Mingxiao Zhang

Magnetic properties and martensitic transformation in quaternary heusler alloy of NiMnFeGa

Quaternary Heusler alloy Ni2(Mn,Fe)Ga has been studied systematically for the structure, martensitic transformation, and magnetic properties in two systems of Ni50.5Mn25−xFexGa24.5 and Ni50.4Mn28−xFexGa21.6. Substituting Fe for Mn up to about 70%, the pure L21 phase and the thermoelastic martensitic transformation still can be observed in these quaternary systems. Iron doping dropped the martensitic transformation temperature from 220 to 140 K, increased the Curie temperature from 351 to 429 K, and broadened the thermal hysteresis from about 7 to 18 K. Magnetic analysis revealed that Fe atoms contribute to the net magnetization of the material with a moment lower than that of Mn. The temperature dependence of magnetic-field-induced strains has been improved by this doping method.

Enhancement of glass-forming ability of Fe-based bulk metallic glasses with high saturation magnetic flux density

The effects of substituting Fe with Ni on thermal properties, glass-forming ability (GFA) and magnetic properties of Fe76-xNixMo3.5P10C4B4Si2.5 (x = 0−30 at.%) alloys were investigated in detail. The breadth of the supercooled liquid region was found to gradually increase from 42 to 55 K with increasing Ni content to 30 at.%. When x = 5 at.%, the alloy composition approached a eutectic point, resulting in an increase in GFA. As a result, FeNiMoPCBSi bulk metallic glasses with critical diameters up to 5.5 mm were successfully synthesized by copper mold casting. These glassy alloys exhibit a high saturation magnetic flux density of 0.75−1.21 T and excellent soft magnetic properties, i.e., low coercive force of 1.1−2.0 A/m, and high effective permeability of 14400−19700 at 1 kHz under a field of 1 A/m. The reasons for the high stability of the supercooled liquid, and the high GFA as well as excellent soft magnetic properties are discussed in this article.

Soft magnetic properties of bulk FeCoMoPCBSi glassy core prepared by copper mold casting

Bulk Fe66Co10Mo3.5P10C4B4Si2.5 glassy core of 10 mm in outer diameter, 6 mm in inner diameter, and 1 mm in thickness was successfully prepared by copper mold casting. The effects of annealing treatments on magnetic properties and microstructure of these cores were investigated. After an optimum annealing treatment, the resulting bulk glassy core exhibits good magnetic properties, i.e., high saturation magnetic flux density of 1.23 T, low coercive force of 1.0 A/m, high maximum permeability of 450u2009000, respectively. In addition, the glassy core also shows low core loss of 0.4 W/kg at 50 Hz and at maximum magnetic flux density of 1 T. The synthesis of bulk glassy core with excellent magnetic properties is encouraging for enlarging the application field of ferromagnetic bulk glassy alloys.

Detection of geometric phases in flux qubits with coherent pulses

We propose a feasible experimental scheme to demonstrate the geometric phase in flux qubits by means of a detuning coherent microwave pulse technique. Through measuring the probability of the persistent current state in the flux qubits, one can detect the Berry phase that is acquired with the systems Hamiltonian adiabatical circular evolution in the parameter space. Furthermore, we show that one could choose an appropriate amplitude of pulses in an experiment to obtain high readout resolution when the detuning frequency of the pulses is fixed, and controlled phase shift gates can be implemented based on the geometric phases by inductance coupling of two flux qubits.

Effect of Fe to P concentration ratio on structures, crystallization behavior, and magnetic properties in (Fe0.79+xP0.1-xC0.04B0.04Si0.03)99Cu1 alloys

The effect of Fe to P concentration ratio on structures, crystallization behavior, and magnetic properties in (Fe0.79+xP0.1−xC0.04B0.04Si0.03)99Cu1 alloys was investigated. The increase of Fe to P concentration ratio changes the structure and crystallization process of as-quenched ribbon. Nanocrystalline alloys with excellent soft magnetic properties were synthesized upon annealing the as-quenched ribbon with primary crystals. The (Fe0.84P0.05C0.04B0.04Si0.03)99Cu1 nanocrystalline alloy exhibits excellent magnetic properties, such as high saturation magnetic flux density of 1.74u2009T, low coercivity of 4.9u2009A/m, high effective permeability of 22xa0900 (at 1u2009kHz), low core loss of 3.1u2009W/kg at 1.0u2009T and 400u2009Hz, and 8.9u2009W/kg at 1.0u2009T and 1u2009kHz, respectively.

Large magnetoresistance in La2/3Ca1/3MnO3 thin films induced by metal masked ion damage technique

We have developed a simple process to obtain large magnetoresistance (MR) in perovskite manganite thin films by a combination of focused ion beam milling and 120keV H2+ ion implantation. Metal slits about 70nm in width were printed by 30kV focused Ga ion beam nanolithography on a 4μm track, and the materials in these slits are then irradiated by the accelerated H2+ ions. Using this method, in a magnetic field of 5T we can get a MR>60% over a 230K temperature scope, with a maximum value of 95% at around 70K. This technique is very promising in terms of its simplicity and flexibility of fabrication and has potential for high-density integration.