Ziqian Wang

Magnetic properties and structural phase transformations of NiMnGa alloys

The magnetic properties and structural phase transformations of Heusler alloys Ni/sub 2+x/Mn/sub 1-x/Ga and Ni/sub 2-x/Mn/sub 1+x/2/Ga/sub 1+x/2/ were investigated. It was found that the martensitic transformation temperature increases and the Curie temperature decreases with decreasing Mn concentration in the Ni/sub 2+x/Mn/sub 1-x/Ga system, but the magnetic properties decrease faster than those do in the Ni/sub 2-x/Mn/sub 1+x/2/Ga/sub 1+x/2/ system. This suggests that the influence of the conduction electron concentration and the distance between Mn atoms on the Curie temperature is stronger than the magnetic dilution effect. The martensitic transformation temperature shows a peak value at x=0.06 in the Ni/sub 2-x/Mn/sub 1+x/2/Ga/sub 1+x/2/ system. A large stress-free magnetic-field-induced strain (MFIS) of 1.8% has been obtained at room temperature in a single crystal sample with the composition of the first system.

The mechanism of the photoresponse blueshifts for the n-type conversion region of n(+)-on-p Hg0.722Cd0.278Te infrared photodiode

The photoresponse blueshift of the n-type conversion region for n+-on-p Hg0.722Cd0.278Te infrared photodiode is numerically investigated by considering the conduction band nonparabolic characteristic and band gap narrowing effect. It has been shown that the photoresponse position of the n-type conversion region shifts remarkably toward high energy. The shift energy is 37 meV higher than that of the p region. The result can be used to explain quantitatively the recent experimental observation of the blueshift of the photoluminescence peak for the n-type conversion region. The following three contributions are considered: (i) the Burstein–Moss shift considering a nonparabolic conduction band, (ii) the band gap narrowing effect, and (iii) the Hg-vacancy-induced acceptor trap level. It is concluded that the band gap narrowing and nonparabolic effects play an important role in the photoresponse of n+-on-p HgCdTe infrared photodiode with heavy doping concentration.

Magnetization characteristic of ferromagnetic thin strip by measuring anisotropic magnetoresistance and ferromagnetic resonance

Abstract The magnetization characteristic in a Permalloy thin strip is investigated by electrically measuring the anisotropic magnetoresistance and ferromagnetic resonance in in-plane and out-of-plane configurations. Our results indicate that the magnetization vector can rotate in the film plane as well as out of the film plane by changing the intensity of external magnetic field of certain direction. The magnetization characteristic can be explained by considering demagnetization and magnetic anisotropy. Our method can be used to obtain the demagnetization factor, saturated magnetic moment and the magnetic anisotropy.

The magnetic phase diagram of DyFe12-xMox (1.00 <= x <= 3.00)

The magnetocrystalline anisotropy and magnetic structure of DyFe12−xMox (1.00≤x≤3.00) have been investigated in detail by X-ray diffraction, thermomagnetic analysis, AC magnetic susceptibility, singular point detection technique and angular-magnetization measurement. A magnetic phase diagram of DyFe12−xMox (1.00≤x≤3.00) has been proposed. At room temperature, all DyFe12−xMox compounds exhibit uniaxial anisotropy. At low temperature, a spin reorientation transition of axis-to-cone was observed for DyFe12−xMox compounds with low Mo concentration, x<2.00. The spin reorientation temperature decreases with increasing Mo concentration. For DyFe12−xMox compounds with high Mo concentration, magnetohistory effects were observed below 48 K.

Microwave-Induced DC Response of Spin Wave Resonance Driven by an Anisotropic Built-In Field in a Permalloy Thin Strip

The microwave-induced dc response has been investigated in an in-plane magnetized permalloy strip. The spin wave resonances (SWRs) are observed. The SWR signals get anomalously suppressed when the direction of the specimen or the amplitude of the microwave frequencies is changed. Such suppression occurs at frequencies of less than 11 GHz, while the resonant field is as weak as less than 200 Oe. They are finally quantitatively interpreted by introducing an anisotropic built-in magnetic field that describes the shape anisotropy of the specimen.

Magnetic properties of Y2Fe15Cr2 single crystal

A Y2Fe15Cr2 Single crystal with the Th2Ni17-type structure has been prepared by the Czochralski method and investigated by means of Laue back-reflection, metallographic observation, X-ray diffraction, the singular point detection technique and magnetic measurements. A magnetohistory effect has been observed at a low temperature. Magnetization curves have been measured along the easy and hard directions in fields up to 6.5 T, The saturation magnetization and magnetocrystalline anisotropy field decrease with increasing temperature. The experimental magnetocrystalline anisotropy constant is in good a,areement with the calculation results on first approximation

A study of the magnetocrystalline anisotropy of Sm1−xDyxFe10.5Mo1.5(x = 0–1.0)

The magnetocrystalline anisotropy and the spin reorientation of Sm1−xDyxFe10.5Mo1.5 were investigated in detail. At room temperature, all Sm1−xDyxFe10.5Mo1.5 alloys possess easy c-axis anisotropy and the magnetocrystalline anisotropy field decreases with increasing Dy concentration. However, at low temperature, a spin reorientation transition of axis-to-cone type was observed in the Sm1−xDyxFe10.5Mo1.5 alloys with xu2009≥u20090.8. The spin reorientation temperatures increase with increasing Dy concentration in the Sm1−xDyxFe10.5Mo1.5 alloys.

Ferromagnetic Resonance Line Shapes in Permalloy Strips at Low Magnetic Fields

Spin rectification line shapes for ferromagnetic resonance in swept, low external bias fields differ significantly from widely investigated high-field resonant spectra. The anomaly in the low-field case may originate from magnetization rotation associated with magnetic anisotropy and demagnetization. The low-field, rectified voltage spectra are also sensitive to the relative phase and polarization of the microwave field. Ferromagnetic thin strips thus have the potential for use as polarization- and phase-resolved microwave detectors at low fields.