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731.
J. Ben Youssef S. Pogossian D.T. Dekadjevi 《Journal of magnetism and magnetic materials》2010,322(17):2593-2595
The dependence of the coercive field and saturated magnetization on the interfacial width is studied to understand the driving mechanism of the coercive enhancement in Fe/Mn and Co/Mn bilayers. We establish a controlled annealing procedure to reveal the origin of this enhancement. Using a model, we reveal that the full interfacial width plays a keyrole, and that no Mn based finite size effects drive the mechanism. We show that this mechanism is common to both type of bilayers. 相似文献
732.
S.K. Pradhan P.P. Rout D.K. Mishra A.K. Pradhan B.B. Nayak B.K. Roul 《Journal of magnetism and magnetic materials》2010,322(22):3614-3622
This paper reports that defect driven magnetism can be obtained at room temperature by optimizing metal ion concentration in bismuth ferrite (BFO) following our novel slow step solid state sintering route. We observed a clean signature of enhanced multiferroic behavior in Gd doped bismuth ferrite (Gd-BFO) bulk ceramics at room temperature (RT). Bismuth rich iron deficient Gd-BFO ceramics were prepared by solid state route through slow step sintering schedule at 850 °C. At particular composition, (Bi1.2Gd0.1Fe0.8O3), this materials completely transform from rhombohedral R3c to orthorhombic Pn21a space group. We emphasized that excess bismuth is expected to act as point defects and occupy interstitials positions, which in turn interact by oxygen vacancies. These defects are likely to promote defect driven ferromagnetism in BFO system. Incorporation of Gd in presence of excess bismuth in BFO enhanced both spin and electric polarization at room temperature. We also infer that Gd substitution in BFO is likely to suppress spiral spin modulation, which also favors ferromagnetism in Gd-BFO. 相似文献
733.
A. Bhattacharjee H. Mandal J. Kusz P. Gütlich 《Journal of magnetism and magnetic materials》2010,322(22):3724-3727
Stone dust sample collected from a stone crushing industry situated at Muhammad Bazar in Birbhum, India, is studied for its physical characterization using various techniques. Morphology and compositional analysis of the stone dust by scanning electron microscopy (SEM) reveal that the dust is an agglomeration of many tiny particles (0.32-2.12 μm), mostly having sharp edges, as well show microstructure heterogeneity. Elements present in the sample are detected by energy dispersive X-ray spectrometry (EDX). The X-ray diffraction (XRD) pattern analysis shows that the sample mainly contains minerals like anorthite, augite, esseneite and albite. An overall antiferromagnetic interaction in this sample has been indicated by the nature of the thermal dependence of magnetization. The remnant magnetization study apparently indicates two magnetic transitions at low temperatures. 57Fe Mössbauer spectroscopy has been employed to detect different possible iron sites as well as to estimate the respective site population. In general, Mössbauer spectroscopic results corroborate the observations made through XRD analysis in general. 相似文献
734.
Mechanical alloying has been used to produce nanocrystalline samples of Co2CrAl Heusler alloys. The samples were characterized by using different methods. The results indicate that, it is possible to produce L21-Co2CrAl powders after 15 h of ball-milling. The grain size of 15 h ball milled L21-Co2CrAl Heusler phase, calculated by analyzing the XRD peak broadening using Williamson and Hall approach was 14 nm. The estimated magnetic moment per formula unit is ∼2 μB. The obtained magnetic moment is significantly smaller than the theoretical value of 2.96 μB for L21 structure. It seems that an atomic disorder from the crystalline L21-type ordered state and two-phase separation depresses the ferromagnetic ordering in alloy. Also, the effect of annealing on the structural and magnetic properties of ball milled powders was investigated. Two structures were identified for annealed sample, namely L21 and B2. The obtained value for magnetic moment of annealed sample is smaller than the as-milled sample due to the presence of disordered B2 phase and improvement of phase separation. 相似文献
735.
We calculate the diamagnetic susceptibility in zero external magnetic field above the phase transition from ferromagnetic phase to phase of coexistence of ferromagnetic order and unconventional superconductivity. For this aim we use generalized Ginzburg-Landau free energy of unconventional ferromagnetic superconductor with spin-triplet electron pairing. A possible application of the result to some intermetallic compounds is briefly discussed. 相似文献
736.
The Ising approximation of the Heisenberg model in a strong magnetic field, with two, three and six spin exchange interactions is studied on a kagome chain. The kagome chain can be considered as an approximation of the third layer of 3He absorbed on the surface of graphite (kagome lattice). By using dynamical approach we have found one- and multi-dimensional mappings (recursion relations) for the partition function. The magnetization diagrams are plotted and they show that the kagome chain is separating into four sublattices with different magnetizations. Magnetization curves of two sublattices exhibit plateaus at zero and 2/3 of the saturation field. The maximal Lyapunov exponent for multi-dimensional mapping is considered and it is shown that near the magnetization plateaus the maximal Lyapunov exponent also exhibits plateaus. 相似文献
737.
L. Miu I. Ivan P. Badica G. Jakob D. Miu P. Mele K. Matsumoto M. Mukaida Y. Yoshida T. Horide A. Ichinose S. Horii 《Physica C: Superconductivity and its Applications》2010,470(20):1126-1129
The temperature T variation of the normalized magnetization relaxation rate S in high-temperature superconductors (HTS) with strong vortex pinning exhibits a maximum in the low-T range. This was reported for various HTS, and the origin of the faster relaxation at low T appearing in standard magnetization relaxation measurements was usually related to specific pinning properties of the investigated specimens. Since the observed behaviour seems to be characteristic to all HTS with enhanced pinning (generated by random and/or correlated disorder), we show that the S(T) maximum can be explained in terms of classic collective vortex creep. The influence of thermo-magnetic instabilities in the low-T range is also evidenced. The collective (elastic) creep regime is generated by the T dependent macroscopic currents induced in the sample during standard magnetization measurements. 相似文献
738.
J. Große 《Fortschritte der Physik》2008,56(3):183-301
739.