Zhai Hongru

Magnetic properties of heat treated Nd3Fe81B16 alloy

The hysteresis loop and Mossbauer spectrum of the heat treated Nd3Fe81B16 alloy ribbons annealing at 660° C for 10min. have been measured. A coercive field of about 2kOe and an energy product of about 8MGOe are obtained at room temperature. X-ray diffraction and Mossbauer spectrum analyses show that the high coercivity may originate from the Fe3B phase containing Nd. The value of remanence and energy product in this alloy are much higher than those of anisotropic BaFe12O19 ferrite. It may be used as a cheap permanent magnet.

Spin Wave Resonance in Fe/Cu Compositionally Modulated Films

Fe/Cu compositionally modulated films made by rf sputtering were investigated with ferromagnetic resonance. Spin wave resonances related to interlayer exchange coupling were observed and the phase change of the spin wave was shared by both the Fe and Cu sublayers. The effective spin wave dispersion coefficient was found to increase with increasing thickness of Cu sublayers.

Magneto-Optical Kerr Effect of Compositionally Modulated Co/Pt Films

In this paper the magneto-optical polar Kerr rotation spectra of compositionally modulated films (CMF) Co/Pt are calculated by using Fresnels equations. For CMF Co/Pt with dCo/dPt=1/2, 1 and 2 the magneto-optical Kerr rotation at any wavelength increases with the increasing modulation wavelength in the wavelength region from 200 to 800 nm. For CMF Co/Pt of constant dPt the Kerr rotation increases with dCo increasing while of constant dCo the Kerr rotation increases with dPt decreasing. From numerical calculations it is suggested that for CMF Co/Pt with small dPt the Pt sublayer is polarized and has a positive contribution to the Kerr rotation of CMF Co/Pt.

Enhancement of Kerr rotation of thin Fe films

The magneto-optical Kerr rotation spectra in the region 400-700nm is studied for single layer Fe films. Experimental and theoretical calculation show that in the whole measurement wavelength range an enhancement of Kerr rotation occurs when the thickness of Fe is smaller than about 150A. The thickness dependence of Kerr rotation of single layer Fe and Fe/Cu bilayer is compared. It is concluded that the Kerr rotation is dependent sensitively on the optical constants of underlying materials and the thickness of magnetic layer.

Model of hybrid interfacial domain wall in ferromagnetic/antiferromagnetic bilayers*

A general model of a hybrid interfacial domain wall (HIDW) in ferromagnetic/antiferromagnetic exchange biased bilayers is proposed, where an interfacial domain wall is allowed to extend into either the ferromagnetic or antiferromagnetic layer or across both. The proposition is based on our theoretical investigation on thickness and field dependences of ferromagnetic domain wall (FMDW) and antiferromagnetic domain wall (AFDW), respectively. Good match of the simulation to the hysteresis loops of a series of NiFe/FeMn exchange-biased bilayers confirms the existence of the HIDW, where the AFDW part is found to preferentially occupy the entire antiferromagnetic layer while the FMDW shrinks with the increased magnetic field as expected. The observed asymmetry between the ascending and descending branches of the hysteresis loop is explained naturally as a consequence of different partition ratios between AFDW and FMDW.

Magnetic properties of FeMnSiB amorphous alloys

The Fe(82-x)Mn(x)Si(5)B(13) (x=0-6) amorphous alloy system was investigated by magnetic measurements, X-ray diffraction, small angle X-ray scattering, differential scanning calorimetry, resistivity measurement and mossbauer spectra. By addition of Mn the thermal stability and core loss of FeSiB alloys were improved. The over-all properties of FeMnSiB alloys appeared to be better than those of the FeCrSiB system. The relation between Hc, μ, and size of precipitates during early crystallization was found that Hc was maximum and μ, was minimum at one particle size. The relative values of exchange integrals between different adjacent atoms determined by fitting the cubic equation of Tc from CPA theory with experimental data, were different from those in other system containing Mn. A strong Kondo-like effect was observed in this system.

Calculation of magnetocrystalline anisotropy of Nd2Fe14B

The contribution of Nd3+ ions to the magnetocrystalline anisotropy of intermetallic compound Nd2Fe14B was calculated by single ion theory. The results explained the high anisotropy of Nd-Fe-B alloy. By adjusting the shielding factors the calculated K1-T and K2-T relations agree with the experimental curves.

A RKKY Model Fitting of Nuclear Magnetic Resonance Spectra of 63Cu in Fe/Cu Multilayers

In this letter, a theoretical fit of nuclear magnetic resonance spectra of 63Cu in Cu layers of Fe/Cu Multilayers is given based on RKKY theory. The values of exchange field and additional Knight shift are fitted, which agree approximately with the experimental data.

Structure and Magnetic Properties of Sputtered Bi2DyFe5O12 Films

The effects of the annealing temperature and time on the structure and magnetic properties of the sputtered BiDy-iron garnet films were investigated. X-ray diffraction analysis shows that the as-sputtered films are amorphous. After annealing at about 550°C, amorphous films crystallize into the garnet phase and an unknown phase. The intensity of the unknown phase decreases with increasing annealing temperature and time and vanishes at 650°C for 30 min. It is found that the unknown phase has a large influence on the half-width of the (420) x-ray diffraction peak. The as-sputtered films have a very small magnetization of about 1 emu/g at room temperature. When films are annealed above 570°C, the magnetization increases rapidly with increasing annealing temperature and time.

On the magnetocrystalline anisotropy of Pr-transition metal intermetallics

Abstract The contribution of the Pr 3+ ions to the magnetocrystalline anisotropy constants K 1 and K 2 in Pr 2 Fe 14 B as well as its temperature dependence have been calculated within a single-ion theory. The calculated results agree with experiment. The anisotropy constants due to the Pr 3+ ions in PrCo 5 were also calculated. By considering all terms of the crystal field (CF), including the Co contribution, we obtained results which were again in good agreement with experiment.