr spacer layer thickness with a period of about 13 A. Moreover, temperature dependence of magnetization shows a much larger thermal hysteresis for an antiferromagnetically coupled film than that for a ferromagnetically coupled film; in addition, zero magnetization occurs at 1.5 K in small magnetic field of 100 Oe for an antiferromagnetic film.

Low temperature magnetic excitations in amorphous light rare-earth-transition-metal thin films

Abstract The temperature dependence of magnetization has been studied on amorphous RT (R = Ce, Pr, Nd: T = Fe, Co, Ni) thin films. It was found that both spin wave excitations and band excitations exist for most RFe samples in temperature range T 0 –200K, and a marked deviation from Bloch T 3 2 is noted at T T 0 in all RT samples. T 0 is the temperature below which the T 3 2 law is unsuitable to describe the temperature dependence of the magnetization. T 0 ranges from 10 to 100 K. The deviation is accounted for the magnetic structure transition and can be explained by Kaneyoshis theory.